Research Article A Statistical Cohomogeneity One Metric on...
Transcript of Research Article A Statistical Cohomogeneity One Metric on...
Research ArticleA Statistical Cohomogeneity One Metric onthe Upper Plane with Constant Negative Curvature
Limei Cao1 Didong Li2 Erchuan Zhang2 Zhenning Zhang3 and Huafei Sun2
1School of Mathematics and Physics University of Science and Technology Beijing Beijing 100083 China2School of Mathematics and Statistics Beijing Institute of Technology Beijing 100081 China3College of Applied Sciences Beijing University of Technology Beijing 100124 China
Correspondence should be addressed to Huafei Sun huafeisunbiteducn
Received 24 September 2014 Revised 15 December 2014 Accepted 15 December 2014 Published 30 December 2014
Academic Editor Carlo Cattani
Copyright copy 2014 Limei Cao et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
we analyze the geometrical structures of statistical manifold S consisting of all the wrapped Cauchy distributionsWe prove that S isa simply connected manifold with constant negative curvature119870 = minus2 However it is not isometric to the hyperbolic space becauseS is noncomplete In fact S is approved to be a cohomogeneity one manifold Finally we use several tricks to get the geodesics andexplore the divergence performance of them by investigating the Jacobi vector field
1 Introduction
So far more and more geometric approaches have beenapplied to various fields such as in statistics physics andcontrol [1ndash6] by analyzing their complexity characterizationsor giving their solutions
Entropic dynamics is a theoretical framework con-structed on statistical manifolds to explore the possibilityof laws of physics [7] Until now researchers have triedto study a variety of entropic dynamic models from theviewpoint of information geometry [4ndash6 8] In [8] twoentropic dynamical models are considered in which the sta-bility of the Jacobi vector fields on Riemannian manifolds isinvestigated In [4] authors explored the geometric structuresand instability of entropic dynamical models Informationgeometric characterization of fractional Brownian motionswas considered in [5] Hamiltonian dynamics are studiedfrom the viewpoint of geometry in [6]
In probability theory and directional statistics [9] awrapped probability distribution is a continuous probabilitydistribution whose state can be considered as lying on a unit119899-sphere 119878
119899 Examples include the Bingham distribution [10]the Kent distribution (or the Fisher-Bingham distribution)[11] and the vonMises-Fisher distribution [9 12] Particularlyfor one-dimensional cases a wrapped distribution consists
of points on the unit circle For instance a wrapped Cauchydistribution [9 13 14]
119901 (119909 120583 120574) =1
2120587
sinh 120574
cosh 120574 minus cos (119909 minus 120583)(1)
is a wrapped probability distribution that results from theldquowrappingrdquo of the Cauchy distribution around the unit circlewhere apparently 119909 isin [minus120587 120587) which is parameterized fromthe unit circle 120574 isin 119877 and 120583 gt 0 The functions sinhand cosh are respectively the hyperbolic sine function andthe hyperbolic cosine function As the random variable 119909 isin
[minus120587 120587] the wrapped probability distribution can be con-sidered as an angular probability to measure the directionalprobabilityTherefore it has beenwidely applied in the field ofrandomwalk for studying animalmovements [15 16] such asidentifying fishing trip behavior and estimating fishing effort[17] and ringing recoveries of pied flycatchers [18]
Assume that all information relevant to dynamical evolu-tion of the model can be obtained from the associated proba-bility distribution which is the wrapped Cauchy distributionin our consideration We will call this model the WCED(wrapped Cauchy entropic dynamical) model for simplicity
The remainder of the paper is organized as follows InSection 2 the geometric structures including the Fishermet-ric and the sectional curvature of the WCED are calculated
Hindawi Publishing CorporationAdvances in Mathematical PhysicsVolume 2014 Article ID 832683 6 pageshttpdxdoiorg1011552014832683
2 Advances in Mathematical Physics
In Section 3 this manifold is proved to be simply connectedbut not complete hence not isometric to the hyperbolic spaceHowever it is proved to be a cohomogeneity one manifoldby Theorem 14 In Section 4 several tricks are used basedon some special properties to get geodesics and the Jacobivector fields The geodesics are the sets of fixed points ofisometric transformations which include symmetries to linesparalleled to 119910-axis Meanwhile the Jacobi vector fields arecalculated Then the instability of the geodesic spreads isanalyzed via the behaviors of the the Jacobi vector field
Remark 1 It is well known that the upper plane R2+admits a
hyperbolic metric 119892119867with constant negative curvature That
is
119892119867
=
[[[
[
1
11991020
01
1199102
]]]
]
(2)
However in this paper we give another metric on R2+
with constant negative curvature but not isometric to thehyperbolic space
2 Geometric Structures of the WCED Model
From the theory of information geometry one can definean 119898-dimensional statistical manifold 119872 over unit sphereswhich is a set of probability densities namely
119872 = 119901 (119909 120579) (3)
The parameter 120579 = (1205791
1205792
120579119898
) plays the role of coordi-nate systems The Fisher information matrix 119892 acting as aRiemannian metric is then given by the expectation
(119892119894119895) = (119864 [(120597
119894119897) (120597119895119897)]) (4)
where 119897(119909 120579) = ln119901(119909 120579) and 120597119894
= 120597120597120579119894 On a statistical
manifold the Riemannian connection coefficient Γ119894119895119896
is (seeeg [1 2 19ndash21])
Γ119894119895119896
= 119864 [(120597119894120597119895119897) (120597119896119897)] +
1 minus 120572
2119864 [(120597119894119897) (120597119895119897) (120597119896119897)] (5)
which can be expressed as a classical formula Γ119894119895119896
=
(12)(120597119894119892119895119896
+ 120597119895119892119896119894
minus 120597119896119892119894119895) equivalently
If (1205791
1205792
120579119898
) is a local coordinate of 119872 then forany vector field 119883 on 119872 one has 119883 = 119883
119894
120597119894 where 119883
119894
are smooth functions with respect to (1205791
1205792
120579119898
) TheEinstein summation convention is used here and all throughthe paper With the Riemannian connection the curvaturetensor is defined by [19 20]
119877 (119883 119884) 119885 = nabla119883
nabla119884119885 minus nabla
119884nabla119883
119885 minus nabla[119883119884]
119885 (6)
and the Riemannian curvature tensor is
119877 (119883 119884 119885 119882) = 119892 (119877 (119885 119882) 119883 119884) (7)
where 119883 119884 119885 119882 are smooth vector fields on 119872 and [sdot sdot]
represents the Lie bracket namely [119883 119884] = 119883 ∘ 119884 minus 119884 ∘ 119883The local representation of the curvature tensor satisfies
119877119898119895119896119897
= (120597119898
Γ119905
119895119896minus 120597119895Γ119905
119898119896) 119892119905119897
+ (Γ119898119905119897
Γ119905
119895119896minus Γ119895119905119897
Γ119905
119898119896) (8)
where Γ119896
119898119895= Γ119898119895119905
119892119905119896 and (119892
119905119896
) is the inverse of the metricmatrix (119892
119905119896)
The Ricci curvature and the sectional curvature aredefined by
119877119898119896
= 119877119898119895119897119896
119892119895119897
(9)
119870119894119895
= minus
119877119894119895119894119895
119892119894119894119892119895119895
minus 1198922
119894119895
(10)
respectivelyA curve 120585(119905) on 119872 is said to be a geodesic if its tangent
vector 120585(119905) is displaced parallel along the curve 120585(119905) that is
nabla 120585(119905)
120585 (119905) = 0 (11)
and it has the following local form
d2120579119896
d1199052+ Γ119896
119895119898
d120579119895
d119905
d120579119898
d119905= 0 (12)
Suppose that the solution of (12) is 120579(119905 120573) where 120573 is a vectorwhose components are the integration constants
Considering the wrapped Cauchy entropic dynamicalmodel the corresponding statistical manifold is
119878 = 119901 (119909 120579) | 120579 = (1205791
1205792
) isin R2
+ (13)
where 119901(119909 120579) is given by (1) with parameters 1205791
= 120583 and 1205792
=
120574 The Fisher information matrix can be easily calculated as
119892 = diag (1
2sinh21205792
1
2sinh21205792) (14)
Proposition 2 Thenonzero components of the Ricci curvatureare
11987711
= 11987722
= minus1
sinh21205792 (15)
Proof A direct calculation of (5) gives the nonvanishingRiemannian connection coefficients
Γ112
= minusΓ121
= minusΓ211
= minusΓ222
=cosh 120579
2
2sinh31205792 (16)
From the relation Γ119896
119898119895= Γ119898119895119905
119892119905119896 one can get another type of
connection coefficients
Γ2
11= minusΓ1
12= minusΓ1
21= minusΓ2
22=cosh 120579
2
sinh 1205792 (17)
From (8) the following nonzero component of the curvaturetensor is obtained
1198771212
=1
2sinh41205792 (18)
Therefore the proof can be finished by a simple substitutionof (18) into (9)
Advances in Mathematical Physics 3
The following theorem is obtained by substituting (18)and (14) into (10)
Theorem 3 119878 is a manifold with constant negative curvature119870 = minus2
3 Topological and Geometric Properties of 119878
Lemma 4 119878 is diffeomorphic to R2+and hence simply con-
nected
Proof The topology as well as the smooth structure of 119878 isinduced by those onR2
+ hence 119878 is diffeomorphic toR2
+ The
fact that R2+is simply connected implies that 119878 is also simply
connected
If 119878 were also complete it would be a space formwith constant negative curvature which was isometric tothe hyperbolic space 119867
2
(minus2) However 119878 is not completeWe begin with a necessary and sufficient condition of thecompleteness
Definition 5 (see [19]) Let (119872 119892) be a RiemannianmanifoldA smooth curve 120574 [0 +infin) rarr 119872 is called a divergent curveif for any compact subset 119870 sub 119872 there exists 119905
0gt 0 st
120574(1199050) notin 119870 If 120574 is a divergent curve its length is defined by
119871 (120574) = lim119904rarr+infin
int
119904
0
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905 (19)
Lemma 6 (see [22]) (119872 119892 119889) is a connected Riemannianmanifold then 119872 is complete if and only if every divergentcurve has infinite length
Proof (1) Suppose that 119872 is complete and 120574 is a divergentcurve Consider
119881119899
= 119901 isin 119872 | 119889 (119901 120574 (0)) le 119899 forall119899 isin N (20)
where for each 119899 119881119899is bounded and closed hence compact
The divergence of 120574 implies that for all 119899 isin Nlowast exist119905119899
ge 0 st120574(119905119899) notin 119881119899 As a result
int
119905119899
0
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905 ge 119889 (120574 (0) 120574 (119905
119899)) ge 119899 (21)
hence 119871(120574) = +infin(2) Suppose every divergent curve has infinite length
Assume that 119872 is noncomplete which implies that exist119901 isin 119872existV0
isin 119879119901119872 and 120574(119905) = exp
119901(119905V0) is only defined on 119905 isin [0 1)
119871(120574) lt |V0| lt +infin means 120574 is not divergent that is there
exists a compact subset 119870 sub 119872 st 120574(119905) isin 119870 for all 119905 Choosesequence 119905
119899+infin
119899=1 st 119905
119899rarr 1 and 119905
119899lt 119905119899+1
