New results on probability and measures for eternal inflationquantum (coin flip, card choice etc)...
Transcript of New results on probability and measures for eternal inflationquantum (coin flip, card choice etc)...
New results on probability and measures
for eternal inflation
Andreas Albrecht UC Davis
Cosmology After Planck Workshop U. Michigan Sep 25, 2013
1 Albrecht Cosmology After Planck 9/13
Albrecht Cosmology After Planck 9/13 2
My history with this topic
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
Albrecht Cosmology After Planck 9/13 3
My history with this topic All
randomness/probabilities are
quantum (coin flip, card choice etc)
Albrecht Cosmology After Planck 9/13 4
Albrecht Cosmology After Planck 9/13 5
My history with this topic
Page: Quantum probabilities cannot
address key multiverse questions. (OK, just use classical
ones)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
Albrecht Cosmology After Planck 9/13 6
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
Albrecht Cosmology After Planck 9/13 7
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
Hartle, Srednicki, Aguirre, Tegmark, …
Albrecht Cosmology After Planck 9/13 8
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
AA: A deeper problem than the measure problems for
the multiverse
Albrecht Cosmology After Planck 9/13 9
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
AA: A deeper problem than the measure problems for
the multiverse A potential issue even for finite models
Albrecht Cosmology After Planck 9/13 10
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
AA: A deep problem than the
measure problems for the
multiverse AA: Write
paper explaining this with Phillips
Albrecht Cosmology After Planck 9/13 11
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
AA: A deep problem than the
measure problems for the
multiverse AA: Write paper
explaining this with Phillips
AA: This is fundamentally about giving permission to dismiss certain probability
questions (the non quantum ones) as “ill posed”.
Albrecht Cosmology After Planck 9/13 12
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
AA: A deep problem than the
measure problems for the
multiverse AA: Write paper
explaining this with Phillips
AA: This is fundamentally about giving permission to dismiss certain probability
questions (the non quantum ones) as “ill
posed”.
Perhaps this type of discipline can help
resolve the measure problems of the
multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 13
My history with this topic
Page: Quantum probabilities
cannot address key multiverse
questions. (OK, just use
classical ones)
AA: All randomness/
probabilities are quantum (coin flip, card choice
etc)
All randomness/proba
bilities are quantum (coin flip,
card choice etc)
AA: A deep problem than the
measure problems for the
multiverse AA: Write paper
explaining this with Phillips
AA: This is fundamentally about giving permission to dismiss certain probability
questions (the non quantum ones) as “ill
posed”.
Perhaps this type of discipline can help
resolve the measure problems of the
multiverse/eternal inflation
X ?
Albrecht Cosmology After Planck 9/13 14
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 15
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
NB: Very different subject from “make probabilities
precise” in “Stanford sense”.
Albrecht Cosmology After Planck 9/13 16
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 17
Planck Data --- Cosmic Inflation theory
-200 -100 0 100 2000
0.5
1
1.5
2
2.5x 10
4
/MP
V/M
GU
T
4
Slow rolling of inflaton
Albrecht Cosmology After Planck 9/13 18
Observable physics
generated here
-200 -100 0 100 2000
0.5
1
1.5
2
2.5x 10
4
/MP
V/M
GU
T
4
Slow rolling of inflaton
Albrecht Cosmology After Planck 9/13 19
Observable physics
generated here Extrapolating
back
-200 -100 0 100 2000
0.5
1
1.5
2
2.5x 10
4
/MP
V/M
GU
T
4
Slow rolling of inflaton
Q
Albrecht Cosmology After Planck 9/13 20
“Self-reproducing regime” (dominated by quantum
fluctuations): Eternal inflation/Multiverse
Observable physics
generated here Extrapolating
back
Steinhardt 1982, Linde 1982, Vilenkin 1983, and (then) many others
Classically Rolling
A
Self-reproduction regime
21 Albrecht Cosmology After Planck 9/13
Classically Rolling
C
Classically Rolling
B
Classically Rolling
D
The multiverse of eternal inflation with multiple classical rolling directions
Where are we? (Young universe, old universe, curvature, physical properties A, B, C, D, etc)
Classically Rolling
A
Self-reproduction regime
22 Albrecht Cosmology After Planck 9/13
Classically Rolling
C
Classically Rolling
B
Classically Rolling
D
The multiverse of eternal inflation with multiple classical rolling directions
Where are we? (Young universe, old universe, curvature, physical properties A, B, C, D, etc)
“Where are we?” Expect the theory to give you a probability distribution in this space… hopefully with some sharp predictions
Classically Rolling
A
Self-reproduction regime
23 Albrecht Cosmology After Planck 9/13
Classically Rolling
C
Classically Rolling
B
Classically Rolling
D
The multiverse of eternal inflation with multiple classical rolling directions
Where are we? (Young universe, old universe, curvature, physical properties A, B, C, D, etc)
“Where are we?” Expect the theory to give you a probability distribution in this space… hopefully with some sharp predictions
String theory landscape even more complicated (e.g. many
types of eternal inflation)
Quantum vs Non-Quantum probabilities
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Page, 2009; These slides follow AA & Phillips 2012
Albrecht Cosmology After Planck 9/13 24
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U: ˆijP ij ij
Albrecht Cosmology After Planck 9/13 25
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
ˆijP ij ij
Albrecht Cosmology After Planck 9/13 26
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
Could Write
ˆ ˆ ˆA B
i A i B iP p P p P
ˆijP ij ij
Albrecht Cosmology After Planck 9/13 27
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
Could Write
ˆ ˆ ˆA B
i A i B iP p P p P
ˆijP ij ij
Classical Probabilities to measure
A, B
Albrecht Cosmology After Planck 9/13 28
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
Could Write
ˆ ˆ ˆA B
i A i B iP p P p P
ˆijP ij ij
ˆ ˆ ˆi j ij jPP P
Classical Probabilities to measure
A, B
Does not represent a
quantum measurement
Albrecht Cosmology After Planck 9/13 29
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
Could Write
ˆ ˆ ˆA B
i A i B iP p P p P
ˆijP ij ij
ˆ ˆ ˆi j ij jPP P
Classical Probabilities to measure
A, B
Does not represent a
quantum measurement
Page: The multiverse requires
this (are you in pocket universe A
or B?)
