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Inflation : why and how ?

Inflation : why and how ?. Gert Jan Hoeve, December 2012. Problems with the Hot Big Bang. Flatness | Ω -1|<10 16 at nucleosythesis Unwanted relics Horizon problem Homogeneity over parts of space that are presumably not causally correlated . Baryogenesis

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Inflation : why and how ?

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  1. Inflation: whyandhow? Gert Jan Hoeve, December 2012

  2. Problemswith the Hot Big Bang • Flatness • |Ω-1|<1016 at nucleosythesis • Unwantedrelics • Horizon problem • Homogeneity over parts of spacethat are presumablynotcausallycorrelated. • Baryogenesis • Conventionaltheories of symmetrybreaking are insufficientfor the observedammount of baryons

  3. 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

  4. How does cosmicinflationsolve the flatnessproblem? • Ω is pushedtowards 1 duringinflation • ‘Stretching’

  5. Unwantedrelics: magneticmonopoles • Abundant at high temperature • Slow decay

  6. Why do we have a horizon problem? • Cosmic Microwave Background radiationoriginated 500,000 yearsafter the BB. • No causalcorrelationpossible

  7. Inflationsolves the horizon problem: Picture: one minute astronomer

  8. 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

  9. 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

  10. B-violatinginteractions • Standard model: sphalerons • Differenceleptonnumber andbaryonnumerconserved • Example: (u+u+d)+(c+c+s)+(t+t+b)  e++μ++τ+

  11. C and CP violation • B-violatingprocess must outratesymmetricprocess • Both symmetries must beviolated

  12. Thermal non-equilibrium at baryogenesis • Phasetransitionbubbles • Thermal energy gradient at bubbleedge • Local breakdown of time symmetry

  13. How didinflationarise? Scalar field V(φ) causesspontaneoussymmetrybreaking First or second order phasetransition? B. Clauwens , R. Jeanerot, D-term inflationafterspontaneoussymmetrybreaking H. Bohringer

  14. Original model (Guth, 1981) • False/real vacuum • First order phasetransition • Reheatingproblems

  15. 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

  16. Quintessentialscalar field • 5th fundamental force • Continueousdecayingscalar field • Couldexplaininflationanddark energy at the same time! • M. Trodden, Baryogenesisand the new cosmology, 2002

  17. 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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