Local Void vs Dark EnergyLocal Void vs Dark Energy
Tirthabir BiswasTirthabir Biswas
IGC, Penn-State UniversityIGC, Penn-State University
with A Notari and R Mansouri, astro-ph/0606703with A Notari and R Mansouri, astro-ph/0606703with A Notari, astro-ph/0702555with A Notari, astro-ph/0702555
with A Notari, S Alexander & D Vaid, arXiv:0712.0370with A Notari, S Alexander & D Vaid, arXiv:0712.0370
Puzzles of Dark EnergyPuzzles of Dark Energy Smallness ProblemSmallness Problem
Coincidence or Why now ProblemCoincidence or Why now Problem
These puzzles are not unique to These puzzles are not unique to ΛΛCDM…CDM…
… … we are still very much in the darkwe are still very much in the dark
Is dark energy real?Is dark energy real?
Concordant Concordant ΛΛCDMCDM Type Ia SupernovaeType Ia Supernovae WMAP (CMB)WMAP (CMB) SDSS (galaxy power spectrum)SDSS (galaxy power spectrum) LRG (Baryon acoustic peak, BAO)LRG (Baryon acoustic peak, BAO) ISW effectISW effect ……Success of Success of ΛΛCDM, failure of EdSCDM, failure of EdS
How can we even contemplate not having How can we even contemplate not having ΛΛ??What could we have missed?What could we have missed?
The Inhomogeneous The Inhomogeneous UniverseUniverse
Is homogeneity a good assumption?Is homogeneity a good assumption? Celerier ‘97Celerier ‘97 Back-reaction: “average expansion rate changes”Back-reaction: “average expansion rate changes” Rees-Schiama effect: What do we really measureRees-Schiama effect: What do we really measure
RedshiftRedshift
Luminosity DistanceLuminosity Distance
Evolution history of universe effects DEvolution history of universe effects DLL(z) , but (z) , but
Inhomogeneities also effect light paths, or DInhomogeneities also effect light paths, or DLL(z)(z)
L ~ 10-20 Mpc/h, RL ~ 10-20 Mpc/h, RHH~ 3000 Mpc/h~ 3000 Mpc/h
obs
sourcez
1
Flux Bolometric
Luminocity4 2 LD
1~ Correction23
HH R
L
R
L
LocalLocal EffectEffect: : We are sitting inside a large ~ We are sitting inside a large ~ OO(100) Mpc/h void!(100) Mpc/h void!
Non-linear evolution Non-linear evolution
Why we can still be optimistic?Why we can still be optimistic? We only need We only need
We regularly observe voids ~ We regularly observe voids ~ 50 Mpc/h50 Mpc/h, , & large structures, Great SLOAN wall ~ & large structures, Great SLOAN wall ~ 400 Mpc/h400 Mpc/h huge “hole” spanning huge “hole” spanning 150 Mpc/h150 Mpc/h, and , and 25%25% underdensity! underdensity!
[Frith et al][Frith et al]
How well do we understand nonlinear structure formation?How well do we understand nonlinear structure formation? Percolated voids ~ Percolated voids ~ 100 Mpc/h100 Mpc/h [Shandarin, Sheth and Sahni][Shandarin, Sheth and Sahni]
Having a large local void may not be as unlikelyHaving a large local void may not be as unlikely
1.0~~ Correction
HR
L
hMpcOLforO /)10(~)1(~
4.0~
Minimal Void ModelMinimal Void Model
Distant supernovae has z ~ 0.5-1 ~ O(1000) Mpc/hDistant supernovae has z ~ 0.5-1 ~ O(1000) Mpc/h Extreamely unlikelyExtreamely unlikely Would effect CMB fluctuationsWould effect CMB fluctuations ruled out by distortion of black-body spectrum ruled out by distortion of black-body spectrum [Caldwell [Caldwell
& Stebbins]& Stebbins]
We only need to modify upto z ~ 0.08 ~ O(200) Mpc/hWe only need to modify upto z ~ 0.08 ~ O(200) Mpc/h““Currently” acceleration inferred through a mismatch Currently” acceleration inferred through a mismatch
of between of between Nearby,Nearby, z < 0.08 z < 0.08 & distant ,& distant , z >0.4 z >0.4 supernovae datasupernovae data
HHout out HHin in HHout out
z<0.1z<0.1, , nearby supernova’s inside the patch, experience nearby supernova’s inside the patch, experience faster local Hubble expansionfaster local Hubble expansionz>0.1z>0.1 outside the patch, see average expansionoutside the patch, see average expansion
181...1862.1 2 fodJ
Fitting WMAPFitting WMAP
Effect of voidEffect of void Central Observer+Spherical symmetry Central Observer+Spherical symmetry only only
monopolemonopole Off-center observer Off-center observer dipole ~ 10dipole ~ 10-3-3
within within 10%10% of void-radius of void-radius [Alnes & Amarzguioui][Alnes & Amarzguioui]
Higher multipoles are much suppressedHigher multipoles are much suppressed Non-spherical voids: Interresting possibilities, Non-spherical voids: Interresting possibilities, low multipole anomalies in CMB low multipole anomalies in CMB [Silk & Inoue][Silk & Inoue] ? ? Many large voids Many large voids interesting secondary effects to interesting secondary effects to CMB anisotropies ~ 10CMB anisotropies ~ 10-5-5 , Implications for ISW , Implications for ISW
Assume spherical symmetry, EdS good enough for Assume spherical symmetry, EdS good enough for WMAPWMAP
Can EdS fit the WMAP?Can EdS fit the WMAP?Yes! Provided we give up near scale-invarianceYes! Provided we give up near scale-invariance
Include running instead of Include running instead of ΛΛ
Best fit WMAP parametersBest fit WMAP parameters
consistent with BBNconsistent with BBN Bayons constitute 9% of matter, may be too low?Bayons constitute 9% of matter, may be too low? zzrecrec ~ 13 ~ 13, broadly consistent, broadly consistent low spectral index & large running low spectral index & large running seemingly consistent with BAO seemingly consistent with BAO [Eisenstein et [Eisenstein et
al]al] 0.43< h0.43< houtout <0.47 <0.47 low Hubble parameter low Hubble parameter Along with the jump, local Along with the jump, local h ~ 0.59h ~ 0.59 possible! possible! HKP: HKP: h= .72 h= .72 .08.08 supernovae: supernovae: h= .59 h= .59 .04.04 SZ effect: SZ effect: h= .54 h= .54 .04.04
018.~2outbh
15.0~73.0~ ssn 2.0~22
outM hh
ConclusionsConclusions
SN Ia, WMAP, local h, BBN, BAO can workSN Ia, WMAP, local h, BBN, BAO can workSDSS, LRG (BAO), Lyman-SDSS, LRG (BAO), Lyman-, to be done, to be doneSeveral tests: D(z) curve, direct Several tests: D(z) curve, direct
observations of voids, correlated observations of voids, correlated anisotropies in CMB and H measurementsanisotropies in CMB and H measurements
Who knows in 5 years we may be talking Who knows in 5 years we may be talking about the mystery of the void about the mystery of the void
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