Albrecht Cosmology After Planck 9/13 30
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
Could Write
ˆ ˆ ˆA B
i A i B iP p P p P
ˆijP ij ij
ˆ ˆ ˆi j ij jPP P
Classical Probabilities to measure
A, B
Does not represent a
quantum measurement
Page: The multiverse requires
this (are you in pocket universe A
or B?)
Albrecht Cosmology After Planck 9/13 31
• All everyday probabilities are quantum probabilities
AA & D. Phillips 2012 Albrecht Cosmology After Planck 9/13 32
• All everyday probabilities are quantum probabilities
AA & D. Phillips 2012 Albrecht Cosmology After Planck 9/13 33
Our *only* experiences with successful practical
applications of probabilities are with quantum
probabilities
• All everyday probabilities are quantum probabilities
• One should not use ideas from everyday probabilities to justify probabilities that have been proven to have no quantum origin
AA & D. Phillips 2012 Albrecht Cosmology After Planck 9/13 34
• All everyday probabilities are quantum probabilities
• One should not use ideas from everyday probabilities to justify probabilities that have been proven to have no quantum origin
AA & D. Phillips 2012
A problem for many
multiverse theories
Albrecht Cosmology After Planck 9/13 35
• All everyday probabilities are quantum probabilities
• One should not use ideas from everyday probabilities to justify probabilities that have been proven to have no quantum origin
AA & D. Phillips 2012
A problem for many
multiverse theories
Albrecht Cosmology After Planck 9/13 36
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
Could Write
ˆ ˆ ˆA B
i A i B iP p P p P
ˆijP ij ij
ˆ ˆ ˆi j ij jPP P
Classical Probabilities to measure
A, B
Does not represent a
quantum measurement
Page: The multiverse requires
this (are you in pocket universe A
or B?)
Albrecht Cosmology After Planck 9/13 37
Quantum vs Non-Quantum probabilities
ˆ 1 1 2 2A AA B
iP i i i i i i 1
ˆ 1 1 2 2B BB A
iP i i i i i i 1
Non-Quantum probabilities in a toy model:
U A B : 1 , 2A A
A : 1 , 2B B
B
: 11 , 12 , 21 , 22UA B
ij i j
Possible Measurements Projection operators:
Measure A only:
Measure B only:
Measure entire U:
BUT: It is impossible to construct a projection operator for the case where you do not know whether it is A or B that is being measured.
Could Write
ˆ ˆ ˆA B
i A i B iP p P p P
ˆijP ij ij
ˆ ˆ ˆi j ij jPP P
Classical Probabilities to measure
A, B
Does not represent a
quantum measurement
Page: The multiverse requires
this (are you in pocket universe A
or B?)
Albrecht Cosmology After Planck 9/13 38
Where do these come from
anyway?
Albrecht Cosmology After Planck 9/13 39
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 40
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Quantum effects in a billiard gas
l
Albrecht Cosmology After Planck 9/13 41
b
r
Quantum effects in a billiard gas
lQuantum Uncertainties
Albrecht Cosmology After Planck 9/13 42
b
r
b
Quantum effects in a billiard gas
l
r
pb x t
m
Albrecht Cosmology After Planck 9/13 43
Quantum effects in a billiard gas
l
22
p lb x t a
m a mv
2
2exp
2
x
a
Albrecht Cosmology After Planck 9/13 44
b
r
Quantum effects in a billiard gas
l
min 3/2
22
2 / 22
dB
p lb x t a
m a mv
ll
mv
Albrecht Cosmology After Planck 9/13 45
b
r
2
2exp
2
x
a
Quantum effects in a billiard gas
l
min 3/2
22
2 / 22
dB
p lb x t a
m a mv
ll
mv
Albrecht Cosmology After Planck 9/13 46
b
r
2
2exp
2
x
a
Minimizing conservative estimates for my purposes (also motivated by decoherence in some cases)
1b
Quantum effects in a billiard gas
l
Albrecht Cosmology After Planck 9/13 47
b
r
Subsequent collisions amplify the initial uncertainty (treat later collisions classically additional conservatism)
1b
Quantum effects in a billiard gas
l
1 2 /n
nb b l r
After n collisions:
Albrecht Cosmology After Planck 9/13 48
b
r
Quantum effects in a billiard gas
Qn is the number of collisions so that Qnb r
log
2log 1
Q
b
rn
l
r
(full quantum uncertainty as to which is the next collision)
Albrecht Cosmology After Planck 9/13 49
Air
Water
Billiards
Bumper Car
r l m v dB b Qn
for a number of physical systems Qn(all units MKS)
Albrecht Cosmology After Planck 9/13 50
Air
Water
Billiards
Bumper Car
r l m v dB b Qn
for a number of physical systems Qn(all units MKS)
1 2 150 0.5 361.4 10 183.4 10 25
Albrecht Cosmology After Planck 9/13 51
Air
Water
Billiards
Bumper Car
r l m v dB b Qn
for a number of physical systems Qn(all units MKS)
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Albrecht Cosmology After Planck 9/13 52
Air
Water
Billiards
Bumper Car
r l m v dB b Qn
for a number of physical systems Qn(all units MKS)
