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Inflation : why and how ?PowerPoint Presentation

Inflation : why and how ?

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### Inflation: whyandhow?

Gert Jan Hoeve, December 2012

Problemswith the Hot Big Bang Unwantedrelics Horizon problem Baryogenesis

- Flatness
- |Ω-1|<1016 at nucleosythesis

- Homogeneity over parts of spacethat are presumablynotcausallycorrelated.

- Conventionaltheories of symmetrybreaking are insufficientfor the observedammount of baryons

The solution: inflation

d2a/dt2 >> 0

or equivalently,

-(dH/dt)/H2 >> 1

Between Planck time (10-43) andGUT decoupling (10-35)

Alan Guth, 1981

Picture: Wikipedia

How does cosmicinflationsolve the flatnessproblem?

- Ω is pushedtowards 1 duringinflation
- ‘Stretching’

Unwantedrelics: magneticmonopoles

- Abundant at high temperature
- Slow decay

Why do we have a horizon problem?

- Cosmic Microwave Background radiationoriginated 500,000 yearsafter the BB.
- No causalcorrelationpossible

Inflationsolves the horizon problem:

Picture: one minute astronomer

How muchinflation do we need?

Inflationends at t0 = 10-35 s, we are at t1 = 1017 s

In radiationdominateduniverse |Ω-1|proportional to time

|Ωnow-1| ≤ 10-2 |ΩGUT-1|≤ 10-54

Recall|Ω-1|=|k|/(Ha)2

Duringinflation H=constant, so|Ω-1|proportional to 1/a2

Total expansion > ~ 1027

Baryogenesis

- Three conditions (Sakharov’sconditions)
- Baryon numberviolatinginteractions
- obvious

- C violationand CP violation
- Becauseany B-violatinginteractionwouldbemirroredby a complementaryinteraction

- Thermal non-equilibrium (or CPT violation)
- Otherwise the backwardsreactionwouldbeequilly strong

- Baryon numberviolatinginteractions

B-violatinginteractions

- Standard model:
sphalerons

- Differenceleptonnumber
andbaryonnumerconserved

- Example:
(u+u+d)+(c+c+s)+(t+t+b) e++μ++τ+

C and CP violation

- B-violatingprocess must outratesymmetricprocess
- Both symmetries
must beviolated

Thermal non-equilibrium at baryogenesis

- Phasetransitionbubbles
- Thermal energy gradient at bubbleedge
- Local breakdown of time symmetry

How didinflationarise?

Scalar field V(φ) causesspontaneoussymmetrybreaking

First or second order phasetransition?

B. Clauwens , R. Jeanerot, D-term inflationafterspontaneoussymmetrybreaking

H. Bohringer

Original model (Guth, 1981)

- False/real vacuum
- First order phasetransition
- Reheatingproblems

Slow-rollinflation (Linde, 1982)

- d2φ/dt2 + 3H dφ/dt = -dV(φ)/dφ
- Friedman H2 = (1/2 dφ/dt+V(φ))/3 –k/a2
- Inflationdecays as slopeincreases
- H=(da/dt)/a

Quintessentialscalar field

- 5th fundamental force
- Continueousdecayingscalar field
- Couldexplaininflationanddark energy at the same time!

- M. Trodden, Baryogenesisand the new cosmology, 2002

Conclusion

Cosmologicalinflation is a viable hypothesis, but in desperate need of a more solid foundation (and experimental confirmation) from the realm of particle physics.

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