for all 119899 isin N It isobvious that 119889(120574(119905
119899) 120574(119905119898
)) rarr 0 when 119899 119898 are sufficientlylarge Hence 120574(119905
119899) is a Cauchy sequence The completeness
of 119872 implies that there exists 119902 isin 119870 st 120574(119905119899) rarr 119902
Then 120574(1) = 119902 is a extension of 120574 from [0 1) to [0 1]
which contradicts to the assumption which implies that119872 isin fact complete
Theorem 7 119878 is noncomplete
Proof Suppose that 120574(119905) = (0 119905) isin R2+ 119905 isin [1 +infin) is a curve
along the 119910-axis It is obvious that 120574 is divergent Howeverthe length of 120574 satisfies
119871 (120574) = int
+infin
1
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905
= int
+infin
1
1
radic2 sinh (119905)
d119905
=1
radic2
ln(tanh(119905
2))
1003816100381610038161003816100381610038161003816
+infin
1
=ln (119890 + 1) minus ln (119890 minus 1)
radic2
lt +infin
(22)
This implies 119878 is noncomplete by Lemma 6
Although 119878 is neither isometric to the hyperbolic spacenor a symmetric space it is ldquopartly symmetricrdquo which ispresented in Lemma 10
Definition 8 Let 119868(119878) be the group of isometric transforma-tions on 119878 A family of transformations on 119878 are defined as
120593120572
119878 997888rarr 119878 (1205791
1205792
) 997891997888rarr (2120572 minus 1205791
1205792
) forall120572 isin R
(23)
Remark 9 120593120572is just the reflection about the line 120579
1
= 120572which is a line parallel to the 119910-axis
Lemma 10 120593120572
isin 119868(119878) for all 120572 isin R
Proof For any fixed 120572 isin R for all 119901 = (1205791
1205792
) isin 119878 119902 =
120593120572(119901) = (2120572 minus 120579
1
1205792
)Consider
1205741
(119905) = (1205791
+ 119905 1205792
) 1205742
(119905) = (1205791
1205792
+ 119905)
(120593120572)lowast119901
(120597
1205971205791) =
dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(120593120572
∘ 1205741
(119905))
=dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(2120572 minus 1205791
minus 119905 1205792
) = minus120597
1205971205791
10038161003816100381610038161003816100381610038161003816119902
(120593120572)lowast119901
(120597
1205971205792) =
dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(120593120572
∘ 1205742
(119905))
=dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(2120572 minus 1205791
1205792
+ 119905) =120597
1205971205792
10038161003816100381610038161003816100381610038161003816119902
119892119902
((120593120572)lowast119901
(120597
1205971205791) (120593120572)lowast119901
(120597
1205971205791))
= 119892119902
(minus120597
1205971205791 minus
120597
1205971205791) =
1
2sinh21205792= 119892119901
(120597
1205971205791
120597
1205971205791)
4 Advances in Mathematical Physics
119892119902
((120593120572)lowast119901
(120597
1205971205791) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(minus120597
1205971205791
120597
1205971205792) = 0 = 119892
119901(
120597
1205971205791
120597
1205971205792)
119892119902
((120593120572)lowast119901
(120597
1205971205792) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(120597
1205971205792
120597
1205971205792) =
1
2sinh21205792= 119892119901
(120597
1205971205792
120597
1205971205792)
(24)
Hence 120593120572is an isometry
As a result 119866 = 120593120572
| 120572 isin R is a subgroup of 119868(119878)Lemma 10 implies that 119878 is ldquoalmostrdquo homogeneous althoughnot truly homogeneous In fact 119878 is a cohomogeneity onemanifold defined in Definition 11
Definition 11 Let (119872 119892) be a Riemannianmanifold and 119868(119872)
is its group of isometric transformations Then 119868(119872) has anatural action Φ on 119872
Φ 119868 (119872) times 119872 997888rarr 119872 (120593 119901) 997891997888rarr 120593 (119901)
forall120593 isin 119868 (119872) 119901 isin 119872
(25)
119872 is a cohomogeneity one manifold if the codimension oforbit space of this action is 1
Remark 12 The codimension of the orbit space is closelyrelated to the homogeneous properties For example if 119872 isa homogeneous space then the orbit space is whole manifold119872 and hence its codimension is 0The less that codimensionis the more homogeneous the manifold is In other wordsa cohomogeneity one manifold is ldquothe most homogeneousmanifoldrdquo except for the real ones
Actually cohomogeneity one manifolds are natural gen-eralizations of homogeneousmanifoldsThe systematic studyof cohomogeneity onemanifolds was started by Bergery whosuccessfully constructed new invariant Einstein metrics oncohomogeneity one manifolds In addition Bryant and Sala-mon constructed special metrics with exceptional holonomygroups 119866
2and Spin(7) on these manifolds [23ndash30]
We state a well known result without proof beforeTheorem 14
Lemma 13 Every homogeneous space is complete
Theorem 14 119878 is a cohomogeneity one manifold
Proof Let 119901 = (1205791
1205792
) isin 119878 and 119868(119878)119901
= 120593(119901) | 120593 isin 119868(119878)
be its orbit space If dim(119868(119878)119901) = 2 119878 will be homogeneous
Lemma 13 implies that 119878 is complete which contradicts toTheorem 7 This contradiction implies dim(119868(119878)
119901) le 1
On the other hand
119866119901
= 120593 (119901) | 120593 isin 119866 = 120593120572
(119901) | 120572 isin R
= (2120572 minus 1205791
1205792
) | 120572 isin R = (119909 1205792
) | 119909 isin R
(26)
Since 119866 is a subgroup of 119868(119878) 119866119901
sub 119868(119878)119901 This implies that
dim (119868 (119878)119901) ge dim (119866
119901) = 1 (27)
Based on the two inequalities we conclude that dim(119868(119878)119901) =
1 hence its codimension is 1 which means that 119878 is acohomogeneity one manifold
4 Instability Analysis
In this section we will calculate some geodesics and investi-gate the instability of the geodesics by the Jacobi vector fields
Combining (12) and (17) the geodesic equations of theWCED model are given by the following differential system
d21205791
d1199052minus
2 cosh 1205792
sinh 1205792
d1205791
d119905
d1205792
d119905= 0
d21205792
d1199052+cosh 120579
2
sinh 1205792(d1205791
d119905)
2
minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(28)
Generally these equations are quite hard to be solvedhowever we can get some special geodesics based on thecohomogeneity one property
Lemma 15 All lines parallel to the y-axis are geodesics
Proof It is well known that the fixed-points set of anyisometry is a geodesic Since 120593
120572is an isometry and its fixed-
points set is the line 119909 = 1205791 the lemma follows
According to Lemma 15 the equation of such geodesicsatisfies
1205791
= 1205791
0 (29)
Hence (28) can be reduced to
d1205791
d119905= 0
d21205792
d1199052minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(30)
Then solution is expressed as
1205791
= 1198863
1205792
= ln100381610038161003816100381610038161003816100381610038161003816
1198862exp 119886
1119905 + 1
1198862exp 119886
1119905 minus 1
100381610038161003816100381610038161003816100381610038161003816
(31)
Consider the parameter family of geodesics
F (119862) = 120579119897
(119905 119862)119897=12
(32)
where 120579119897 is a geodesic satisfying (28) and 119862 is an integration
constant vectorThe length of geodesics inF(119862) is defined as
Θ (119905 120573) = int (119892119894119895d120579119894d120579119895
)12
(33)
Advances in Mathematical Physics 5
Therefore the length of geodesics on WCED model isobtained as
Θ (119905 119862) = int
119905
0
radic11989211
(d1205791
d119905)
2
+ 11989222
(d1205792
d119905)
2
d120591 =radic21198621
2119905
(34)
where 1198621is constant In order to investigate the behavior of
two neighboring geodesics labeled by the parameter 1198621 we
consider the following difference
ΔΘ = (
radic2 (1198621
+ 1205751198621)
2minus
radic21198621
2) 119905 (35)
It is clear that ΔΘ diverges that is the length of twoneighboring geodesics with slightly different parameters 119862
1
and 1198621
+ 1205751198621differs in a remarkable way as 119905 rarr infin
The stability of the geodesics is completely determinedby the curvature of manifold Studying the stability ofdynamics means determining the evolution of perturbationsof geodesics For isotropic manifolds the geodesic spreadis unstable only if their constant sectional curvatures arenegative As long as the curvatures are negative the geodesicspread is unstable even if the manifold is no longer isotropic[19] However it is more attractive to know the divergentdegree of a geodesic
The Jacobi vector field 119869 that is the evolution perturba-tion vector satisfies the following (Jacobi) equation
nabla 120585(119905)
nabla 120585(119905)
119869 = 119877 ( 120585 (119905) 119869) 120585 (119905) (36)
where 120585(119905) is a geodesic on manifold 119872 It is also called thegeodesic derivation equation as it has close connections withthe geodesic In general the Jacobi equations are difficult tosolve but in particular this manifold has a constant negativecurvature which is of great help Given a normal geodesic 120585
and supposing 119869 is a normal Jacobi vector field along 120585(119905) then
119877 ( 120585 (119905) 119869) 120585 (119905) = 2 (119892 ( 120585 (119905) 120585 (119905)) 119869 minus 119892 ( 120585 (119905) 119869) 120585 (119905))
= 2119869
(37)
Thus the Jacobi equation is reduced to
d2119869 (119905)
d1199052minus 2119869 (119905) = 0 (38)
Choose a unit orthogonal frame 119890119894(119905) st 119890
2(119905) = 120585(119905) and
suppose
119869 (119905) = 119869119894
(119905) 119890119894(119905) (39)
Then the Jacobi equation satisfies
d21198691 (119905)d1199052
minus 21198691
(119905) = 0
1198692
(119905) = 0
(40)
The solutions are
1198691
(119905) = 1198621119890radic2119905
+ 1198622119890minusradic2119905
1198692
(119905) = 0
(41)
This means that the geodesic spread onmanifold is describedby means of an exponential order divergent Jacobi vectorfield
5 Conclusion and Remarks
In this paper we investigate the manifold of wrapped Cauchydistributions By considering the geometric structures of theWCED we conclude that the WCED is a constant negativecurvature space with119870 = minus2 By a series of lemmas and theo-rems we prove that it is a cohomogeneity one manifold Thisexample is interesting because of its statistical backgroundwhile some other examples are deliberately constructed Inaddition we calculate the geodesics and the Jacobi vector fieldby some tricks based on some special properties of 119878 As aresult the divergent behavior of geodesics can be describedas an exponential order divergent Jacobi vector field
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Authorsrsquo Contribution
The authors declare that the study was realized in collab-oration with the same responsibility All authors read andapproved the final paper
Acknowledgments
This work is supported by the National Natural ScienceFoundations of China (nos 11126161 and NSFC61440058)Beijing Higher Education Young Elite Teacher Project (noYETP 0388) and the Fundamental Research Funds for theCentral Universities (no FRF-BR-12-005)
References
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[2] S Amari and H Nagaoka Methods of Information Geo metryOxford University Press Oxford UK 2000
[3] T Li L Peng and H Sun ldquoThe geometric structure of theinverse gamma distributionrdquo Beitrage zur Algebra und Geome-trie vol 49 no 1 pp 217ndash225 2008
[4] L Peng H Sun D Sun and J Yi ldquoThe geometric structuresand instability of entropic dynamical modelsrdquo Advances inMathematics vol 227 no 1 pp 459ndash471 2011