103.0 10105.4 10 263 10 460 127.6 10 101.3 10 0.6
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Albrecht Cosmology After Planck 9/13 53
Air
Water
Billiards
Bumper Car
r l m101.6 10
73.4 10 264.7 10
v dB b Qn360
for a number of physical systems Qn(all units MKS)
126.2 10 92.9 10 0.3
103.0 10105.4 10 263 10 460 127.6 10 101.3 10 0.6
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Albrecht Cosmology After Planck 9/13 54
Air
Water
Billiards
Bumper Car
r l m101.6 10
73.4 10 264.7 10
v dB b Qn360
for a number of physical systems Qn(all units MKS)
126.2 10 92.9 10 0.3
103.0 10105.4 10 263 10 460 127.6 10 101.3 10 0.6
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Quantum at every collision
Albrecht Cosmology After Planck 9/13 55
Air
Water
Billiards
Bumper Car
r l m101.6 10
73.4 10 264.7 10
v dB b Qn360
for a number of physical systems Qn(all units MKS)
126.2 10 92.9 10 0.3
103.0 10105.4 10 263 10 460 127.6 10 101.3 10 0.6
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Quantum at every collision
Albrecht Cosmology After Planck 9/13 56
(𝑛𝑄 < 1
breakdown of formula, but conclusion
robust)
Air
Water
Billiards
Bumper Car
r l m101.6 10
73.4 10 264.7 10
v dB b Qn360
for a number of physical systems Qn(all units MKS)
126.2 10 92.9 10 0.3
103.0 10105.4 10 263 10 460 127.6 10 101.3 10 0.6
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Quantum at every collision Every
Brownian Motion is a
“Schrödinger Cat”
Albrecht Cosmology After Planck 9/13 57
Air
Water
Billiards
Bumper Car
r l m101.6 10
73.4 10 264.7 10
v dB b Qn360
for a number of physical systems Qn(all units MKS)
126.2 10 92.9 10 0.3
103.0 10105.4 10 263 10 460 127.6 10 101.3 10 0.6
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Quantum at every collision Every
Brownian Motion is a
“Schrödinger Cat”
Albrecht Cosmology After Planck 9/13 58 Albrecht @ ICTP, Trieste 7/23/13 58
(independent of “interpretation”)
10,000,000,000,00
Air
Water
Billiards
Bumper Car
r l m101.6 10
73.4 10 264.7 10
v dB b Qn360
for a number of physical systems Qn(all units MKS)
126.2 10 92.9 10 0.3
103.0 10105.4 10 263 10 460 127.6 10 101.3 10 0.6
0.029 1 0.16 1 346.6 10 175.1 10 8
1 2 150 0.5 361.4 10 183.4 10 25
Quantum at every collision Every
Brownian Motion is a
“Schrödinger Cat”
This result is at the root of our claim that
all everyday probabilities are
quantum
Albrecht Cosmology After Planck 9/13 59
An important role for Brownian motion: Uncertainty in neuron transmission times
Brownian motion of polypeptides determines exactly how many of them are blocking ion channels in neurons at any given time. This is believed to be the dominant source of neuron transmission time uncertainties 1nt ms
Image from http://www.nature.com/nrn/journal/v13/n4/full/nrn3209.html Albrecht Cosmology After Planck 9/13 60
Analysis of coin flip
hv
fv
Coin diameter d
hf n
h f
vt t
v v
2t ft t
4 fvf
d
0.5tN f t
Using:
1nt ms 5 /h fv v m s
0.01d mAlbrecht Cosmology After Planck 9/13 61
Analysis of coin flip
hv
fv
Coin diameter d
hf n
h f
vt t
v v
2t ft t
4 fvf
d
0.5tN f t
Using:
1nt ms 5 /h fv v m s
0.01d m
50-50 coin flip probabilities are
a derivable quantum result
Albrecht Cosmology After Planck 9/13 62
Analysis of coin flip
hv
fv
Coin diameter d
hf n
h f
vt t
v v
2t ft t
4 fvf
d
0.5tN f t
Using:
1nt ms 5 /h fv v m s
0.01d m
50-50 coin flip probabilities are
a derivable quantum result
Albrecht Cosmology After Planck 9/13 63
Without reference to “principle of
indifference” etc. etc.
Analysis of coin flip
hv
fv
Coin diameter d
hf n
h f
vt t
v v
2t ft t
4 fvf
d
0.5tN f t
Using:
1nt ms 5 /h fv v m s
0.01d mAlbrecht Cosmology After Planck 9/13 64
NB: Coin flip is “at the margin” of deterministic vs random: Increasing d or deceasing vh can reduce δN substantially
Analysis of coin flip
hv
fv
Coin diameter d
hf n
h f
vt t
v v
2t ft t
4 fvf
d
0.5tN f t
Using:
1nt ms 5 /h fv v m s
0.01d mAlbrecht Cosmology After Planck 9/13 65
NB: Coin flip is “at the margin” of deterministic vs random: Increasing d or deceasing vh can reduce δN substantially
Still, this is a good illustration of how quantum uncertainties can filter up into the macroscopic world, for
systems that *are* random.
Analysis of coin flip
hv
fv
Coin diameter d
hf n
h f
vt t
v v
2t ft t
4 fvf
d
0.5tN f t
Using:
1nt ms 5 /h fv v m s
0.01d mAlbrecht Cosmology After Planck 9/13 66
NB: Coin flip is “at the margin” of deterministic vs random: Increasing d or deceasing vh can reduce δN substantially
Still, this is a good illustration of how quantum uncertainties can filter up into the macroscopic world, for
systems that *are* random.
