arXiv subjects
Publications and source records attributed to Shailee V. Imrith.
We study the contribution to the primordial curvature perturbation on observational scales generated by the reheating field in massless preheating. To do so we use lattice simulations and a recent extension to the $δN$ formalism. The work demonstrates the functionality of these techniques for calculating the observational signatures of models in which non-perturbative reheating involves a light scalar field.
We revisit the question of how to calculate correlations of the curvature perturbation, $ζ$, using the $δN$ formalism when one cannot employ a truncated Taylor expansion of $N$. This problem arises when one uses lattice simulations to probe the effects of isocurvature modes on models of reheating. Working in real space, we use an expansion in the cross-correlation between fields at different positions, and present simple expressions for observables such as the power spectrum and the reduced bispectrum, $f_{\rm NL}$. These take the same form as those of the usual $δN$ expressions, but with the derivatives of $N$ replaced by non-perturbative $δN$ coefficients. We test the validity of this expansion and argue that our expressions are particularly well suited for use with simulations.