[5] L Peng H Sun and G Xu ldquoInformation geometric charac-terization of the complexity of fractional Brownian motionsrdquoJournal of Mathematical Physics vol 53 no 12 Article ID123305 12 pages 2012
6 Advances in Mathematical Physics
[6] L Peng H Sun and X Sun ldquoGeometric structure of Hamilto-nian dynamics with conformal Eisenhart metricrdquo InternationalJournal of Mathematics and Mathematical Sciences vol 2011Article ID 710274 26 pages 2011
[7] A Caticha ldquoEntropic dynamicsrdquo in Bayesian Inference andMaximum Entropy Methods in Science and Engineering R LFry Ed AIP Conference Proceedings pp 617ndash302 2002
[8] C Cafaro and S A Ali ldquoJacobi fields on statistical manifolds ofnegative curvaturerdquo Physica D Nonlinear Phenomena vol 234no 1 pp 70ndash80 2007
[9] K V Mardia and P E Jupp Directional Statistics JohnWiley ampSons New York NY USA 1999
[10] C Bingham ldquoAn antipodally symmetric distribution on thesphererdquoThe Annals of Statistics vol 2 pp 1201ndash1225 1974
[11] J T Kent ldquoThe Fisher-Bingham distribution on the sphererdquoJournal of the Royal Statistical Society vol 44 pp 71ndash80 1982
[12] R A Fisher ldquoDispersion on a sphererdquo Proceedings of the RoyalSociety of London A vol 217 pp 295ndash305 1953
[13] N I Fisher Statistical Analysis of Circular Data CambridgeUniversity Press Cambridge UK 1996
[14] G Borradaile Statistics of Earth Science Data Springer NewYork NY USA 2003
[15] K A Keating and S Cherry ldquoModeling utilization distributionsin space and timerdquo Ecology vol 90 no 7 pp 1971ndash1980 2009
[16] H-I Wu B-L Li T A Springer and W H Neill ldquoModellinganimal movement as a persistent random walk in two dimen-sions expected magnitude of net displacementrdquo EcologicalModelling vol 132 no 1-2 pp 115ndash124 2000
[17] Y Vermard E Rivot S Mahevas P Marchal and D GascuelldquoIdentifying fishing trip behaviour and estimating fishing effortfrom VMS data using Bayesian Hidden Markov ModelsrdquoEcological Modelling vol 221 no 15 pp 1757ndash1769 2010
[18] K Thorup J Raboslashl and J J Madsen ldquoCan clock-and-compassexplain the distribution of ringing recoveries of pied flycatch-ersrdquo Animal Behaviour vol 60 no 2 pp F3ndashF8 2000
[19] M P do Carmo Riemannian Geometry Birkhauser BostonMass USA 1992
[20] P Petersen Riemannian Geometry Springer New York NYUSA 2nd edition 2006
[21] C R Rao ldquoInformation and the accuracy attainable in theestimation of statistical parametersrdquo Bulletin of the CalcuttaMathematical Society vol 37 pp 81ndash91 1945
[22] W Chen and X Li Introduction to Riemannian GeometryPeking University Press Beijing China 2012
[23] D Alekseevsky ldquoRiemannian manifolds of cohomogeneityonerdquo in Proceedings of the Colloquium on Differential Geometryvol 56 of Colloeq Math Soc J Bolyai pp 9ndash22 1989
[24] A Alekseevsky and D Alekseevsky ldquoG-manifold with one-dimensional orbit spacerdquo Advances in Soviet Mathematics vol8 pp 1ndash31 1992
[25] A Besse Einstein Manifolds Springer Berlin Germany 1987[26] R L Bryant ldquoMetrics with holonomy 119866
2or spin (7)rdquo in Arbeit-
stagung Bonn 1984 vol 1111 of Lecture Notes in Mathematics pp269ndash277 Springer Berlin Germany 1985
[27] R L Bryant ldquoA survey of Riemannian metrics with specialholonomy groupsrdquo in Proceedings of the International Congressof Mathematicians vol 1 pp 505ndash514 AMS Berkeley CalifUSA 1987
[28] R L Bryant ldquoMetrics with exceptional holonomyrdquo Annals ofMathematics Second Series vol 126 no 3 pp 525ndash576 1987
[29] R Bryant and F Harvery ldquoSome remarks on the geometry ofmanifolds with exceptional holonomyrdquo preprint 1994
[30] R L Bryant and S M Salamon ldquoOn the construction ofsome complete metrics with exceptional holonomyrdquo DukeMathematical Journal vol 58 no 3 pp 829ndash850 1989
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Differential EquationsInternational Journal of
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Operations ResearchAdvances in
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Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
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Algebra
Discrete Dynamics in Nature and Society
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Decision SciencesAdvances in
Discrete MathematicsJournal of
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Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
2 Advances in Mathematical Physics
In Section 3 this manifold is proved to be simply connectedbut not complete hence not isometric to the hyperbolic spaceHowever it is proved to be a cohomogeneity one manifoldby Theorem 14 In Section 4 several tricks are used basedon some special properties to get geodesics and the Jacobivector fields The geodesics are the sets of fixed points ofisometric transformations which include symmetries to linesparalleled to 119910-axis Meanwhile the Jacobi vector fields arecalculated Then the instability of the geodesic spreads isanalyzed via the behaviors of the the Jacobi vector field
Remark 1 It is well known that the upper plane R2+admits a
hyperbolic metric 119892119867with constant negative curvature That
is
119892119867
=
[[[
[
1
11991020
01
1199102
]]]
]
(2)
However in this paper we give another metric on R2+
with constant negative curvature but not isometric to thehyperbolic space
2 Geometric Structures of the WCED Model
From the theory of information geometry one can definean 119898-dimensional statistical manifold 119872 over unit sphereswhich is a set of probability densities namely
119872 = 119901 (119909 120579) (3)
The parameter 120579 = (1205791
1205792
120579119898
) plays the role of coordi-nate systems The Fisher information matrix 119892 acting as aRiemannian metric is then given by the expectation
(119892119894119895) = (119864 [(120597
119894119897) (120597119895119897)]) (4)
where 119897(119909 120579) = ln119901(119909 120579) and 120597119894
= 120597120597120579119894 On a statistical
manifold the Riemannian connection coefficient Γ119894119895119896
is (seeeg [1 2 19ndash21])
Γ119894119895119896
= 119864 [(120597119894120597119895119897) (120597119896119897)] +
1 minus 120572
2119864 [(120597119894119897) (120597119895119897) (120597119896119897)] (5)
which can be expressed as a classical formula Γ119894119895119896
=
(12)(120597119894119892119895119896
+ 120597119895119892119896119894
minus 120597119896119892119894119895) equivalently
If (1205791
1205792
120579119898
) is a local coordinate of 119872 then forany vector field 119883 on 119872 one has 119883 = 119883
119894
120597119894 where 119883
119894
are smooth functions with respect to (1205791
1205792
120579119898
) TheEinstein summation convention is used here and all throughthe paper With the Riemannian connection the curvaturetensor is defined by [19 20]
119877 (119883 119884) 119885 = nabla119883
nabla119884119885 minus nabla
119884nabla119883
119885 minus nabla[119883119884]
119885 (6)
and the Riemannian curvature tensor is
119877 (119883 119884 119885 119882) = 119892 (119877 (119885 119882) 119883 119884) (7)
where 119883 119884 119885 119882 are smooth vector fields on 119872 and [sdot sdot]
represents the Lie bracket namely [119883 119884] = 119883 ∘ 119884 minus 119884 ∘ 119883The local representation of the curvature tensor satisfies
119877119898119895119896119897
= (120597119898
Γ119905
119895119896minus 120597119895Γ119905
119898119896) 119892119905119897
+ (Γ119898119905119897
Γ119905
119895119896minus Γ119895119905119897
Γ119905
119898119896) (8)
where Γ119896
119898119895= Γ119898119895119905
119892119905119896 and (119892
119905119896
) is the inverse of the metricmatrix (119892
119905119896)
The Ricci curvature and the sectional curvature aredefined by
119877119898119896
= 119877119898119895119897119896
119892119895119897
(9)
119870119894119895
= minus
119877119894119895119894119895
119892119894119894119892119895119895
minus 1198922
119894119895
(10)
respectivelyA curve 120585(119905) on 119872 is said to be a geodesic if its tangent
vector 120585(119905) is displaced parallel along the curve 120585(119905) that is
nabla 120585(119905)
120585 (119905) = 0 (11)
and it has the following local form
d2120579119896
d1199052+ Γ119896
119895119898
d120579119895
d119905
d120579119898
d119905= 0 (12)
Suppose that the solution of (12) is 120579(119905 120573) where 120573 is a vectorwhose components are the integration constants
Considering the wrapped Cauchy entropic dynamicalmodel the corresponding statistical manifold is
119878 = 119901 (119909 120579) | 120579 = (1205791
1205792
) isin R2
+ (13)
where 119901(119909 120579) is given by (1) with parameters 1205791
= 120583 and 1205792
=
120574 The Fisher information matrix can be easily calculated as
119892 = diag (1
2sinh21205792
1
2sinh21205792) (14)
Proposition 2 Thenonzero components of the Ricci curvatureare
11987711
= 11987722
= minus1
sinh21205792 (15)
Proof A direct calculation of (5) gives the nonvanishingRiemannian connection coefficients
Γ112
= minusΓ121
= minusΓ211
= minusΓ222
=cosh 120579
2
2sinh31205792 (16)
From the relation Γ119896
119898119895= Γ119898119895119905
119892119905119896 one can get another type of
connection coefficients
Γ2
11= minusΓ1
12= minusΓ1
21= minusΓ2
22=cosh 120579
2
sinh 1205792 (17)
From (8) the following nonzero component of the curvaturetensor is obtained
1198771212
=1
2sinh41205792 (18)
Therefore the proof can be finished by a simple substitutionof (18) into (9)
Advances in Mathematical Physics 3
The following theorem is obtained by substituting (18)and (14) into (10)
Theorem 3 119878 is a manifold with constant negative curvature119870 = minus2
3 Topological and Geometric Properties of 119878
Lemma 4 119878 is diffeomorphic to R2+and hence simply con-
nected
Proof The topology as well as the smooth structure of 119878 isinduced by those onR2
+ hence 119878 is diffeomorphic toR2
+ The
fact that R2+is simply connected implies that 119878 is also simply
connected
If 119878 were also complete it would be a space formwith constant negative curvature which was isometric tothe hyperbolic space 119867
2
(minus2) However 119878 is not completeWe begin with a necessary and sufficient condition of thecompleteness
Definition 5 (see [19]) Let (119872 119892) be a RiemannianmanifoldA smooth curve 120574 [0 +infin) rarr 119872 is called a divergent curveif for any compact subset 119870 sub 119872 there exists 119905
0gt 0 st
120574(1199050) notin 119870 If 120574 is a divergent curve its length is defined by
119871 (120574) = lim119904rarr+infin
int
119904
0
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905 (19)
Lemma 6 (see [22]) (119872 119892 119889) is a connected Riemannianmanifold then 119872 is complete if and only if every divergentcurve has infinite length
Proof (1) Suppose that 119872 is complete and 120574 is a divergentcurve Consider
119881119899
= 119901 isin 119872 | 119889 (119901 120574 (0)) le 119899 forall119899 isin N (20)
where for each 119899 119881119899is bounded and closed hence compact
The divergence of 120574 implies that for all 119899 isin Nlowast exist119905119899
ge 0 st120574(119905119899) notin 119881119899 As a result
int
119905119899
0
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905 ge 119889 (120574 (0) 120574 (119905
119899)) ge 119899 (21)
hence 119871(120574) = +infin(2) Suppose every divergent curve has infinite length
Assume that 119872 is noncomplete which implies that exist119901 isin 119872existV0
isin 119879119901119872 and 120574(119905) = exp
119901(119905V0) is only defined on 119905 isin [0 1)
119871(120574) lt |V0| lt +infin means 120574 is not divergent that is there