Albrecht Cosmology After Planck 9/13 67
Physical vs probabilities vs “probabilities of belief”
Bayes:
||
P Data TheoryP Theory Data P Theory
P Data
Physical probability: To do with physical properties of detector etc
Albrecht Cosmology After Planck 9/13 68
Physical vs probabilities vs “probabilities of belief”
Bayes:
||
P Data TheoryP Theory Data P Theory
P Data
Probabilities of belief: • Which data you trust most • Which theory you like best
Albrecht Cosmology After Planck 9/13 69
Physical vs probabilities vs “probabilities of belief”
Bayes:
This talk is about physical probability only
||
P Data TheoryP Theory Data P Theory
P Data
Albrecht Cosmology After Planck 9/13 70
Physical vs probabilities vs “probabilities of belief”
Bayes:
NB: The goal of science is to get sufficiently good data that probabilities of belief are inconsequential
||
P Data TheoryP Theory Data P Theory
P Data
Albrecht Cosmology After Planck 9/13 71
Physical vs probabilities vs “probabilities of belief”
Bayes:
NB: The goal of science is to get sufficiently good data that probabilities of belief are inconsequential
||
P Data TheoryP Theory Data P Theory
P Data
Albrecht Cosmology After Planck 9/13 72
Physical vs probabilities vs “probabilities of belief”
Adding new data (theory priors can include earlier data sets):
5
5 5 4
5
||
P D TP T D P T
P D
4
4 4 3
4
||
P D TP T D P T
P D
Albrecht Cosmology After Planck 9/13 73
Physical vs probabilities vs “probabilities of belief”
Adding new data (theory priors can include earlier data sets):
5
5 5 4
5
||
P D TP T D P T
P D
4
4 4 3
4
||
P D TP T D P T
P D
1
1 1 0
1
||
P D TP T D P T
P D
Albrecht Cosmology After Planck 9/13 74
Physical vs probabilities vs “probabilities of belief”
Adding new data (theory priors can include earlier data sets):
5
5 5 4
5
||
P D TP T D P T
P D
4
4 4 3
4
||
P D TP T D P T
P D
1
1 1 0
1
||
P D TP T D P T
P D
This initial “model uncertainty” prior is the only P(T) that is a pure probability of belief.
Albrecht Cosmology After Planck 9/13 75
Physical vs probabilities vs “probabilities of belief”
Adding new data (theory priors can include earlier data sets):
5
5 5 4
5
||
P D TP T D P T
P D
4
4 4 3
4
||
P D TP T D P T
P D
1
1 1 0
1
||
P D TP T D P T
P D
This initial “model uncertainty” prior is the only P(T) that is a pure probability of belief.
This talk is only about wherever it appears
|P D T
Albrecht Cosmology After Planck 9/13 76
Physical vs probabilities vs “probabilities of belief”
Adding new data (theory priors can include earlier data sets):
5
5 5 4
5
||
P D TP T D P T
P D
4
4 4 3
4
||
P D TP T D P T
P D
1
1 1 0
1
||
P D TP T D P T
P D
This initial “model uncertainty” prior is the only P(T) that is a pure probability of belief.
This talk is only about wherever it appears
|P D T
NB: The goal of science is to get sufficiently good data that probabilities of belief are inconsequential
Albrecht Cosmology After Planck 9/13 77
Physical vs probabilities vs “probabilities of belief”
Adding new data (theory priors can include earlier data sets):
5
5 5 4
5
||
P D TP T D P T
P D
4
4 4 3
4
||
P D TP T D P T
P D
1
1 1 0
1
||
P D TP T D P T
P D
This initial “model uncertainty” prior is the only P(T) that is a pure probability of belief.
This talk is only about wherever it appears
|P D T
NB: The goal of science is to get sufficiently good data that probabilities of belief are inconsequential
This is the only part of the formula where physical
randomness appears
Albrecht Cosmology After Planck 9/13 78
Physical vs probabilities vs “probabilities of belief”
Adding new data (theory priors can include earlier data sets):
5
5 5 4
5
||
P D TP T D P T
P D
4
4 4 3
4
||
P D TP T D P T
P D
1
1 1 0
1
||
P D TP T D P T
P D
This initial “model uncertainty” prior is the only P(T) that is a pure probability of belief.
This talk is only about wherever it appears
|P D T
NB: The goal of science is to get sufficiently good data that probabilities of belief are inconsequential
This is the only part of the formula where physical
randomness appears
• Proof by exhaustion not realistic
All everyday probabilities are quantum probabilities
Albrecht Cosmology After Planck 9/13 79
• Proof by exhaustion not realistic • One counterexample (practical utility of non-quantum
probabilities) will undermine our entire argument.
All everyday probabilities are quantum probabilities
Albrecht Cosmology After Planck 9/13 80
• Proof by exhaustion not realistic • One counterexample (practical utility of non-quantum
probabilities) will undermine our entire argument • Can still invent classical probabilities just to do multiverse
cosmology
All everyday probabilities are quantum probabilities
Albrecht Cosmology After Planck 9/13 81
• Proof by exhaustion not realistic • One counterexample (practical utility of non-quantum
probabilities) will undermine our entire argument • Can still invent classical probabilities just to do multiverse
cosmology • Not a problem for many finite theories (AA, Banks &
Fischler)
All everyday probabilities are quantum probabilities
Albrecht Cosmology After Planck 9/13 82
• Proof by exhaustion not realistic • One counterexample (practical utility of non-quantum
probabilities) will undermine our entire argument • Can still invent classical probabilities just to do multiverse
cosmology • Not a problem for many finite theories (AA, Banks &
Fischler) • Which theories really do require classical probabilities
not yet resolved rigorously.
All everyday probabilities are quantum probabilities
Albrecht Cosmology After Planck 9/13 83
• Proof by exhaustion not realistic • One counterexample (practical utility of non-quantum
probabilities) will undermine our entire argument • Can still invent classical probabilities just to do multiverse
cosmology • Not a problem for many finite theories (AA, Banks &
Fischler) • Which theories really do require classical probabilities
not yet resolved rigorously (symmetry?... simplicity? See below)
All everyday probabilities are quantum probabilities
Albrecht Cosmology After Planck 9/13 84
Albrecht Cosmology After Planck 9/13 85
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 86
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 87
Central message: • “Randomness is (quantum) physics” • Counting may or MAY NOT have a role in
inferring or representing physical randomness
Heads
Albrecht Cosmology After Planck 9/13 88
Central message: • “Randomness is (quantum) physics” • Counting may or MAY NOT have a role in
inferring or representing physical randomness • Example: Flip a coin and choose a ball:
Heads
Tails
Results
Albrecht Cosmology After Planck 9/13 89
Central message: • “Randomness is (quantum) physics” • Counting may or MAY NOT have a role in
inferring or representing physical randomness • Example: Flip a coin and choose a ball:
Heads
Tails Counts of red & green
balls here can be related in very
concrete terms to the probability of heads
vs tails
Albrecht Cosmology After Planck 9/13 90
Central message: • “Randomness is (quantum) physics” • Counting may or MAY NOT have a role in
inferring or representing physical randomness • Example: Flip a coin and choose a ball:
Heads
Tails Counts of red & green
balls here can be related in very
concrete terms to the probability of heads
vs tails
91
Now ask: What is the probability that a ball drawn from the “Results” bowl is red?
