STOLAS: STOchastic LAttice Simulation of cosmic inflation

TL;DR

STOLAS is a C++ simulation package for modeling cosmic inflation on a lattice, capable of directly mapping curvature perturbations and estimating primordial black hole abundance non-perturbatively.

Contribution

It introduces a novel lattice simulation tool for cosmic inflation that directly computes curvature perturbations and applies importance sampling for primordial black hole predictions.

Findings

Consistent with standard perturbation theory in toy models

Successfully samples primordial black hole abundance non-perturbatively

Provides a publicly available simulation package

Abstract

We develop a C++ package of the STOchastic LAttice Simulation (STOLAS) of cosmic inflation. It performs the numerical lattice simulation in the application of the stochastic-$\delta N$ formalism. STOLAS can directly compute the three-dimensional map of the observable curvature perturbation without estimating its statistical properties. In its application to two toy models of inflation, chaotic inflation and Starobinsky's linear-potential inflation, we confirm that STOLAS is well-consistent with the standard perturbation theory. Furthermore, by introducing the importance sampling technique, we have success in numerically sampling the current abundance of primordial black holes in a non-perturbative way. The package is available at https://github.com/STOchasticLAtticeSimulation/STOLAS_dist.