exists a compact subset 119870 sub 119872 st 120574(119905) isin 119870 for all 119905 Choosesequence 119905
119899+infin
119899=1 st 119905
119899rarr 1 and 119905
119899lt 119905119899+1
for all 119899 isin N It isobvious that 119889(120574(119905
119899) 120574(119905119898
)) rarr 0 when 119899 119898 are sufficientlylarge Hence 120574(119905
119899) is a Cauchy sequence The completeness
of 119872 implies that there exists 119902 isin 119870 st 120574(119905119899) rarr 119902
Then 120574(1) = 119902 is a extension of 120574 from [0 1) to [0 1]
which contradicts to the assumption which implies that119872 isin fact complete
Theorem 7 119878 is noncomplete
Proof Suppose that 120574(119905) = (0 119905) isin R2+ 119905 isin [1 +infin) is a curve
along the 119910-axis It is obvious that 120574 is divergent Howeverthe length of 120574 satisfies
119871 (120574) = int
+infin
1
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905
= int
+infin
1
1
radic2 sinh (119905)
d119905
=1
radic2
ln(tanh(119905
2))
1003816100381610038161003816100381610038161003816
+infin
1
=ln (119890 + 1) minus ln (119890 minus 1)
radic2
lt +infin
(22)
This implies 119878 is noncomplete by Lemma 6
Although 119878 is neither isometric to the hyperbolic spacenor a symmetric space it is ldquopartly symmetricrdquo which ispresented in Lemma 10
Definition 8 Let 119868(119878) be the group of isometric transforma-tions on 119878 A family of transformations on 119878 are defined as
120593120572
119878 997888rarr 119878 (1205791
1205792
) 997891997888rarr (2120572 minus 1205791
1205792
) forall120572 isin R
(23)
Remark 9 120593120572is just the reflection about the line 120579
1
= 120572which is a line parallel to the 119910-axis
Lemma 10 120593120572
isin 119868(119878) for all 120572 isin R
Proof For any fixed 120572 isin R for all 119901 = (1205791
1205792
) isin 119878 119902 =
120593120572(119901) = (2120572 minus 120579
1
1205792
)Consider
1205741
(119905) = (1205791
+ 119905 1205792
) 1205742
(119905) = (1205791
1205792
+ 119905)
(120593120572)lowast119901
(120597
1205971205791) =
dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(120593120572
∘ 1205741
(119905))
=dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(2120572 minus 1205791
minus 119905 1205792
) = minus120597
1205971205791
10038161003816100381610038161003816100381610038161003816119902
(120593120572)lowast119901
(120597
1205971205792) =
dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(120593120572
∘ 1205742
(119905))
=dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(2120572 minus 1205791
1205792
+ 119905) =120597
1205971205792
10038161003816100381610038161003816100381610038161003816119902
119892119902
((120593120572)lowast119901
(120597
1205971205791) (120593120572)lowast119901
(120597
1205971205791))
= 119892119902
(minus120597
1205971205791 minus
120597
1205971205791) =
1
2sinh21205792= 119892119901
(120597
1205971205791
120597
1205971205791)
4 Advances in Mathematical Physics
119892119902
((120593120572)lowast119901
(120597
1205971205791) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(minus120597
1205971205791
120597
1205971205792) = 0 = 119892
119901(
120597
1205971205791
120597
1205971205792)
119892119902
((120593120572)lowast119901
(120597
1205971205792) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(120597
1205971205792
120597
1205971205792) =
1
2sinh21205792= 119892119901
(120597
1205971205792
120597
1205971205792)
(24)
Hence 120593120572is an isometry
As a result 119866 = 120593120572
| 120572 isin R is a subgroup of 119868(119878)Lemma 10 implies that 119878 is ldquoalmostrdquo homogeneous althoughnot truly homogeneous In fact 119878 is a cohomogeneity onemanifold defined in Definition 11
Definition 11 Let (119872 119892) be a Riemannianmanifold and 119868(119872)
is its group of isometric transformations Then 119868(119872) has anatural action Φ on 119872
Φ 119868 (119872) times 119872 997888rarr 119872 (120593 119901) 997891997888rarr 120593 (119901)
forall120593 isin 119868 (119872) 119901 isin 119872
(25)
119872 is a cohomogeneity one manifold if the codimension oforbit space of this action is 1
Remark 12 The codimension of the orbit space is closelyrelated to the homogeneous properties For example if 119872 isa homogeneous space then the orbit space is whole manifold119872 and hence its codimension is 0The less that codimensionis the more homogeneous the manifold is In other wordsa cohomogeneity one manifold is ldquothe most homogeneousmanifoldrdquo except for the real ones
Actually cohomogeneity one manifolds are natural gen-eralizations of homogeneousmanifoldsThe systematic studyof cohomogeneity onemanifolds was started by Bergery whosuccessfully constructed new invariant Einstein metrics oncohomogeneity one manifolds In addition Bryant and Sala-mon constructed special metrics with exceptional holonomygroups 119866
2and Spin(7) on these manifolds [23ndash30]
We state a well known result without proof beforeTheorem 14
Lemma 13 Every homogeneous space is complete
Theorem 14 119878 is a cohomogeneity one manifold
Proof Let 119901 = (1205791
1205792
) isin 119878 and 119868(119878)119901
= 120593(119901) | 120593 isin 119868(119878)
be its orbit space If dim(119868(119878)119901) = 2 119878 will be homogeneous
Lemma 13 implies that 119878 is complete which contradicts toTheorem 7 This contradiction implies dim(119868(119878)
119901) le 1
On the other hand
119866119901
= 120593 (119901) | 120593 isin 119866 = 120593120572
(119901) | 120572 isin R
= (2120572 minus 1205791
1205792
) | 120572 isin R = (119909 1205792
) | 119909 isin R
(26)
Since 119866 is a subgroup of 119868(119878) 119866119901
sub 119868(119878)119901 This implies that
dim (119868 (119878)119901) ge dim (119866
119901) = 1 (27)
Based on the two inequalities we conclude that dim(119868(119878)119901) =
1 hence its codimension is 1 which means that 119878 is acohomogeneity one manifold
4 Instability Analysis
In this section we will calculate some geodesics and investi-gate the instability of the geodesics by the Jacobi vector fields
Combining (12) and (17) the geodesic equations of theWCED model are given by the following differential system
d21205791
d1199052minus
2 cosh 1205792
sinh 1205792
d1205791
d119905
d1205792
d119905= 0
d21205792
d1199052+cosh 120579
2
sinh 1205792(d1205791
d119905)
2
minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(28)
Generally these equations are quite hard to be solvedhowever we can get some special geodesics based on thecohomogeneity one property
Lemma 15 All lines parallel to the y-axis are geodesics
Proof It is well known that the fixed-points set of anyisometry is a geodesic Since 120593
120572is an isometry and its fixed-
points set is the line 119909 = 1205791 the lemma follows
According to Lemma 15 the equation of such geodesicsatisfies
1205791
= 1205791
0 (29)
Hence (28) can be reduced to
d1205791
d119905= 0
d21205792
d1199052minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(30)
Then solution is expressed as
1205791
= 1198863
1205792
= ln100381610038161003816100381610038161003816100381610038161003816
1198862exp 119886
1119905 + 1
1198862exp 119886
1119905 minus 1
100381610038161003816100381610038161003816100381610038161003816
(31)
Consider the parameter family of geodesics
F (119862) = 120579119897
(119905 119862)119897=12
(32)
where 120579119897 is a geodesic satisfying (28) and 119862 is an integration
constant vectorThe length of geodesics inF(119862) is defined as
Θ (119905 120573) = int (119892119894119895d120579119894d120579119895
)12
(33)
Advances in Mathematical Physics 5
Therefore the length of geodesics on WCED model isobtained as
Θ (119905 119862) = int
119905
0
radic11989211
(d1205791
d119905)
2
+ 11989222
(d1205792
d119905)
2
d120591 =radic21198621
2119905
(34)
where 1198621is constant In order to investigate the behavior of
two neighboring geodesics labeled by the parameter 1198621 we
consider the following difference
ΔΘ = (
radic2 (1198621
+ 1205751198621)
2minus
radic21198621
2) 119905 (35)
It is clear that ΔΘ diverges that is the length of twoneighboring geodesics with slightly different parameters 119862
1
and 1198621
+ 1205751198621differs in a remarkable way as 119905 rarr infin
The stability of the geodesics is completely determinedby the curvature of manifold Studying the stability ofdynamics means determining the evolution of perturbationsof geodesics For isotropic manifolds the geodesic spreadis unstable only if their constant sectional curvatures arenegative As long as the curvatures are negative the geodesicspread is unstable even if the manifold is no longer isotropic[19] However it is more attractive to know the divergentdegree of a geodesic
The Jacobi vector field 119869 that is the evolution perturba-tion vector satisfies the following (Jacobi) equation
nabla 120585(119905)
nabla 120585(119905)
119869 = 119877 ( 120585 (119905) 119869) 120585 (119905) (36)
where 120585(119905) is a geodesic on manifold 119872 It is also called thegeodesic derivation equation as it has close connections withthe geodesic In general the Jacobi equations are difficult tosolve but in particular this manifold has a constant negativecurvature which is of great help Given a normal geodesic 120585
and supposing 119869 is a normal Jacobi vector field along 120585(119905) then
119877 ( 120585 (119905) 119869) 120585 (119905) = 2 (119892 ( 120585 (119905) 120585 (119905)) 119869 minus 119892 ( 120585 (119905) 119869) 120585 (119905))
= 2119869
(37)
Thus the Jacobi equation is reduced to
d2119869 (119905)
d1199052minus 2119869 (119905) = 0 (38)
Choose a unit orthogonal frame 119890119894(119905) st 119890
2(119905) = 120585(119905) and
suppose
119869 (119905) = 119869119894
(119905) 119890119894(119905) (39)
Then the Jacobi equation satisfies
d21198691 (119905)d1199052
minus 21198691
(119905) = 0
1198692
(119905) = 0
(40)
The solutions are
1198691
(119905) = 1198621119890radic2119905
+ 1198622119890minusradic2119905
1198692
(119905) = 0
(41)
This means that the geodesic spread onmanifold is describedby means of an exponential order divergent Jacobi vectorfield
5 Conclusion and Remarks
In this paper we investigate the manifold of wrapped Cauchydistributions By considering the geometric structures of theWCED we conclude that the WCED is a constant negativecurvature space with119870 = minus2 By a series of lemmas and theo-rems we prove that it is a cohomogeneity one manifold Thisexample is interesting because of its statistical backgroundwhile some other examples are deliberately constructed Inaddition we calculate the geodesics and the Jacobi vector fieldby some tricks based on some special properties of 119878 As aresult the divergent behavior of geodesics can be describedas an exponential order divergent Jacobi vector field
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Authorsrsquo Contribution
The authors declare that the study was realized in collab-oration with the same responsibility All authors read andapproved the final paper
Acknowledgments
This work is supported by the National Natural ScienceFoundations of China (nos 11126161 and NSFC61440058)Beijing Higher Education Young Elite Teacher Project (noYETP 0388) and the Fundamental Research Funds for theCentral Universities (no FRF-BR-12-005)
References
[1] S Amari Differential Geometrical Methods in StatisticsSpringer Berlin Germany 1990
[2] S Amari and H Nagaoka Methods of Information Geo metryOxford University Press Oxford UK 2000
[3] T Li L Peng and H Sun ldquoThe geometric structure of theinverse gamma distributionrdquo Beitrage zur Algebra und Geome-trie vol 49 no 1 pp 217ndash225 2008