Heads Albrecht Cosmology After Planck 9/13
Results
92
Now ask: What is the probability that a ball drawn from the “Results” bowl is red? • Different physical “completions” of this question are
possible which give different answers. (≈ measures)
Heads
Tails
Albrecht Cosmology After Planck 9/13
Results
Results Results
93
Now ask: What is the probability that a ball drawn from the “Results” bowl is red? • Different physical “completions” of this question are
possible which give different answers. (≈ measures) • Counting is NOT enough.
Heads
Tails
Albrecht Cosmology After Planck 9/13
Results
Results Results
94
Now ask: What is the probability that a ball drawn from the “Results” bowl is red? • Different physical “completions” of this question are
possible which give different answers. (≈ measures) • Counting is NOT enough.
Heads
Tails
Albrecht Cosmology After Planck 9/13
Results
Results Results In a multiverse with many copies
of you, there simply is *no* physical completion for the
question “which observer am I?”. Future data may address this, but not in time to make predictions.
95
Now ask: What is the probability that a ball drawn from the “Results” bowl is red? • Different physical “completions” of this question are
possible which give different answers. (≈ measures) • Counting is NOT enough.
Heads
Tails
Albrecht Cosmology After Planck 9/13
Results
Results Results In a multiverse with many copies
of you, there simply is *no* physical completion for the
question “which observer am I?”. Future data may address this, but not in time to make predictions.
96
Now ask: What is the probability that a ball drawn from the “Results” bowl is red? • Different physical “completions” of this question are
possible which give different answers. (≈ measures) • Counting is NOT enough.
Heads
Tails
Albrecht Cosmology After Planck 9/13
Results
Results Results In a multiverse with many copies
of you, there simply is *no* physical completion for the
question “which observer am I?”. Future data may address this, but not in time to make predictions.
This is where things go wrong in the
standard treatment of the multiverse
97
Now ask: What is the probability that a ball drawn from the “Results” bowl is red? • Different physical “completions” of this question are
possible which give different answers. (≈ measures) • Counting is NOT enough.
Heads
Tails
Albrecht Cosmology After Planck 9/13
Results
Results Results In a multiverse with many copies
of you, there simply is *no* physical completion for the
question “which observer am I?”. Future data may address this, but not in time to make predictions.
This is where things go wrong in the
standard treatment of the multiverse
In many cases counting observers has no predictive
value
Albrecht Cosmology After Planck 9/13 98
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 99
Outline 1) Quantum vs non-quantum probabilities (toy model/multiverse)
2) Everyday probabilities
3) Be careful about counting!
4) Implications for multiverse/eternal inflation
Albrecht Cosmology After Planck 9/13 100
Pocket A with Ap
Pocket B with Bp
100
100
100
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
Albrecht Cosmology After Planck 9/13 101
Pocket A with Ap
Pocket B with Bp
101
101
101
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation One semiclassical universe having many more possible observers in it than another (often counted
by volume), does *not* give that universe greater statistical weight. Quantum branching ratio into one
vs the other ( ) does count /A Bp p
Albrecht Cosmology After Planck 9/13 102
Pocket A with Ap
Pocket B with Bp
102
102
102
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
Albrecht Cosmology After Planck 9/13 103
Pocket A with Ap Pocket B with Bp
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
Albrecht Cosmology After Planck 9/13 104
Pocket A with Ap Pocket B with Bp
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
This model has no “Boltzmann Brain” problem as long as
Is not too small
/A Bp p
Albrecht Cosmology After Planck 9/13 105
Pocket A with Ap Pocket B with Bp
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
This model has no “Boltzmann Brain” problem as long as
Is not too small
/A Bp p
Boltzmann brains are observers which look good vs current data but which
quickly go bad
Albrecht Cosmology After Planck 9/13 106
Pocket A with Ap Pocket B with Bp
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
Albrecht Cosmology After Planck 9/13 107
More pocket universes produced later vs earlier (due to more inflation)
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
Albrecht Cosmology After Planck 9/13 108
More pocket universes produced later vs earlier (due to more inflation) & experience any time cutoff
Time cutoff regulator
1) No “volume factors” 2) Boltzmann Brain problem reduced 3) No “youngness/end of time” problem
Implications for eternal inflation
Albrecht Cosmology After Planck 9/13 109
More pocket universes produced later vs earlier (due to more inflation) & experience any time cutoff
Time cutoff regulator
Counting does not give you weightings or probabilities
Time cutoff only there to help you count
The youngness/end of time problem is simply wrong thinking.
1) All practically applicable probabilities are of physics (quantum) origin.
2) Counting of objects may or MAY NOT be a way of accessing legitimate quantum probabilities
3) Standard discussions of probabilities in cosmology often make errors re 2)
4) 1) and care about 2) allow us to introduce better discipline into cosmological discussions (just say “no”). Implications so far:
a) No (counting based) volume factors b) Reduced Boltzmann Brain problem c) No youngness/end of time problem
Conclusions
Albrecht Cosmology After Planck 9/13 110
1) All practically applicable probabilities are of physics (quantum) origin.
