Particle Physics and Cosmology

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Particle Physicsand Cosmology

• Baryon asymmetry

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Boltzmann equation in terms of cross section
.
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dimensionless inverse temperature
m particle mass
small x particle is relativistic
xlt3 large x particle is non-relativistic
xgt3
dimensionless time variable in units of particle
mass m
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particle number per entropy
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cold relic fraction
not necessarily order one !
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cold relic abundance ,mass and cross section
(m,sA)
m
inversely proportional to cross section , plus
logarithmic dependence of xf
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baryon relics in baryon symmetric Universe
observed Y ? 10 -10
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baryons the matter of stars and humans
Ob 0.045
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Abundancies of primordial light elements from
nucleosynthesis
A.Coc
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primordial abundances for three GUT models
present observations 1s
He
D
Li
T.Dent, S.Stern,
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present baryon number
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anti-baryons in baryon asymmetric Universe
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conserved baryon asymmetry
no baryon number violating processes in standard
model of particle physics at energy below 1
GeV baryon asymmetry must exist at T 1 GeV
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high temperature baryon problem
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baryon number violation in standard model

• baryon number is global symmetry of interactions
  in the standard model
• violated by quantum anomaly ( no anomalies
  possible for local symmetries corresponding
  charge , like electric charge , exactly conserved
  )
• sphaleron processes generate strong baryon number
  violating processes at temperatures above 100-200
  GeV

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baryon number violation in standard model
no chemical potential for baryon number
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thermal equilibrium in absence of chemical
potential
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baryogenesis
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Sakharovs conditions forbaryogenesis

1. baryon number violation interactions
2. charge conjugation violating interactions
3. CP violating interactions
4. non equilibrium process

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baryon number violating processin Grand Unified
Theories ( GUT )
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baryon number violating processin Grand Unified
Theories ( GUT )
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not good enough B asymmetry will be washed out
later by sphaleron processes no B-L asymmetry
is produced
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leptogenesis or late baryogenesis
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leptogenesis

• B L is conserved quantum number in
• standard model
• sphaleron processes transmute lepton asymmetry
  into baryon asymmetry
• a fraction of primordial B-L asymmetry appears as
  baryon asymmetry
• primordial asymmetry protected from wash out by
  sphaleron processes

( B-L )
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leptogenesis

• non equilibrium decay of heavy neutrinos
• non equilibrium production after inflation
  during entropy production of the Universe

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baryogenesis during electroweak phase transition
?
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Sakharovs conditions forbaryogenesis during
electroweak phase transition

1. baryon number violation interactions ?
2. charge conjugation violating interactions ?
3. CP violating interactions ?
4. non equilibrium process ?

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cosmological phase transitions
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cosmological phase transitions
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first order cosmological phase transitions
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chaos in the Universe
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baryogenesis during electroweak phase transition

• strongly first order electroweak phase transition
  can generate baryon asymmetry if CP violation is
  sufficiently strong
• no efficient baryogenesis for weak first order
  phase transition, second order phase transition
  or crossover
• presumably too little CP violation in SM ( not
  definitely settled )

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electroweak phase transition in standard model
is crossover !
perhaps strong first order transition in
supersymmetric extensions of standard model
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standard model of particle physics and cosmology

• no candidate for dark matter
• no baryon asymmetry
• no massive neutrinos

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standard model of particle physics and cosmology

• prediction
• present Universe consists of
• photons and
• massless neutrinos