3,418 research outputs found
On the inflationary massive field with a curved field manifold
Massive fields during inflation provide an interesting opportunity to test
new physics at very high energy scales. Meanwhile in fundamental realizations,
the inflationary field space typically has a curved geometry, which may leave
detectable imprints in primordial observables. In this paper we study an
extension of quasi-single field inflation where the inflaton and the massive
field belong to a curved field manifold. Because of the nontrivial field space
curvature, the massive field here can get significant mass corrections of order
the Hubble scale, thus the quasi-single field predictions on primordial
non-Gaussianity are affected. We derive the same result in an equivalent
approach by using the background effective field theory of inflation, where a
dimension-6 operator is identified to play an important role and its cutoff
scale is associated with the curvature scale of the field space. In addition,
due to the slow-roll evolution of the inflaton, this type of mass correction
has intrinsic time-dependence. Consequently, the running mass modifies the
scaling behaviour in the squeezed limit of the scalar bispectrum, while the
resulting running index measures the curvature of the internal field space.
Therefore the minimal setup of a massive field within curved field space during
inflation may naturally lead to new observational signatures of the field space
geometry.Comment: 23 pages, 5 figures; v2: published version with minor revisions and
references adde
Universality and scaling in multi-field -attractor preheating
We explore preheating in multi-field models of inflation in which the
field-space metric is a highly curved hyperbolic manifold. One broad family of
such models is called -attractors, whose single-field regimes have been
extensively studied in the context of inflation and supergravity. We focus on a
simple two-field generalization of the -model, which has received renewed
attention in the literature. Krajewski et al. concluded, using lattice
simulations, that multi-field effects can dramatically speed-up preheating. We
recover their results and further demonstrate that significant analytical
progress can be made for preheating in these models using the WKB approximation
and Floquet analysis. We find a simple scaling behavior of the Floquet
exponents for large values of the field-space curvature, that enables a quick
estimation of the -model reheating efficiency for any large value of the
field-space curvature. In this regime we further observe and explain universal
preheating features that arise for different values of the potential steepness.
In general preheating is faster for larger negative values of the field-space
curvature and steeper potentials. For very highly curved field-space manifolds
preheating is essentially instantaneous.Comment: 43 pages, 21 figures; v2: published version with analysis extende
- …