GLASS: Generator for Large Scale Structure

TL;DR

GLASS is a new simulation code that efficiently generates realistic, high-resolution galaxy survey data including matter, galaxies, and weak lensing signals, useful for cosmological analysis.

Contribution

It introduces novel techniques for transforming Gaussian fields, iterative line-of-sight integration, and flexible galaxy modeling, enabling high-precision, resource-efficient simulations.

Findings

Produces simulations with percent-level accuracy in two-point statistics

Enables validation and inference limited only by input knowledge

Operates efficiently on standard hardware

Abstract

We present GLASS, the Generator for Large Scale Structure, a new code for the simulation of galaxy surveys for cosmology, which iteratively builds a light cone with matter, galaxies, and weak gravitational lensing signals as a sequence of nested shells. This allows us to create deep and realistic simulations of galaxy surveys at high angular resolution on standard computer hardware and with low resource consumption. GLASS also introduces a new technique to generate transformations of Gaussian random fields (including lognormal) to essentially arbitrary precision, an iterative line-of-sight integration over matter shells to obtain weak lensing fields, and flexible modelling of the galaxies sector. We demonstrate that GLASS readily produces simulated data sets with per cent-level accurate two-point statistics of galaxy clustering and weak lensing, thus enabling simulation-based validation and inference that is limited only by our current knowledge of the input matter and galaxy properties.