[4] L Peng H Sun D Sun and J Yi ldquoThe geometric structuresand instability of entropic dynamical modelsrdquo Advances inMathematics vol 227 no 1 pp 459ndash471 2011
[5] L Peng H Sun and G Xu ldquoInformation geometric charac-terization of the complexity of fractional Brownian motionsrdquoJournal of Mathematical Physics vol 53 no 12 Article ID123305 12 pages 2012
6 Advances in Mathematical Physics
[6] L Peng H Sun and X Sun ldquoGeometric structure of Hamilto-nian dynamics with conformal Eisenhart metricrdquo InternationalJournal of Mathematics and Mathematical Sciences vol 2011Article ID 710274 26 pages 2011
[7] A Caticha ldquoEntropic dynamicsrdquo in Bayesian Inference andMaximum Entropy Methods in Science and Engineering R LFry Ed AIP Conference Proceedings pp 617ndash302 2002
[8] C Cafaro and S A Ali ldquoJacobi fields on statistical manifolds ofnegative curvaturerdquo Physica D Nonlinear Phenomena vol 234no 1 pp 70ndash80 2007
[9] K V Mardia and P E Jupp Directional Statistics JohnWiley ampSons New York NY USA 1999
[10] C Bingham ldquoAn antipodally symmetric distribution on thesphererdquoThe Annals of Statistics vol 2 pp 1201ndash1225 1974
[11] J T Kent ldquoThe Fisher-Bingham distribution on the sphererdquoJournal of the Royal Statistical Society vol 44 pp 71ndash80 1982
[12] R A Fisher ldquoDispersion on a sphererdquo Proceedings of the RoyalSociety of London A vol 217 pp 295ndash305 1953
[13] N I Fisher Statistical Analysis of Circular Data CambridgeUniversity Press Cambridge UK 1996
[14] G Borradaile Statistics of Earth Science Data Springer NewYork NY USA 2003
[15] K A Keating and S Cherry ldquoModeling utilization distributionsin space and timerdquo Ecology vol 90 no 7 pp 1971ndash1980 2009
[16] H-I Wu B-L Li T A Springer and W H Neill ldquoModellinganimal movement as a persistent random walk in two dimen-sions expected magnitude of net displacementrdquo EcologicalModelling vol 132 no 1-2 pp 115ndash124 2000
[17] Y Vermard E Rivot S Mahevas P Marchal and D GascuelldquoIdentifying fishing trip behaviour and estimating fishing effortfrom VMS data using Bayesian Hidden Markov ModelsrdquoEcological Modelling vol 221 no 15 pp 1757ndash1769 2010
[18] K Thorup J Raboslashl and J J Madsen ldquoCan clock-and-compassexplain the distribution of ringing recoveries of pied flycatch-ersrdquo Animal Behaviour vol 60 no 2 pp F3ndashF8 2000
[19] M P do Carmo Riemannian Geometry Birkhauser BostonMass USA 1992
[20] P Petersen Riemannian Geometry Springer New York NYUSA 2nd edition 2006
[21] C R Rao ldquoInformation and the accuracy attainable in theestimation of statistical parametersrdquo Bulletin of the CalcuttaMathematical Society vol 37 pp 81ndash91 1945
[22] W Chen and X Li Introduction to Riemannian GeometryPeking University Press Beijing China 2012
[23] D Alekseevsky ldquoRiemannian manifolds of cohomogeneityonerdquo in Proceedings of the Colloquium on Differential Geometryvol 56 of Colloeq Math Soc J Bolyai pp 9ndash22 1989
[24] A Alekseevsky and D Alekseevsky ldquoG-manifold with one-dimensional orbit spacerdquo Advances in Soviet Mathematics vol8 pp 1ndash31 1992
[25] A Besse Einstein Manifolds Springer Berlin Germany 1987[26] R L Bryant ldquoMetrics with holonomy 119866
2or spin (7)rdquo in Arbeit-
stagung Bonn 1984 vol 1111 of Lecture Notes in Mathematics pp269ndash277 Springer Berlin Germany 1985
[27] R L Bryant ldquoA survey of Riemannian metrics with specialholonomy groupsrdquo in Proceedings of the International Congressof Mathematicians vol 1 pp 505ndash514 AMS Berkeley CalifUSA 1987
[28] R L Bryant ldquoMetrics with exceptional holonomyrdquo Annals ofMathematics Second Series vol 126 no 3 pp 525ndash576 1987
[29] R Bryant and F Harvery ldquoSome remarks on the geometry ofmanifolds with exceptional holonomyrdquo preprint 1994
[30] R L Bryant and S M Salamon ldquoOn the construction ofsome complete metrics with exceptional holonomyrdquo DukeMathematical Journal vol 58 no 3 pp 829ndash850 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Advances in Mathematical Physics 3
The following theorem is obtained by substituting (18)and (14) into (10)
Theorem 3 119878 is a manifold with constant negative curvature119870 = minus2
3 Topological and Geometric Properties of 119878
Lemma 4 119878 is diffeomorphic to R2+and hence simply con-
nected
Proof The topology as well as the smooth structure of 119878 isinduced by those onR2
+ hence 119878 is diffeomorphic toR2
+ The
fact that R2+is simply connected implies that 119878 is also simply
connected
If 119878 were also complete it would be a space formwith constant negative curvature which was isometric tothe hyperbolic space 119867
2
(minus2) However 119878 is not completeWe begin with a necessary and sufficient condition of thecompleteness
Definition 5 (see [19]) Let (119872 119892) be a RiemannianmanifoldA smooth curve 120574 [0 +infin) rarr 119872 is called a divergent curveif for any compact subset 119870 sub 119872 there exists 119905
0gt 0 st
120574(1199050) notin 119870 If 120574 is a divergent curve its length is defined by
119871 (120574) = lim119904rarr+infin
int
119904
0
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905 (19)
Lemma 6 (see [22]) (119872 119892 119889) is a connected Riemannianmanifold then 119872 is complete if and only if every divergentcurve has infinite length
Proof (1) Suppose that 119872 is complete and 120574 is a divergentcurve Consider
119881119899
= 119901 isin 119872 | 119889 (119901 120574 (0)) le 119899 forall119899 isin N (20)
where for each 119899 119881119899is bounded and closed hence compact
The divergence of 120574 implies that for all 119899 isin Nlowast exist119905119899
ge 0 st120574(119905119899) notin 119881119899 As a result
int
119905119899
0
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905 ge 119889 (120574 (0) 120574 (119905
119899)) ge 119899 (21)
hence 119871(120574) = +infin(2) Suppose every divergent curve has infinite length
Assume that 119872 is noncomplete which implies that exist119901 isin 119872existV0
isin 119879119901119872 and 120574(119905) = exp
119901(119905V0) is only defined on 119905 isin [0 1)
119871(120574) lt |V0| lt +infin means 120574 is not divergent that is there
exists a compact subset 119870 sub 119872 st 120574(119905) isin 119870 for all 119905 Choosesequence 119905
119899+infin
119899=1 st 119905
119899rarr 1 and 119905
119899lt 119905119899+1
for all 119899 isin N It isobvious that 119889(120574(119905
119899) 120574(119905119898
)) rarr 0 when 119899 119898 are sufficientlylarge Hence 120574(119905
119899) is a Cauchy sequence The completeness
of 119872 implies that there exists 119902 isin 119870 st 120574(119905119899) rarr 119902
Then 120574(1) = 119902 is a extension of 120574 from [0 1) to [0 1]
which contradicts to the assumption which implies that119872 isin fact complete
Theorem 7 119878 is noncomplete
Proof Suppose that 120574(119905) = (0 119905) isin R2+ 119905 isin [1 +infin) is a curve
along the 119910-axis It is obvious that 120574 is divergent Howeverthe length of 120574 satisfies
119871 (120574) = int
+infin
1
100381610038161003816100381610038161205741015840
(119905)10038161003816100381610038161003816d119905
= int
+infin
1
1
radic2 sinh (119905)
d119905
=1
radic2
ln(tanh(119905
2))
1003816100381610038161003816100381610038161003816
+infin
1
=ln (119890 + 1) minus ln (119890 minus 1)
radic2
lt +infin
(22)
This implies 119878 is noncomplete by Lemma 6
Although 119878 is neither isometric to the hyperbolic spacenor a symmetric space it is ldquopartly symmetricrdquo which ispresented in Lemma 10
Definition 8 Let 119868(119878) be the group of isometric transforma-tions on 119878 A family of transformations on 119878 are defined as
120593120572
119878 997888rarr 119878 (1205791
1205792
) 997891997888rarr (2120572 minus 1205791
1205792
) forall120572 isin R
(23)
Remark 9 120593120572is just the reflection about the line 120579
1
= 120572which is a line parallel to the 119910-axis
Lemma 10 120593120572
isin 119868(119878) for all 120572 isin R
Proof For any fixed 120572 isin R for all 119901 = (1205791
1205792
) isin 119878 119902 =
120593120572(119901) = (2120572 minus 120579
1
1205792
)Consider
1205741
(119905) = (1205791
+ 119905 1205792
) 1205742
(119905) = (1205791
1205792
+ 119905)
(120593120572)lowast119901
(120597
1205971205791) =
dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(120593120572
∘ 1205741
(119905))
=dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(2120572 minus 1205791
minus 119905 1205792
) = minus120597
1205971205791
10038161003816100381610038161003816100381610038161003816119902
(120593120572)lowast119901
(120597
1205971205792) =
dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(120593120572
∘ 1205742
(119905))
=dd119905
10038161003816100381610038161003816100381610038161003816119905=0
(2120572 minus 1205791
1205792
+ 119905) =120597
1205971205792
10038161003816100381610038161003816100381610038161003816119902
119892119902
((120593120572)lowast119901
(120597
1205971205791) (120593120572)lowast119901
(120597
1205971205791))
= 119892119902
(minus120597
1205971205791 minus
120597
1205971205791) =
1
2sinh21205792= 119892119901
(120597
1205971205791
120597
1205971205791)
4 Advances in Mathematical Physics
119892119902
((120593120572)lowast119901
(120597
1205971205791) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(minus120597
1205971205791
120597
1205971205792) = 0 = 119892
119901(
120597
1205971205791
120597
1205971205792)
119892119902
((120593120572)lowast119901
(120597
1205971205792) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(120597
1205971205792
120597
1205971205792) =
1
2sinh21205792= 119892119901
(120597
1205971205792
120597
1205971205792)
(24)
Hence 120593120572is an isometry
As a result 119866 = 120593120572
| 120572 isin R is a subgroup of 119868(119878)Lemma 10 implies that 119878 is ldquoalmostrdquo homogeneous althoughnot truly homogeneous In fact 119878 is a cohomogeneity onemanifold defined in Definition 11
Definition 11 Let (119872 119892) be a Riemannianmanifold and 119868(119872)
is its group of isometric transformations Then 119868(119872) has anatural action Φ on 119872
Φ 119868 (119872) times 119872 997888rarr 119872 (120593 119901) 997891997888rarr 120593 (119901)
forall120593 isin 119868 (119872) 119901 isin 119872
(25)
119872 is a cohomogeneity one manifold if the codimension oforbit space of this action is 1
Remark 12 The codimension of the orbit space is closelyrelated to the homogeneous properties For example if 119872 isa homogeneous space then the orbit space is whole manifold119872 and hence its codimension is 0The less that codimensionis the more homogeneous the manifold is In other wordsa cohomogeneity one manifold is ldquothe most homogeneousmanifoldrdquo except for the real ones
Actually cohomogeneity one manifolds are natural gen-eralizations of homogeneousmanifoldsThe systematic studyof cohomogeneity onemanifolds was started by Bergery whosuccessfully constructed new invariant Einstein metrics oncohomogeneity one manifolds In addition Bryant and Sala-mon constructed special metrics with exceptional holonomygroups 119866
2and Spin(7) on these manifolds [23ndash30]
We state a well known result without proof beforeTheorem 14
Lemma 13 Every homogeneous space is complete
Theorem 14 119878 is a cohomogeneity one manifold
Proof Let 119901 = (1205791
1205792
) isin 119878 and 119868(119878)119901
= 120593(119901) | 120593 isin 119868(119878)
be its orbit space If dim(119868(119878)119901) = 2 119878 will be homogeneous
Lemma 13 implies that 119878 is complete which contradicts toTheorem 7 This contradiction implies dim(119868(119878)
119901) le 1