2) Counting of objects may or MAY NOT be a way of accessing legitimate quantum probabilities
3) Standard discussions of probabilities in cosmology often make errors re 2)
4) 1) and care about 2) allow us to introduce better discipline into cosmological discussions (just say “no”). Implications so far:
a) No (counting based) volume factors b) Reduced Boltzmann Brain problem c) No youngness/end of time problem
Conclusions
Albrecht Cosmology After Planck 9/13 111
I still have other concerns about eternal inflation that
makes me prefer finite theories, but this “probability
discipline” may resolve what I used to think was the most
troubling issue
1) All practically applicable probabilities are of physics (quantum) origin.
2) Counting of objects may or MAY NOT be a way of accessing legitimate quantum probabilities
3) Standard discussions of probabilities in cosmology often make errors re 2)
4) 1) and care about 2) allow us to introduce better discipline into cosmological discussions (just say “no”). Implications so far:
a) No (counting based) volume factors b) Reduced Boltzmann Brain problem c) No youngness/end of time problem
Conclusions
Albrecht Cosmology After Planck 9/13 112
Perhaps related to work by Nomura and
Garriga & Vilenkin and collaborators
I still have other concerns about eternal inflation that
makes me prefer finite theories, but this “probability
discipline” may resolve what I used to think was the most
troubling issue
1) All practically applicable probabilities are of physics (quantum) origin.
2) Counting of objects may or MAY NOT be a way of accessing legitimate quantum probabilities
3) Standard discussions of probabilities in cosmology often make errors re 2)
4) 1) and care about 2) allow us to introduce better discipline into cosmological discussions (just say “no”). Implications so far:
a) No (counting based) volume factors b) Reduced Boltzmann Brain problem c) No youngness/end of time problem
Conclusions
Albrecht Cosmology After Planck 9/13 113
-60 -50 -40 -30 -20 -10 0 10-70
-60
-50
-40
-30
-20
-10
0
10
log(a/a0)
log(R
H/R
H0)
Here
Cosmic structure
Albrecht Cosmology After Planck 9/13 114
Co
smic
len
gth
sca
le
Scale factor (measures expansion, time)
Today
Observable Structure
SBB
HR
Cosmic structure originates “superhorizon” in Standard Big Bag
(why would they be quantum?)
A note on “probability censorship”
-60 -50 -40 -30 -20 -10 0 10-70
-60
-50
-40
-30
-20
-10
0
10
log(a/a0)
log(R
H/R
H0)
Here
Cosmic structure
Albrecht Cosmology After Planck 9/13 115
Co
smic
len
gth
sca
le
Scale factor (measures expansion, time)
Today
Observable Structure
SBB
HR
Cosmic structures originate “superhorizon” in Standard Big Bag
(why would they be quantum?) Inf
HR
Cosmic structure originates in quantum
ground state in inflationary cosmology
A note on “probability censorship”
• Proof by exhaustion not realistic • One counterexample (practical utility of non-quantum
probabilities) will undermine our entire argument • Can still invent classical probabilities just to do multiverse
cosmology • Not a problem for many finite theories (AA, Banks &
Fischler) • Which theories really do require classical probabilities
not yet resolved rigorously (symmetry?... simplicity? See below)
All everyday probabilities are quantum probabilities
Albrecht Cosmology After Planck 9/13 116
Compare with identical particle statistics
Albrecht Cosmology After Planck 9/13 117
3.141592653589793238462643383279502884197169399375105820974944592307816406286 208998628034825342117067982148086513282306647093844609550582231725359408128481 117450284102701938521105559644622948954930381964428810975665933446128475648233 786783165271201909145648566923460348610454326648213393607260249141273724587006 606315588174881520920962829254091715364367892590360011330530548820466521384146 951941511609433057270365759591953092186117381932611793105118548074462379962749 567351885752724891227938183011949129833673362440656643086021394946395224737190 702179860943702770539217176293176752384674818467669405132000568127145263560827 785771342757789609173637178721468440901224953430146549585371050792279689258923 542019956112129021960864034418159813629774771309960518707211349999998372978049 951059731732816096318595024459455346908302642522308253344685035261931188171010 003137838752886587533208381420617177669147303598253490428755468731159562863882 353787593751957781857780532171226806613001927876611195909216420198938095257201 065485863278865936153381827968230301952035301852968995773622599413891249721775 283479131515574857242454150695950829533116861727855889075098381754637464939319 255060400927701671139009848824012858361603563707660104710181942955596198946767 837449448255379774726847104047534646208046684259069491293313677028989152104752 162056966024058038150193511253382430035587640247496473263914199272604269922796 782354781636009341721641219924586315030286182974555706749838505494588586926995 690927210797509302955321165344987202755960236480665499119881834797753566369807 426542527862551818417574672890977772793800081647060016145249192173217214772350 141441973568548161361157352552133475741849468438523323907394143334547762416862 518983569485562099219222184272550254256887671790494601653466804988627232791786 085784383827967976681454100953883786360950680064225125205117392984896084128488 626945604241965285022210661186306744278622039194945047123713786960956364371917 287467764657573962413890865832645995813390478027590099465764078951269468398352 595709825822620522489407726719478268482601476990902640136394437455305068203496
Further discussion
Bet on the millionth digit of π (or Chaitin’s Ω)
Albrecht Cosmology After Planck 9/13 118
3.141592653589793238462643383279502884197169399375105820974944592307816406286 208998628034825342117067982148086513282306647093844609550582231725359408128481 117450284102701938521105559644622948954930381964428810975665933446128475648233 786783165271201909145648566923460348610454326648213393607260249141273724587006 606315588174881520920962829254091715364367892590360011330530548820466521384146 951941511609433057270365759591953092186117381932611793105118548074462379962749 567351885752724891227938183011949129833673362440656643086021394946395224737190 702179860943702770539217176293176752384674818467669405132000568127145263560827 785771342757789609173637178721468440901224953430146549585371050792279689258923 542019956112129021960864034418159813629774771309960518707211349999998372978049 951059731732816096318595024459455346908302642522308253344685035261931188171010 003137838752886587533208381420617177669147303598253490428755468731159562863882 353787593751957781857780532171226806613001927876611195909216420198938095257201 065485863278865936153381827968230301952035301852968995773622599413891249721775 