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Reheating of the Universe after Inflation with ffR Gravity: Spontaneous Decay of Inflatons to Bosons, Fermions, and Gaug

Why Study Reheating?. The universe was left cold and empty after inflation.But, we need a hot Big Bang cosmology. The universe must reheat after inflation.Successful inflation must transfer energy in inflaton to radiation, and heat the universe to at least ~1 MeV for successful nucleosynthesis.

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Reheating of the Universe after Inflation with ffR Gravity: Spontaneous Decay of Inflatons to Bosons, Fermions, and Gaug

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    1. Reheating of the Universe after Inflation with f(f)R Gravity: Spontaneous Decay of Inflatons to Bosons, Fermions, and Gauge Bosons Eiichiro Komatsu & Yuki Watanabe University of Texas at Austin Caltech High Energy Physics Seminar, March 28, 2007

    3. Standard Picture

    4. Perturbative Reheating Dolgov & Linde (1982); Abbott, Farhi & Wise (1982); Albrecht et al. (1982)

    5. Reheating Temperature from Energetics

    6. Fine-tuning Problem?

    7. What are coupling constants? Problem: arbitrariness of the nature of inflaton fields

    8. Conventional Einstein gravity during inflation

    9. Modifying Einstein gravity during inflation

    10. Field equations: GR

    11. Field equations: f(?)R gravity

    12. New decay channel through “scalar gravity waves”

    13. Spontaneous emergence of Yukawa interaction: analog of spontaneous symmetry breaking

    15. Magnitude of Yukawa coupling For f(?)=?????g=?(v/Mpl)(m/Mpl) Natural to obtain g~10-7 for e.g., m~10-7 Mpl The induced Yukawa coupling vanishes for massless fermions: conformal invariance of massless fermions. Massless, minimally-coupled scalar fields are not conformally invariant. Therefore, the three-legged interaction does not vanish even for massless scalar fields:

    16. The Results So Far… After inflation with f(?)R gravity, inflatons decay spontaneously into: Massive fermions, Massive scalar bosons, or Massless scalar bosons with non-conformal coupling. The smallness of coupling can be explained naturally. Inflaton decay is “built-in” and the coupling constrants can be calculated explicitly from a single function, f(?). Rates of decay to fermions and bosons are related. This mechanism allows inflatons to decay into any fields that are not conformally coupled. Other possibilities?

    17. Breaking of conformal invariance by anomaly

    18. Conformal anomaly: Lowest order decay channel to massless gauge fields

    19. Decay Width Summary

    20. Constraint on f(f)R gravity models from reheating

    21. Connection to Supergravity? Similar effects have been pointed out by Endo, Takahashi and Yanagida (2006; 2007) in the context of supergravity Inflatons decay into any fields even if inflatons are not coupled directly with these fields in the superpotential A correspondence may be made as f(?)R gravity <-> Kahler potential Conformal anomaly <-> Super-Weyl anomaly Our model is simpler and does not require explicit use of supergravity -- hence more general. It may also give physical (rather than mathematical) insight into their effects.

    22. Conclusions A natural mechanism for reheating after inflation with f(f)R gravity: Why natural? Inflaton quanta decay spontaneously into any matter fields (spin-0, ½, 1) without explicit interactions in the original Lagrangian Conformal invariance must be broken at the tree-level or by loops Reheating spontaneously occurs in any theories with f(f)R gravity Predictability All the decay widths are related through a single function, f(f). A constraint on f(f) from the reheat temperature can be found A possible limit on the reheat temperature can constrain the form of f(f), or vice versa. These constraints on f(f) are totally independent of the other constraints from inflation and density fluctuations Further Study… Preheating? F(?,R) gravity?

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