On the other hand
119866119901
= 120593 (119901) | 120593 isin 119866 = 120593120572
(119901) | 120572 isin R
= (2120572 minus 1205791
1205792
) | 120572 isin R = (119909 1205792
) | 119909 isin R
(26)
Since 119866 is a subgroup of 119868(119878) 119866119901
sub 119868(119878)119901 This implies that
dim (119868 (119878)119901) ge dim (119866
119901) = 1 (27)
Based on the two inequalities we conclude that dim(119868(119878)119901) =
1 hence its codimension is 1 which means that 119878 is acohomogeneity one manifold
4 Instability Analysis
In this section we will calculate some geodesics and investi-gate the instability of the geodesics by the Jacobi vector fields
Combining (12) and (17) the geodesic equations of theWCED model are given by the following differential system
d21205791
d1199052minus
2 cosh 1205792
sinh 1205792
d1205791
d119905
d1205792
d119905= 0
d21205792
d1199052+cosh 120579
2
sinh 1205792(d1205791
d119905)
2
minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(28)
Generally these equations are quite hard to be solvedhowever we can get some special geodesics based on thecohomogeneity one property
Lemma 15 All lines parallel to the y-axis are geodesics
Proof It is well known that the fixed-points set of anyisometry is a geodesic Since 120593
120572is an isometry and its fixed-
points set is the line 119909 = 1205791 the lemma follows
According to Lemma 15 the equation of such geodesicsatisfies
1205791
= 1205791
0 (29)
Hence (28) can be reduced to
d1205791
d119905= 0
d21205792
d1199052minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(30)
Then solution is expressed as
1205791
= 1198863
1205792
= ln100381610038161003816100381610038161003816100381610038161003816
1198862exp 119886
1119905 + 1
1198862exp 119886
1119905 minus 1
100381610038161003816100381610038161003816100381610038161003816
(31)
Consider the parameter family of geodesics
F (119862) = 120579119897
(119905 119862)119897=12
(32)
where 120579119897 is a geodesic satisfying (28) and 119862 is an integration
constant vectorThe length of geodesics inF(119862) is defined as
Θ (119905 120573) = int (119892119894119895d120579119894d120579119895
)12
(33)
Advances in Mathematical Physics 5
Therefore the length of geodesics on WCED model isobtained as
Θ (119905 119862) = int
119905
0
radic11989211
(d1205791
d119905)
2
+ 11989222
(d1205792
d119905)
2
d120591 =radic21198621
2119905
(34)
where 1198621is constant In order to investigate the behavior of
two neighboring geodesics labeled by the parameter 1198621 we
consider the following difference
ΔΘ = (
radic2 (1198621
+ 1205751198621)
2minus
radic21198621
2) 119905 (35)
It is clear that ΔΘ diverges that is the length of twoneighboring geodesics with slightly different parameters 119862
1
and 1198621
+ 1205751198621differs in a remarkable way as 119905 rarr infin
The stability of the geodesics is completely determinedby the curvature of manifold Studying the stability ofdynamics means determining the evolution of perturbationsof geodesics For isotropic manifolds the geodesic spreadis unstable only if their constant sectional curvatures arenegative As long as the curvatures are negative the geodesicspread is unstable even if the manifold is no longer isotropic[19] However it is more attractive to know the divergentdegree of a geodesic
The Jacobi vector field 119869 that is the evolution perturba-tion vector satisfies the following (Jacobi) equation
nabla 120585(119905)
nabla 120585(119905)
119869 = 119877 ( 120585 (119905) 119869) 120585 (119905) (36)
where 120585(119905) is a geodesic on manifold 119872 It is also called thegeodesic derivation equation as it has close connections withthe geodesic In general the Jacobi equations are difficult tosolve but in particular this manifold has a constant negativecurvature which is of great help Given a normal geodesic 120585
and supposing 119869 is a normal Jacobi vector field along 120585(119905) then
119877 ( 120585 (119905) 119869) 120585 (119905) = 2 (119892 ( 120585 (119905) 120585 (119905)) 119869 minus 119892 ( 120585 (119905) 119869) 120585 (119905))
= 2119869
(37)
Thus the Jacobi equation is reduced to
d2119869 (119905)
d1199052minus 2119869 (119905) = 0 (38)
Choose a unit orthogonal frame 119890119894(119905) st 119890
2(119905) = 120585(119905) and
suppose
119869 (119905) = 119869119894
(119905) 119890119894(119905) (39)
Then the Jacobi equation satisfies
d21198691 (119905)d1199052
minus 21198691
(119905) = 0
1198692
(119905) = 0
(40)
The solutions are
1198691
(119905) = 1198621119890radic2119905
+ 1198622119890minusradic2119905
1198692
(119905) = 0
(41)
This means that the geodesic spread onmanifold is describedby means of an exponential order divergent Jacobi vectorfield
5 Conclusion and Remarks
In this paper we investigate the manifold of wrapped Cauchydistributions By considering the geometric structures of theWCED we conclude that the WCED is a constant negativecurvature space with119870 = minus2 By a series of lemmas and theo-rems we prove that it is a cohomogeneity one manifold Thisexample is interesting because of its statistical backgroundwhile some other examples are deliberately constructed Inaddition we calculate the geodesics and the Jacobi vector fieldby some tricks based on some special properties of 119878 As aresult the divergent behavior of geodesics can be describedas an exponential order divergent Jacobi vector field
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Authorsrsquo Contribution
The authors declare that the study was realized in collab-oration with the same responsibility All authors read andapproved the final paper
Acknowledgments
This work is supported by the National Natural ScienceFoundations of China (nos 11126161 and NSFC61440058)Beijing Higher Education Young Elite Teacher Project (noYETP 0388) and the Fundamental Research Funds for theCentral Universities (no FRF-BR-12-005)
References
[1] S Amari Differential Geometrical Methods in StatisticsSpringer Berlin Germany 1990
[2] S Amari and H Nagaoka Methods of Information Geo metryOxford University Press Oxford UK 2000
[3] T Li L Peng and H Sun ldquoThe geometric structure of theinverse gamma distributionrdquo Beitrage zur Algebra und Geome-trie vol 49 no 1 pp 217ndash225 2008
[4] L Peng H Sun D Sun and J Yi ldquoThe geometric structuresand instability of entropic dynamical modelsrdquo Advances inMathematics vol 227 no 1 pp 459ndash471 2011
[5] L Peng H Sun and G Xu ldquoInformation geometric charac-terization of the complexity of fractional Brownian motionsrdquoJournal of Mathematical Physics vol 53 no 12 Article ID123305 12 pages 2012
6 Advances in Mathematical Physics
[6] L Peng H Sun and X Sun ldquoGeometric structure of Hamilto-nian dynamics with conformal Eisenhart metricrdquo InternationalJournal of Mathematics and Mathematical Sciences vol 2011Article ID 710274 26 pages 2011
[7] A Caticha ldquoEntropic dynamicsrdquo in Bayesian Inference andMaximum Entropy Methods in Science and Engineering R LFry Ed AIP Conference Proceedings pp 617ndash302 2002
[8] C Cafaro and S A Ali ldquoJacobi fields on statistical manifolds ofnegative curvaturerdquo Physica D Nonlinear Phenomena vol 234no 1 pp 70ndash80 2007
[9] K V Mardia and P E Jupp Directional Statistics JohnWiley ampSons New York NY USA 1999
[10] C Bingham ldquoAn antipodally symmetric distribution on thesphererdquoThe Annals of Statistics vol 2 pp 1201ndash1225 1974
[11] J T Kent ldquoThe Fisher-Bingham distribution on the sphererdquoJournal of the Royal Statistical Society vol 44 pp 71ndash80 1982
[12] R A Fisher ldquoDispersion on a sphererdquo Proceedings of the RoyalSociety of London A vol 217 pp 295ndash305 1953
[13] N I Fisher Statistical Analysis of Circular Data CambridgeUniversity Press Cambridge UK 1996
[14] G Borradaile Statistics of Earth Science Data Springer NewYork NY USA 2003
[15] K A Keating and S Cherry ldquoModeling utilization distributionsin space and timerdquo Ecology vol 90 no 7 pp 1971ndash1980 2009
[16] H-I Wu B-L Li T A Springer and W H Neill ldquoModellinganimal movement as a persistent random walk in two dimen-sions expected magnitude of net displacementrdquo EcologicalModelling vol 132 no 1-2 pp 115ndash124 2000
[17] Y Vermard E Rivot S Mahevas P Marchal and D GascuelldquoIdentifying fishing trip behaviour and estimating fishing effortfrom VMS data using Bayesian Hidden Markov ModelsrdquoEcological Modelling vol 221 no 15 pp 1757ndash1769 2010
[18] K Thorup J Raboslashl and J J Madsen ldquoCan clock-and-compassexplain the distribution of ringing recoveries of pied flycatch-ersrdquo Animal Behaviour vol 60 no 2 pp F3ndashF8 2000
[19] M P do Carmo Riemannian Geometry Birkhauser BostonMass USA 1992
[20] P Petersen Riemannian Geometry Springer New York NYUSA 2nd edition 2006
[21] C R Rao ldquoInformation and the accuracy attainable in theestimation of statistical parametersrdquo Bulletin of the CalcuttaMathematical Society vol 37 pp 81ndash91 1945
[22] W Chen and X Li Introduction to Riemannian GeometryPeking University Press Beijing China 2012
[23] D Alekseevsky ldquoRiemannian manifolds of cohomogeneityonerdquo in Proceedings of the Colloquium on Differential Geometryvol 56 of Colloeq Math Soc J Bolyai pp 9ndash22 1989
[24] A Alekseevsky and D Alekseevsky ldquoG-manifold with one-dimensional orbit spacerdquo Advances in Soviet Mathematics vol8 pp 1ndash31 1992
[25] A Besse Einstein Manifolds Springer Berlin Germany 1987[26] R L Bryant ldquoMetrics with holonomy 119866
2or spin (7)rdquo in Arbeit-
stagung Bonn 1984 vol 1111 of Lecture Notes in Mathematics pp269ndash277 Springer Berlin Germany 1985
[27] R L Bryant ldquoA survey of Riemannian metrics with specialholonomy groupsrdquo in Proceedings of the International Congressof Mathematicians vol 1 pp 505ndash514 AMS Berkeley CalifUSA 1987
[28] R L Bryant ldquoMetrics with exceptional holonomyrdquo Annals ofMathematics Second Series vol 126 no 3 pp 525ndash576 1987
[29] R Bryant and F Harvery ldquoSome remarks on the geometry ofmanifolds with exceptional holonomyrdquo preprint 1994
[30] R L Bryant and S M Salamon ldquoOn the construction ofsome complete metrics with exceptional holonomyrdquo DukeMathematical Journal vol 58 no 3 pp 829ndash850 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
4 Advances in Mathematical Physics
119892119902
((120593120572)lowast119901
(120597
1205971205791) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(minus120597
1205971205791
120597
1205971205792) = 0 = 119892
119901(
120597
1205971205791
120597
1205971205792)
119892119902
((120593120572)lowast119901
(120597
1205971205792) (120593120572)lowast119901
(120597
1205971205792))
= 119892119902
(120597
1205971205792
120597
1205971205792) =
1
2sinh21205792= 119892119901
(120597
1205971205792
120597
1205971205792)
(24)
Hence 120593120572is an isometry
As a result 119866 = 120593120572
| 120572 isin R is a subgroup of 119868(119878)Lemma 10 implies that 119878 is ldquoalmostrdquo homogeneous althoughnot truly homogeneous In fact 119878 is a cohomogeneity onemanifold defined in Definition 11
Definition 11 Let (119872 119892) be a Riemannianmanifold and 119868(119872)
is its group of isometric transformations Then 119868(119872) has anatural action Φ on 119872
Φ 119868 (119872) times 119872 997888rarr 119872 (120593 119901) 997891997888rarr 120593 (119901)
forall120593 isin 119868 (119872) 119901 isin 119872
(25)
119872 is a cohomogeneity one manifold if the codimension oforbit space of this action is 1