283479131515574857242454150695950829533116861727855889075098381754637464939319 255060400927701671139009848824012858361603563707660104710181942955596198946767 837449448255379774726847104047534646208046684259069491293313677028989152104752 162056966024058038150193511253382430035587640247496473263914199272604269922796 782354781636009341721641219924586315030286182974555706749838505494588586926995 690927210797509302955321165344987202755960236480665499119881834797753566369807 426542527862551818417574672890977772793800081647060016145249192173217214772350 141441973568548161361157352552133475741849468438523323907394143334547762416862 518983569485562099219222184272550254256887671790494601653466804988627232791786 085784383827967976681454100953883786360950680064225125205117392984896084128488 626945604241965285022210661186306744278622039194945047123713786960956364371917 287467764657573962413890865832645995813390478027590099465764078951269468398352 595709825822620522489407726719478268482601476990902640136394437455305068203496
Further discussion
Bet on the millionth digit of π (or Chaitin’s Ω) • The *only* thing random is the choice of digit to bet on
Albrecht Cosmology After Planck 9/13 119
3.141592653589793238462643383279502884197169399375105820974944592307816406286 208998628034825342117067982148086513282306647093844609550582231725359408128481 117450284102701938521105559644622948954930381964428810975665933446128475648233 786783165271201909145648566923460348610454326648213393607260249141273724587006 606315588174881520920962829254091715364367892590360011330530548820466521384146 951941511609433057270365759591953092186117381932611793105118548074462379962749 567351885752724891227938183011949129833673362440656643086021394946395224737190 702179860943702770539217176293176752384674818467669405132000568127145263560827 785771342757789609173637178721468440901224953430146549585371050792279689258923 542019956112129021960864034418159813629774771309960518707211349999998372978049 951059731732816096318595024459455346908302642522308253344685035261931188171010 003137838752886587533208381420617177669147303598253490428755468731159562863882 353787593751957781857780532171226806613001927876611195909216420198938095257201 065485863278865936153381827968230301952035301852968995773622599413891249721775 283479131515574857242454150695950829533116861727855889075098381754637464939319 255060400927701671139009848824012858361603563707660104710181942955596198946767 837449448255379774726847104047534646208046684259069491293313677028989152104752 162056966024058038150193511253382430035587640247496473263914199272604269922796 782354781636009341721641219924586315030286182974555706749838505494588586926995 690927210797509302955321165344987202755960236480665499119881834797753566369807 426542527862551818417574672890977772793800081647060016145249192173217214772350 141441973568548161361157352552133475741849468438523323907394143334547762416862 518983569485562099219222184272550254256887671790494601653466804988627232791786 085784383827967976681454100953883786360950680064225125205117392984896084128488 626945604241965285022210661186306744278622039194945047123713786960956364371917 287467764657573962413890865832645995813390478027590099465764078951269468398352 595709825822620522489407726719478268482601476990902640136394437455305068203496
Further discussion
Bet on the millionth digit of π (or Chaitin’s Ω) • The *only* thing random is the choice of digit to bet on • Fairness is about lack of correlation between digit choice
and digit value
Albrecht Cosmology After Planck 9/13 120
3.141592653589793238462643383279502884197169399375105820974944592307816406286 208998628034825342117067982148086513282306647093844609550582231725359408128481 117450284102701938521105559644622948954930381964428810975665933446128475648233 786783165271201909145648566923460348610454326648213393607260249141273724587006 606315588174881520920962829254091715364367892590360011330530548820466521384146 951941511609433057270365759591953092186117381932611793105118548074462379962749 567351885752724891227938183011949129833673362440656643086021394946395224737190 702179860943702770539217176293176752384674818467669405132000568127145263560827 785771342757789609173637178721468440901224953430146549585371050792279689258923 542019956112129021960864034418159813629774771309960518707211349999998372978049 951059731732816096318595024459455346908302642522308253344685035261931188171010 003137838752886587533208381420617177669147303598253490428755468731159562863882 353787593751957781857780532171226806613001927876611195909216420198938095257201 065485863278865936153381827968230301952035301852968995773622599413891249721775 283479131515574857242454150695950829533116861727855889075098381754637464939319 255060400927701671139009848824012858361603563707660104710181942955596198946767 837449448255379774726847104047534646208046684259069491293313677028989152104752 162056966024058038150193511253382430035587640247496473263914199272604269922796 782354781636009341721641219924586315030286182974555706749838505494588586926995 690927210797509302955321165344987202755960236480665499119881834797753566369807 426542527862551818417574672890977772793800081647060016145249192173217214772350 141441973568548161361157352552133475741849468438523323907394143334547762416862 518983569485562099219222184272550254256887671790494601653466804988627232791786 085784383827967976681454100953883786360950680064225125205117392984896084128488 626945604241965285022210661186306744278622039194945047123713786960956364371917 287467764657573962413890865832645995813390478027590099465764078951269468398352 595709825822620522489407726719478268482601476990902640136394437455305068203496
Further discussion
Bet on the millionth digit of π (or Chaitin’s Ω) • The *only* thing random is the choice of digit to bet on • Fairness is about lack of correlation between digit choice
and digit value • Choice of digit comes from Brain (neurons with quantum uncertainties) Random number generator seed time stamp
(when you press enter) brain Etc
Albrecht Cosmology After Planck 9/13 121
