Multiverse from a particle physicist’s perspective Taizan Watari (Univ. of Tokyo) KEK PH07 Mar.03...
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Transcript of Multiverse from a particle physicist’s perspective Taizan Watari (Univ. of Tokyo) KEK PH07 Mar.03...
MultiverseMultiversefrom a particle physicist’s from a particle physicist’s
perspectiveperspective
Taizan Watari (Univ. of Tokyo)Taizan Watari (Univ. of Tokyo)
KEK PH07 Mar.03 2007KEK PH07 Mar.03 2007
review + ph/0608121 th/0506235 (w/ B. Feldstein and L. Hall )
Why is the CC Why is the CC unnaturally small?unnaturally small?
The CC may take different values in The CC may take different values in different parts of the “universe.” ---- different parts of the “universe.” ---- multiversemultiverse
Quantum process of creation of space-Quantum process of creation of space-time determines weight factor time determines weight factor which is sharply peaked at which is sharply peaked at
But in nature, But in nature,
10 ,e LL :
0.L ;
0.L ¹
Baum ’83, Hawking ‘84
Why is the CC small Why is the CC small but but non-zeronon-zero??
The CC may take different values in The CC may take different values in different parts of the “universe.” ---- different parts of the “universe.” ---- multiversemultiverse
Only in vacua with small enough CC, Only in vacua with small enough CC, galaxies are formed. galaxies are formed.
Weinberg ‘87
Density perturbations grow during Density perturbations grow during matter dominance, but not during matter dominance, but not during radiation, curvature or CC dominance.radiation, curvature or CC dominance.
As As Gravitational bound systems are Gravitational bound systems are formed only whenformed only when
Larger CC is more natural, but too large Larger CC is more natural, but too large CC is not observed anyway. CC is not observed anyway.
The most natural observed value of the The most natural observed value of the CCCC
(roughly) (roughly) explains explains the small but non-zero value of the CC in the small but non-zero value of the CC in this universe.this universe.
(1),Od® 3; ; .DM eq DM eqr r d®
3;[ ].CC DM eqr r d£
3;[ ]CC DM eqr r d»
Plan of the talkPlan of the talk
Introduction: the CC problem.Introduction: the CC problem. Theoretical frameworkTheoretical framework Bottom-up approachBottom-up approach
Living on the edgeLiving on the edge Ex.1: Scanning inflaton potentialEx.1: Scanning inflaton potential Ex.2: Scanning Higgs potentialEx.2: Scanning Higgs potential
Big remaining issuesBig remaining issues SummarySummary
theoretical theoretical frameworkframework
Variety of vacua Variety of vacua (theories) Landscape of (theories) Landscape of
vacuavacua Parameters: maybe field vev at potential Parameters: maybe field vev at potential
minimumminimum e.g. strong CP phase in Peccei-Quinn mechanism e.g. strong CP phase in Peccei-Quinn mechanism
Fundamental theory may have multiple vacuaFundamental theory may have multiple vacua motivated by the CC problemmotivated by the CC problem
Superstring theory so far Superstring theory so far
admits enormous number admits enormous number
of vacua.of vacua.
Probability DistributionProbability Distribution
Landscape of vacua, density of states
Cosmological evolution of multiverse
Environmental selection factor
( ) .i iP x dx
( ) ( ) .i i iA x P x dx
poorly known
topics of hot debate (for more than 20 years)
often difficult to quantify
In principle, and follow from theory. ix ij i jx xs d d=
Vilenkin ‘95
bottom-up bottom-up approachapproach
Living on the EdgeLiving on the Edge
Typical values of observables do not depend on the detailed assumptions of ( ) .i iP x dx
tends to be on the edge of the window; majority do not live in the heaven, though not in the hell.
The edge of the window can be studied only with the standard model.
Environmental selection (usually) depends only on low-energy physics.
ix
Ex.1: Scanning inflaton Ex.1: Scanning inflaton potentialpotential
fine tuning problem (eta fine tuning problem (eta problem) to achieve problem) to achieve in slow-roll inflation in slow-roll inflation
scanning inflaton potential in a scanning inflaton potential in a multiverse: Potential may be multiverse: Potential may be flat enough by chance, somewhere in flat enough by chance, somewhere in the multiverse.the multiverse.
1( )60O60Hdt
e eò :
Freivogel, Kleban, Martinez, Susskind ‘05
Direct transitionDirect transition to a Standard-Model to a Standard-Model vacuum results in an open universe: vacuum results in an open universe: no no str. formation.str. formation.
Majority of observers live in vacua Majority of observers live in vacua associated w/ inflaton potentials barely associated w/ inflaton potentials barely flat enough to allow galaxy formation.flat enough to allow galaxy formation.
Our universe does not have to be flat at Our universe does not have to be flat at 3000 Mpc scale. is expected 3000 Mpc scale. is expected to be a little smaller than 1 (a slightly to be a little smaller than 1 (a slightly open universe).open universe).
M LW +W
large inflaton massflat inflaton potential
Ex.2: Scanning Higgs Ex.2: Scanning Higgs PotentialPotential
24 2 4( ) .