Remark 12 The codimension of the orbit space is closelyrelated to the homogeneous properties For example if 119872 isa homogeneous space then the orbit space is whole manifold119872 and hence its codimension is 0The less that codimensionis the more homogeneous the manifold is In other wordsa cohomogeneity one manifold is ldquothe most homogeneousmanifoldrdquo except for the real ones
Actually cohomogeneity one manifolds are natural gen-eralizations of homogeneousmanifoldsThe systematic studyof cohomogeneity onemanifolds was started by Bergery whosuccessfully constructed new invariant Einstein metrics oncohomogeneity one manifolds In addition Bryant and Sala-mon constructed special metrics with exceptional holonomygroups 119866
2and Spin(7) on these manifolds [23ndash30]
We state a well known result without proof beforeTheorem 14
Lemma 13 Every homogeneous space is complete
Theorem 14 119878 is a cohomogeneity one manifold
Proof Let 119901 = (1205791
1205792
) isin 119878 and 119868(119878)119901
= 120593(119901) | 120593 isin 119868(119878)
be its orbit space If dim(119868(119878)119901) = 2 119878 will be homogeneous
Lemma 13 implies that 119878 is complete which contradicts toTheorem 7 This contradiction implies dim(119868(119878)
119901) le 1
On the other hand
119866119901
= 120593 (119901) | 120593 isin 119866 = 120593120572
(119901) | 120572 isin R
= (2120572 minus 1205791
1205792
) | 120572 isin R = (119909 1205792
) | 119909 isin R
(26)
Since 119866 is a subgroup of 119868(119878) 119866119901
sub 119868(119878)119901 This implies that
dim (119868 (119878)119901) ge dim (119866
119901) = 1 (27)
Based on the two inequalities we conclude that dim(119868(119878)119901) =
1 hence its codimension is 1 which means that 119878 is acohomogeneity one manifold
4 Instability Analysis
In this section we will calculate some geodesics and investi-gate the instability of the geodesics by the Jacobi vector fields
Combining (12) and (17) the geodesic equations of theWCED model are given by the following differential system
d21205791
d1199052minus
2 cosh 1205792
sinh 1205792
d1205791
d119905
d1205792
d119905= 0
d21205792
d1199052+cosh 120579
2
sinh 1205792(d1205791
d119905)
2
minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(28)
Generally these equations are quite hard to be solvedhowever we can get some special geodesics based on thecohomogeneity one property
Lemma 15 All lines parallel to the y-axis are geodesics
Proof It is well known that the fixed-points set of anyisometry is a geodesic Since 120593
120572is an isometry and its fixed-
points set is the line 119909 = 1205791 the lemma follows
According to Lemma 15 the equation of such geodesicsatisfies
1205791
= 1205791
0 (29)
Hence (28) can be reduced to
d1205791
d119905= 0
d21205792
d1199052minuscosh 120579
2
sinh 1205792(d1205792
d119905)
2
= 0
(30)
Then solution is expressed as
1205791
= 1198863
1205792
= ln100381610038161003816100381610038161003816100381610038161003816
1198862exp 119886
1119905 + 1
1198862exp 119886
1119905 minus 1
100381610038161003816100381610038161003816100381610038161003816
(31)
Consider the parameter family of geodesics
F (119862) = 120579119897
(119905 119862)119897=12
(32)
where 120579119897 is a geodesic satisfying (28) and 119862 is an integration
constant vectorThe length of geodesics inF(119862) is defined as
Θ (119905 120573) = int (119892119894119895d120579119894d120579119895
)12
(33)
Advances in Mathematical Physics 5
Therefore the length of geodesics on WCED model isobtained as
Θ (119905 119862) = int
119905
0
radic11989211
(d1205791
d119905)
2
+ 11989222
(d1205792
d119905)
2
d120591 =radic21198621
2119905
(34)
where 1198621is constant In order to investigate the behavior of
two neighboring geodesics labeled by the parameter 1198621 we
consider the following difference
ΔΘ = (
radic2 (1198621
+ 1205751198621)
2minus
radic21198621
2) 119905 (35)
It is clear that ΔΘ diverges that is the length of twoneighboring geodesics with slightly different parameters 119862
1
and 1198621
+ 1205751198621differs in a remarkable way as 119905 rarr infin
The stability of the geodesics is completely determinedby the curvature of manifold Studying the stability ofdynamics means determining the evolution of perturbationsof geodesics For isotropic manifolds the geodesic spreadis unstable only if their constant sectional curvatures arenegative As long as the curvatures are negative the geodesicspread is unstable even if the manifold is no longer isotropic[19] However it is more attractive to know the divergentdegree of a geodesic
The Jacobi vector field 119869 that is the evolution perturba-tion vector satisfies the following (Jacobi) equation
nabla 120585(119905)
nabla 120585(119905)
119869 = 119877 ( 120585 (119905) 119869) 120585 (119905) (36)
where 120585(119905) is a geodesic on manifold 119872 It is also called thegeodesic derivation equation as it has close connections withthe geodesic In general the Jacobi equations are difficult tosolve but in particular this manifold has a constant negativecurvature which is of great help Given a normal geodesic 120585
and supposing 119869 is a normal Jacobi vector field along 120585(119905) then
119877 ( 120585 (119905) 119869) 120585 (119905) = 2 (119892 ( 120585 (119905) 120585 (119905)) 119869 minus 119892 ( 120585 (119905) 119869) 120585 (119905))
= 2119869
(37)
Thus the Jacobi equation is reduced to
d2119869 (119905)
d1199052minus 2119869 (119905) = 0 (38)
Choose a unit orthogonal frame 119890119894(119905) st 119890
2(119905) = 120585(119905) and
suppose
119869 (119905) = 119869119894
(119905) 119890119894(119905) (39)
Then the Jacobi equation satisfies
d21198691 (119905)d1199052
minus 21198691
(119905) = 0
1198692
(119905) = 0
(40)
The solutions are
1198691
(119905) = 1198621119890radic2119905
+ 1198622119890minusradic2119905
1198692
(119905) = 0
(41)
This means that the geodesic spread onmanifold is describedby means of an exponential order divergent Jacobi vectorfield
5 Conclusion and Remarks
In this paper we investigate the manifold of wrapped Cauchydistributions By considering the geometric structures of theWCED we conclude that the WCED is a constant negativecurvature space with119870 = minus2 By a series of lemmas and theo-rems we prove that it is a cohomogeneity one manifold Thisexample is interesting because of its statistical backgroundwhile some other examples are deliberately constructed Inaddition we calculate the geodesics and the Jacobi vector fieldby some tricks based on some special properties of 119878 As aresult the divergent behavior of geodesics can be describedas an exponential order divergent Jacobi vector field
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Authorsrsquo Contribution
The authors declare that the study was realized in collab-oration with the same responsibility All authors read andapproved the final paper
Acknowledgments
This work is supported by the National Natural ScienceFoundations of China (nos 11126161 and NSFC61440058)Beijing Higher Education Young Elite Teacher Project (noYETP 0388) and the Fundamental Research Funds for theCentral Universities (no FRF-BR-12-005)
References
[1] S Amari Differential Geometrical Methods in StatisticsSpringer Berlin Germany 1990
[2] S Amari and H Nagaoka Methods of Information Geo metryOxford University Press Oxford UK 2000
[3] T Li L Peng and H Sun ldquoThe geometric structure of theinverse gamma distributionrdquo Beitrage zur Algebra und Geome-trie vol 49 no 1 pp 217ndash225 2008
[4] L Peng H Sun D Sun and J Yi ldquoThe geometric structuresand instability of entropic dynamical modelsrdquo Advances inMathematics vol 227 no 1 pp 459ndash471 2011
[5] L Peng H Sun and G Xu ldquoInformation geometric charac-terization of the complexity of fractional Brownian motionsrdquoJournal of Mathematical Physics vol 53 no 12 Article ID123305 12 pages 2012
6 Advances in Mathematical Physics
[6] L Peng H Sun and X Sun ldquoGeometric structure of Hamilto-nian dynamics with conformal Eisenhart metricrdquo InternationalJournal of Mathematics and Mathematical Sciences vol 2011Article ID 710274 26 pages 2011
[7] A Caticha ldquoEntropic dynamicsrdquo in Bayesian Inference andMaximum Entropy Methods in Science and Engineering R LFry Ed AIP Conference Proceedings pp 617ndash302 2002
[8] C Cafaro and S A Ali ldquoJacobi fields on statistical manifolds ofnegative curvaturerdquo Physica D Nonlinear Phenomena vol 234no 1 pp 70ndash80 2007
[9] K V Mardia and P E Jupp Directional Statistics JohnWiley ampSons New York NY USA 1999
[10] C Bingham ldquoAn antipodally symmetric distribution on thesphererdquoThe Annals of Statistics vol 2 pp 1201ndash1225 1974
[11] J T Kent ldquoThe Fisher-Bingham distribution on the sphererdquoJournal of the Royal Statistical Society vol 44 pp 71ndash80 1982
[12] R A Fisher ldquoDispersion on a sphererdquo Proceedings of the RoyalSociety of London A vol 217 pp 295ndash305 1953
[13] N I Fisher Statistical Analysis of Circular Data CambridgeUniversity Press Cambridge UK 1996
[14] G Borradaile Statistics of Earth Science Data Springer NewYork NY USA 2003
[15] K A Keating and S Cherry ldquoModeling utilization distributionsin space and timerdquo Ecology vol 90 no 7 pp 1971ndash1980 2009
[16] H-I Wu B-L Li T A Springer and W H Neill ldquoModellinganimal movement as a persistent random walk in two dimen-sions expected magnitude of net displacementrdquo EcologicalModelling vol 132 no 1-2 pp 115ndash124 2000
[17] Y Vermard E Rivot S Mahevas P Marchal and D GascuelldquoIdentifying fishing trip behaviour and estimating fishing effortfrom VMS data using Bayesian Hidden Markov ModelsrdquoEcological Modelling vol 221 no 15 pp 1757ndash1769 2010
[18] K Thorup J Raboslashl and J J Madsen ldquoCan clock-and-compassexplain the distribution of ringing recoveries of pied flycatch-ersrdquo Animal Behaviour vol 60 no 2 pp F3ndashF8 2000
[19] M P do Carmo Riemannian Geometry Birkhauser BostonMass USA 1992
[20] P Petersen Riemannian Geometry Springer New York NYUSA 2nd edition 2006
[21] C R Rao ldquoInformation and the accuracy attainable in theestimation of statistical parametersrdquo Bulletin of the CalcuttaMathematical Society vol 37 pp 81ndash91 1945
[22] W Chen and X Li Introduction to Riemannian GeometryPeking University Press Beijing China 2012
[23] D Alekseevsky ldquoRiemannian manifolds of cohomogeneityonerdquo in Proceedings of the Colloquium on Differential Geometryvol 56 of Colloeq Math Soc J Bolyai pp 9ndash22 1989
[24] A Alekseevsky and D Alekseevsky ldquoG-manifold with one-dimensional orbit spacerdquo Advances in Soviet Mathematics vol8 pp 1ndash31 1992
[25] A Besse Einstein Manifolds Springer Berlin Germany 1987[26] R L Bryant ldquoMetrics with holonomy 119866
2or spin (7)rdquo in Arbeit-
stagung Bonn 1984 vol 1111 of Lecture Notes in Mathematics pp269ndash277 Springer Berlin Germany 1985
[27] R L Bryant ldquoA survey of Riemannian metrics with specialholonomy groupsrdquo in Proceedings of the International Congressof Mathematicians vol 1 pp 505ndash514 AMS Berkeley CalifUSA 1987
[28] R L Bryant ldquoMetrics with exceptional holonomyrdquo Annals ofMathematics Second Series vol 126 no 3 pp 525ndash576 1987
[29] R Bryant and F Harvery ldquoSome remarks on the geometry ofmanifolds with exceptional holonomyrdquo preprint 1994
[30] R L Bryant and S M Salamon ldquoOn the construction ofsome complete metrics with exceptional holonomyrdquo DukeMathematical Journal vol 58 no 3 pp 829ndash850 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Advances in Mathematical Physics 5
Therefore the length of geodesics on WCED model isobtained as
Θ (119905 119862) = int
119905
0
radic11989211
(d1205791
d119905)
2
+ 11989222
(d1205792
d119905)
2
d120591 =radic21198621
2119905
(34)
where 1198621is constant In order to investigate the behavior of