3.141592653589793238462643383279502884197169399375105820974944592307816406286 208998628034825342117067982148086513282306647093844609550582231725359408128481 117450284102701938521105559644622948954930381964428810975665933446128475648233 786783165271201909145648566923460348610454326648213393607260249141273724587006 606315588174881520920962829254091715364367892590360011330530548820466521384146 951941511609433057270365759591953092186117381932611793105118548074462379962749 567351885752724891227938183011949129833673362440656643086021394946395224737190 702179860943702770539217176293176752384674818467669405132000568127145263560827 785771342757789609173637178721468440901224953430146549585371050792279689258923 542019956112129021960864034418159813629774771309960518707211349999998372978049 951059731732816096318595024459455346908302642522308253344685035261931188171010 003137838752886587533208381420617177669147303598253490428755468731159562863882 353787593751957781857780532171226806613001927876611195909216420198938095257201 065485863278865936153381827968230301952035301852968995773622599413891249721775 283479131515574857242454150695950829533116861727855889075098381754637464939319 255060400927701671139009848824012858361603563707660104710181942955596198946767 837449448255379774726847104047534646208046684259069491293313677028989152104752 162056966024058038150193511253382430035587640247496473263914199272604269922796 782354781636009341721641219924586315030286182974555706749838505494588586926995 690927210797509302955321165344987202755960236480665499119881834797753566369807 426542527862551818417574672890977772793800081647060016145249192173217214772350 141441973568548161361157352552133475741849468438523323907394143334547762416862 518983569485562099219222184272550254256887671790494601653466804988627232791786 085784383827967976681454100953883786360950680064225125205117392984896084128488 626945604241965285022210661186306744278622039194945047123713786960956364371917 287467764657573962413890865832645995813390478027590099465764078951269468398352 595709825822620522489407726719478268482601476990902640136394437455305068203496
Further discussion
Bet on the millionth digit of π (or Chaitin’s Ω) • The *only* thing random is the choice of digit to bet on • Fairness is about lack of correlation between digit choice
and digit value • Choice of digit comes from Brain (neurons with quantum uncertainties) Random number generator seed time stamp
(when you press enter) brain Etc
• The only randomness in a bet on a digit of π is quantum!
Albrecht Cosmology After Planck 9/13 122
10001000111101010
10001000101001010
10001000101101010
11011000101001010
10001010111101010
Classical Computer: The “computational degrees of freedom” of a classical computer are very classical: Engineered to be well isolated from the quantum fluctuations that are everywhere • Computations are deterministic • “Random” is artificial • Model a classical billiard gas on
a computer: All “random” fluctuations
are determined by (or “readings of”) the initial state.
Further discussion
Std. thinking about classical
probabilities
Albrecht Cosmology After Planck 9/13 123
10001000111101010
10001000101001010
10001000101101010
11011000101001010
10001010111101010
Classical Computer: The “computational degrees of freedom” of a classical computer are very classical: Engineered to be well isolated from the quantum fluctuations that are everywhere • Computations are deterministic • “Random” is artificial • Model a classical billiard gas on
a computer: All “random” fluctuations
are determined by (or “readings of”) the initial state.
Further discussion
Std. thinking about classical
probabilities
Albrecht Cosmology After Planck 9/13 124
Our ideas about probability are like our ideas about color: • Quantum physics gives the correct foundation to
our understanding • Our “classical” intuition predates our knowledge
of QM by a long long time, and works just fine for most things
• Fundamental quantum understanding needed to fix classical misunderstandings in certain cases.
Further discussion
Albrecht Cosmology After Planck 9/13 125
Our ideas about probability are like our ideas about color: • Quantum physics gives the correct foundation to
our understanding • Our “classical” intuition predates our knowledge
of QM by a long long time, and works just fine for most things
• Fundamental quantum understanding needed to fix classical misunderstandings in certain cases.
Further discussion
Albrecht Cosmology After Planck 9/13 126
Our ideas about probability are like our ideas about color: • Quantum physics gives the correct foundation to
our understanding • Our “classical” intuition predates our knowledge
of QM by a long long time, and works just fine for most things
• Fundamental quantum understanding needed to fix classical misunderstandings in certain cases.
Further discussion
Albrecht Cosmology After Planck 9/13 127
3.141592653589793238462643383279502884197169399375105820974944592307816406286 208998628034825342117067982148086513282306647093844609550582231725359408128481 117450284102701938521105559644622948954930381964428810975665933446128475648233 786783165271201909145648566923460348610454326648213393607260249141273724587006 606315588174881520920962829254091715364367892590360011330530548820466521384146 951941511609433057270365759591953092186117381932611793105118548074462379962749 567351885752724891227938183011949129833673362440656643086021394946395224737190 702179860943702770539217176293176752384674818467669405132000568127145263560827 785771342757789609173637178721468440901224953430146549585371050792279689258923 542019956112129021960864034418159813629774771309960518707211349999998372978049 951059731732816096318595024459455346908302642522308253344685035261931188171010 003137838752886587533208381420617177669147303598253490428755468731159562863882 353787593751957781857780532171226806613001927876611195909216420198938095257201 065485863278865936153381827968230301952035301852968995773622599413891249721775 283479131515574857242454150695950829533116861727855889075098381754637464939319 255060400927701671139009848824012858361603563707660104710181942955596198946767 837449448255379774726847104047534646208046684259069491293313677028989152104752 162056966024058038150193511253382430035587640247496473263914199272604269922796 782354781636009341721641219924586315030286182974555706749838505494588586926995 690927210797509302955321165344987202755960236480665499119881834797753566369807 426542527862551818417574672890977772793800081647060016145249192173217214772350 141441973568548161361157352552133475741849468438523323907394143334547762416862 518983569485562099219222184272550254256887671790494601653466804988627232791786 085784383827967976681454100953883786360950680064225125205117392984896084128488 626945604241965285022210661186306744278622039194945047123713786960956364371917 287467764657573962413890865832645995813390478027590099465764078951269468398352 595709825822620522489407726719478268482601476990902640136394437455305068203496
A few final thoughts (Part 3): If you do early universe cosmology, you need to care
about these issues (you could “solve the measure problem” and still have a “classical probability problem”)
If you are suspicious of my claims: Just think of one counterexample.
In any case, I hope you find this mix of ideas as fun as I do!