2 4V H H H
m l=L - +
4 :L the cosmological constant
2 2 / :v m l= The Higgs VEV sets the weak scale.
/QCD vL /PM vand are important parameters of nuclear and astrophysics.
The other independent combination, or does not seem to be an “anthropic” parameter.
l 2 22Hm vl=
Agrawal Barr Donoghue Seckel ‘97, Graesser Salem ‘06
1-Loop Renormalized 1-Loop Renormalized PotentialPotential
24 2 4( )
( ) .2 4
HV H H H
m l=L - +
Vacuum DecayVacuum Decay
Negative quartic coupling up-side-down potential
vacuum tunneling.
284 3| ( )|
0[ ] max [ ( )] max[ ].SM
M
M MM M e
pll
-
<L <LG » G =
Vacuum tunneling rate
Sher; Casas Espinosa Quiros; Ishidori Ridolfi Strumia
Living on the Edge Living on the Edge of Vacuum Stabilityof Vacuum Stability
[time t] x [volume of the past light cone (ct)^3]
This environmental selection factor does not require much knowledge in astronomy or nuclear physics.
If the a priori distribution is weighted toward smaller (negative) value, typical observers do live on the edge of the vacuum meta-stability.
0 0( )P dl l
40[ ] 1tlG £
Higgs Boson Mass Higgs Boson Mass PredictionPrediction
[ The last term comes from higher orders in the threshold corrections etc.]
The environmental selection provides a very hard cut-off.
for
Feldstein Hall TW ‘06
cl | |cp
l
4[ ]te l- G l
big remaining big remaining issuesissues
Cosmological Weight and Cosmological Weight and InflationInflation
# of observers the volume of # of observers the volume of universe??universe?? The weight factor depends exponentially on The weight factor depends exponentially on
inflaton parameters.inflaton parameters.
Eternal inflation---inflation goes on Eternal inflation---inflation goes on forever.forever. How to compare How to compare
infinite volumesinfinite volumes two volumes that are two volumes that are
causally disconnected causally disconnected
µ
inflaton massflat potential
What is ??dRunaway problem.
Feldstein Hall TW ’05Garriga Vilenkin ‘05
Linde Garcia-Bellido Garriga Vilenkin Guth ...
Multi-parameter Multi-parameter Scanning IScanning I
The CC upper boundThe CC upper bound What if either or is scanned??What if either or is scanned??
Too large or too tightly Too large or too tightly packed galaxies.packed galaxies.
What if all of are scanned What if all of are scanned simultaneously??simultaneously??
3;[ ].CC DM eqr r d£
DMs
r d
DMs
r d
Graeser Hsu Jenkins Wise ‘04
Tegmark Rees ‘97
( , , , )DMCC Bs
rr h dTegmark Aguirre Rees Wilczek ‘05
very complicated to perform a full analysis
Multi-parameter Multi-parameter scanning IIscanning II
An anthropic solution to the hierarchy An anthropic solution to the hierarchy problem using nuclear physics (Agrawal problem using nuclear physics (Agrawal et.al. ‘97 ) is actually a constraint on et.al. ‘97 ) is actually a constraint on . . What if is scanned, while is kept What if is scanned, while is kept
fixed?? fixed??
Is the limit on still there when all Is the limit on still there when all the low-energy parameters are the low-energy parameters are scanned??scanned??
QCD
vL
P
vM QCD
vL
Graesser Salem ‘06
QCD
vL
( , , , , , )s QED u d e Fm m m Ga a
Astrophysics and nuclear physics are VERY complicated.
the CC Problemthe CC Problem a flat inflaton potentiala flat inflaton potential density perturbationsdensity perturbations dark matter abundancedark matter abundance baryon asymmetrybaryon asymmetry weak / Planck hierarchyweak / Planck hierarchy Weinberg angleWeinberg angle Higgs boson massHiggs boson mass q, l Yukawa couplingsq, l Yukawa couplings
Symmetry Statistics + Selection Fundamental TheoryCosmological Evolution
Universe
Multiverse
( , , , , ,...)C u d e Fm m m G
o stable WIMPstable WIMPo lepton Yukawalepton Yukawao SUSY etc.SUSY etc.o SUSY GUTSUSY GUT
o D-term D-term potentialpotential
o flavor flavor symmetrysymmetry
o Weinberg ’87Weinberg ’87o flat spacious flat spacious
univ.univ.o Tegmark-Rees Tegmark-Rees
’97’97o str. formationstr. formationo str. formation str. formation
(all (all compatible??)compatible??)
o sensitivesensitive
o sensitivesensitiveo vacuum vacuum
stability stability
[ not a winner-take-all game ]
Higgs Boson Mass Higgs Boson Mass Prediction II:Prediction II:
Here, an instantaneous reheating after inflation is assumed.
If not, the highest temperature of thermal plasma after inflation is higher than the reheating temperature, the analysis and predictionare slightly different.
Top Quark Mass Top Quark Mass PredictionPrediction