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SUMMARY:Preheating on curved field-space manifolds - Evangelos Sfakianakis
  (Nikhef)
DTSTART:20191028T130000Z
DTEND:20191028T140000Z
UID:TALK131536@talks.cam.ac.uk
CONTACT:Sadra Jazayeri
DESCRIPTION:I will discuss preheating in multi-field models of inflation w
 ith a curved field-space manifold. In the case of two-field generalization
 s of alpha-attractor models with is a highly curved hyperbolic field-space
  manifold\, analytical progress can be made for preheating using the WKB a
 pproximation and Floquet analysis. I will show the emergence of a simple s
 caling behavior of the Floquet exponents for large values of the field-spa
 ce curvature\, that enables a quick estimation of the reheating efficiency
  for any large value of the field-space curvature. In this regime one can 
 observe and explain universal preheating features that arise for different
  values of the potential steepness. In general preheating is faster for la
 rger negative values of the field-space curvature and steeper potentials. 
 For very highly curved field-space manifolds preheating is essentially ins
 tantaneous.\nIn case of multi-field models with non-minimal couplings\, wh
 ere the field-space in the Einstein frame is highly curved near the origin
 \, I will describe recent lattice simulations that have been used to captu
 re significant nonlinear effects like backreaction and rescattering. I wil
 l show how we can we extract the effective equation of state and typical t
 ime-scales for the onset of thermalization\, quantities that could affect 
 the usual mapping between predictions for primordial perturbation spectra 
 and measurements of anisotropies in the cosmic microwave background radiat
 ion. For large values of the nonminimal coupling constants\,  efficient pa
 rticle production gives rise to nearly instantaneous preheating. Moreover\
 , the strong single-field attractor behavior that was identified for these
  models in linearized analyses remains robust in the full theory\, and in 
 all cases considered the attractor persists until the end of preheating. F
 inally\, I will discuss the implications for Higgs inflation.
LOCATION:CMS\, Pav. B\, CTC Common Room (B1.19) [Potter Room]
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