two neighboring geodesics labeled by the parameter 1198621 we
consider the following difference
ΔΘ = (
radic2 (1198621
+ 1205751198621)
2minus
radic21198621
2) 119905 (35)
It is clear that ΔΘ diverges that is the length of twoneighboring geodesics with slightly different parameters 119862
1
and 1198621
+ 1205751198621differs in a remarkable way as 119905 rarr infin
The stability of the geodesics is completely determinedby the curvature of manifold Studying the stability ofdynamics means determining the evolution of perturbationsof geodesics For isotropic manifolds the geodesic spreadis unstable only if their constant sectional curvatures arenegative As long as the curvatures are negative the geodesicspread is unstable even if the manifold is no longer isotropic[19] However it is more attractive to know the divergentdegree of a geodesic
The Jacobi vector field 119869 that is the evolution perturba-tion vector satisfies the following (Jacobi) equation
nabla 120585(119905)
nabla 120585(119905)
119869 = 119877 ( 120585 (119905) 119869) 120585 (119905) (36)
where 120585(119905) is a geodesic on manifold 119872 It is also called thegeodesic derivation equation as it has close connections withthe geodesic In general the Jacobi equations are difficult tosolve but in particular this manifold has a constant negativecurvature which is of great help Given a normal geodesic 120585
and supposing 119869 is a normal Jacobi vector field along 120585(119905) then
119877 ( 120585 (119905) 119869) 120585 (119905) = 2 (119892 ( 120585 (119905) 120585 (119905)) 119869 minus 119892 ( 120585 (119905) 119869) 120585 (119905))
= 2119869
(37)
Thus the Jacobi equation is reduced to
d2119869 (119905)
d1199052minus 2119869 (119905) = 0 (38)
Choose a unit orthogonal frame 119890119894(119905) st 119890
2(119905) = 120585(119905) and
suppose
119869 (119905) = 119869119894
(119905) 119890119894(119905) (39)
Then the Jacobi equation satisfies
d21198691 (119905)d1199052
minus 21198691
(119905) = 0
1198692
(119905) = 0
(40)
The solutions are
1198691
(119905) = 1198621119890radic2119905
+ 1198622119890minusradic2119905
1198692
(119905) = 0
(41)
This means that the geodesic spread onmanifold is describedby means of an exponential order divergent Jacobi vectorfield
5 Conclusion and Remarks
In this paper we investigate the manifold of wrapped Cauchydistributions By considering the geometric structures of theWCED we conclude that the WCED is a constant negativecurvature space with119870 = minus2 By a series of lemmas and theo-rems we prove that it is a cohomogeneity one manifold Thisexample is interesting because of its statistical backgroundwhile some other examples are deliberately constructed Inaddition we calculate the geodesics and the Jacobi vector fieldby some tricks based on some special properties of 119878 As aresult the divergent behavior of geodesics can be describedas an exponential order divergent Jacobi vector field
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Authorsrsquo Contribution
The authors declare that the study was realized in collab-oration with the same responsibility All authors read andapproved the final paper
Acknowledgments
This work is supported by the National Natural ScienceFoundations of China (nos 11126161 and NSFC61440058)Beijing Higher Education Young Elite Teacher Project (noYETP 0388) and the Fundamental Research Funds for theCentral Universities (no FRF-BR-12-005)
References
[1] S Amari Differential Geometrical Methods in StatisticsSpringer Berlin Germany 1990
[2] S Amari and H Nagaoka Methods of Information Geo metryOxford University Press Oxford UK 2000
[3] T Li L Peng and H Sun ldquoThe geometric structure of theinverse gamma distributionrdquo Beitrage zur Algebra und Geome-trie vol 49 no 1 pp 217ndash225 2008
[4] L Peng H Sun D Sun and J Yi ldquoThe geometric structuresand instability of entropic dynamical modelsrdquo Advances inMathematics vol 227 no 1 pp 459ndash471 2011
[5] L Peng H Sun and G Xu ldquoInformation geometric charac-terization of the complexity of fractional Brownian motionsrdquoJournal of Mathematical Physics vol 53 no 12 Article ID123305 12 pages 2012
6 Advances in Mathematical Physics
[6] L Peng H Sun and X Sun ldquoGeometric structure of Hamilto-nian dynamics with conformal Eisenhart metricrdquo InternationalJournal of Mathematics and Mathematical Sciences vol 2011Article ID 710274 26 pages 2011
[7] A Caticha ldquoEntropic dynamicsrdquo in Bayesian Inference andMaximum Entropy Methods in Science and Engineering R LFry Ed AIP Conference Proceedings pp 617ndash302 2002
[8] C Cafaro and S A Ali ldquoJacobi fields on statistical manifolds ofnegative curvaturerdquo Physica D Nonlinear Phenomena vol 234no 1 pp 70ndash80 2007
[9] K V Mardia and P E Jupp Directional Statistics JohnWiley ampSons New York NY USA 1999
[10] C Bingham ldquoAn antipodally symmetric distribution on thesphererdquoThe Annals of Statistics vol 2 pp 1201ndash1225 1974
[11] J T Kent ldquoThe Fisher-Bingham distribution on the sphererdquoJournal of the Royal Statistical Society vol 44 pp 71ndash80 1982
[12] R A Fisher ldquoDispersion on a sphererdquo Proceedings of the RoyalSociety of London A vol 217 pp 295ndash305 1953
[13] N I Fisher Statistical Analysis of Circular Data CambridgeUniversity Press Cambridge UK 1996
[14] G Borradaile Statistics of Earth Science Data Springer NewYork NY USA 2003
[15] K A Keating and S Cherry ldquoModeling utilization distributionsin space and timerdquo Ecology vol 90 no 7 pp 1971ndash1980 2009
[16] H-I Wu B-L Li T A Springer and W H Neill ldquoModellinganimal movement as a persistent random walk in two dimen-sions expected magnitude of net displacementrdquo EcologicalModelling vol 132 no 1-2 pp 115ndash124 2000
[17] Y Vermard E Rivot S Mahevas P Marchal and D GascuelldquoIdentifying fishing trip behaviour and estimating fishing effortfrom VMS data using Bayesian Hidden Markov ModelsrdquoEcological Modelling vol 221 no 15 pp 1757ndash1769 2010
[18] K Thorup J Raboslashl and J J Madsen ldquoCan clock-and-compassexplain the distribution of ringing recoveries of pied flycatch-ersrdquo Animal Behaviour vol 60 no 2 pp F3ndashF8 2000
[19] M P do Carmo Riemannian Geometry Birkhauser BostonMass USA 1992
[20] P Petersen Riemannian Geometry Springer New York NYUSA 2nd edition 2006
[21] C R Rao ldquoInformation and the accuracy attainable in theestimation of statistical parametersrdquo Bulletin of the CalcuttaMathematical Society vol 37 pp 81ndash91 1945
[22] W Chen and X Li Introduction to Riemannian GeometryPeking University Press Beijing China 2012
[23] D Alekseevsky ldquoRiemannian manifolds of cohomogeneityonerdquo in Proceedings of the Colloquium on Differential Geometryvol 56 of Colloeq Math Soc J Bolyai pp 9ndash22 1989
[24] A Alekseevsky and D Alekseevsky ldquoG-manifold with one-dimensional orbit spacerdquo Advances in Soviet Mathematics vol8 pp 1ndash31 1992
[25] A Besse Einstein Manifolds Springer Berlin Germany 1987[26] R L Bryant ldquoMetrics with holonomy 119866
2or spin (7)rdquo in Arbeit-
stagung Bonn 1984 vol 1111 of Lecture Notes in Mathematics pp269ndash277 Springer Berlin Germany 1985
[27] R L Bryant ldquoA survey of Riemannian metrics with specialholonomy groupsrdquo in Proceedings of the International Congressof Mathematicians vol 1 pp 505ndash514 AMS Berkeley CalifUSA 1987
[28] R L Bryant ldquoMetrics with exceptional holonomyrdquo Annals ofMathematics Second Series vol 126 no 3 pp 525ndash576 1987
[29] R Bryant and F Harvery ldquoSome remarks on the geometry ofmanifolds with exceptional holonomyrdquo preprint 1994
[30] R L Bryant and S M Salamon ldquoOn the construction ofsome complete metrics with exceptional holonomyrdquo DukeMathematical Journal vol 58 no 3 pp 829ndash850 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
6 Advances in Mathematical Physics
[6] L Peng H Sun and X Sun ldquoGeometric structure of Hamilto-nian dynamics with conformal Eisenhart metricrdquo InternationalJournal of Mathematics and Mathematical Sciences vol 2011Article ID 710274 26 pages 2011
[7] A Caticha ldquoEntropic dynamicsrdquo in Bayesian Inference andMaximum Entropy Methods in Science and Engineering R LFry Ed AIP Conference Proceedings pp 617ndash302 2002
[8] C Cafaro and S A Ali ldquoJacobi fields on statistical manifolds ofnegative curvaturerdquo Physica D Nonlinear Phenomena vol 234no 1 pp 70ndash80 2007
[9] K V Mardia and P E Jupp Directional Statistics JohnWiley ampSons New York NY USA 1999
[10] C Bingham ldquoAn antipodally symmetric distribution on thesphererdquoThe Annals of Statistics vol 2 pp 1201ndash1225 1974
[11] J T Kent ldquoThe Fisher-Bingham distribution on the sphererdquoJournal of the Royal Statistical Society vol 44 pp 71ndash80 1982
[12] R A Fisher ldquoDispersion on a sphererdquo Proceedings of the RoyalSociety of London A vol 217 pp 295ndash305 1953
[13] N I Fisher Statistical Analysis of Circular Data CambridgeUniversity Press Cambridge UK 1996
[14] G Borradaile Statistics of Earth Science Data Springer NewYork NY USA 2003
[15] K A Keating and S Cherry ldquoModeling utilization distributionsin space and timerdquo Ecology vol 90 no 7 pp 1971ndash1980 2009
[16] H-I Wu B-L Li T A Springer and W H Neill ldquoModellinganimal movement as a persistent random walk in two dimen-sions expected magnitude of net displacementrdquo EcologicalModelling vol 132 no 1-2 pp 115ndash124 2000
[17] Y Vermard E Rivot S Mahevas P Marchal and D GascuelldquoIdentifying fishing trip behaviour and estimating fishing effortfrom VMS data using Bayesian Hidden Markov ModelsrdquoEcological Modelling vol 221 no 15 pp 1757ndash1769 2010
[18] K Thorup J Raboslashl and J J Madsen ldquoCan clock-and-compassexplain the distribution of ringing recoveries of pied flycatch-ersrdquo Animal Behaviour vol 60 no 2 pp F3ndashF8 2000
[19] M P do Carmo Riemannian Geometry Birkhauser BostonMass USA 1992
[20] P Petersen Riemannian Geometry Springer New York NYUSA 2nd edition 2006
[21] C R Rao ldquoInformation and the accuracy attainable in theestimation of statistical parametersrdquo Bulletin of the CalcuttaMathematical Society vol 37 pp 81ndash91 1945
[22] W Chen and X Li Introduction to Riemannian GeometryPeking University Press Beijing China 2012
[23] D Alekseevsky ldquoRiemannian manifolds of cohomogeneityonerdquo in Proceedings of the Colloquium on Differential Geometryvol 56 of Colloeq Math Soc J Bolyai pp 9ndash22 1989
[24] A Alekseevsky and D Alekseevsky ldquoG-manifold with one-dimensional orbit spacerdquo Advances in Soviet Mathematics vol8 pp 1ndash31 1992
[25] A Besse Einstein Manifolds Springer Berlin Germany 1987[26] R L Bryant ldquoMetrics with holonomy 119866
2or spin (7)rdquo in Arbeit-
stagung Bonn 1984 vol 1111 of Lecture Notes in Mathematics pp269ndash277 Springer Berlin Germany 1985
[27] R L Bryant ldquoA survey of Riemannian metrics with specialholonomy groupsrdquo in Proceedings of the International Congressof Mathematicians vol 1 pp 505ndash514 AMS Berkeley CalifUSA 1987
[28] R L Bryant ldquoMetrics with exceptional holonomyrdquo Annals ofMathematics Second Series vol 126 no 3 pp 525ndash576 1987
[29] R Bryant and F Harvery ldquoSome remarks on the geometry ofmanifolds with exceptional holonomyrdquo preprint 1994
[30] R L Bryant and S M Salamon ldquoOn the construction ofsome complete metrics with exceptional holonomyrdquo DukeMathematical Journal vol 58 no 3 pp 829ndash850 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
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International Journal of Mathematics and Mathematical Sciences
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