Accelerating cosmological inference with Gaussian processes and neural networks -- an application to LSST Y1 weak lensing and galaxy clustering

TL;DR

This paper introduces a method combining Gaussian processes and neural networks to create emulators that significantly speed up cosmological likelihood analyses, enabling rapid exploration of survey strategies and systematic effects in large-scale structure studies.

Contribution

The paper presents a novel emulator framework that iteratively learns high-dimensional data vectors, achieving an order of magnitude faster cosmological inference for LSST-Y1 data.

Findings

Achieves high-fidelity posterior contours with 10x speed-up.

Enables rapid impact studies, reducing MCMC runs to about 5 minutes.

Facilitates efficient exploration of survey and systematic effects.

Abstract

Studying the impact of systematic effects, optimizing survey strategies, assessing tensions between different probes and exploring synergies of different data sets require a large number of simulated likelihood analyses, each of which cost thousands of CPU hours. In this paper, we present a method to accelerate cosmological inference using emulators based on Gaussian process regression and neural networks. We iteratively acquire training samples in regions of high posterior probability which enables accurate emulation of data vectors even in high dimensional parameter spaces. We showcase the performance of our emulator with a simulated 3x2 point analysis of LSST-Y1 with realistic theoretical and systematics modelling. We show that our emulator leads to high-fidelity posterior contours, with an order of magnitude speed-up. Most importantly, the trained emulator can be re-used for extremely fast impact and optimization studies. We demonstrate this feature by studying baryonic physics effects in LSST-Y1 3x2 point analyses where each one of our MCMC runs takes approximately 5 minutes. This technique enables future cosmological analyses to map out the science return as a function of analysis choices and survey strategy.