Sym-EFT: Accelerating Effective Field Theory of Large Scale Structure with Symbolic Regression

Abstract: We present an emulator suite for the one- and two-loop cold dark matter power spectrum from the Effective Field Theory of Large Scale Structures (EFTofLSS). Specifically, we emulate separately the various contributions to the one- and two-loop parts of the power spectrum, leaving out the possible counterterms which can be added as multiplicative prefactors. By leaving the time-dependence of the counterterms unspecified at the emulation stage, our technique has the advantage of being extremely versatile in fitting any type of counterterm parametrisation to data, or to simulations, without having to change the emulator. We construct our emulators using the method of symbolic regression which results in functions that can be used directly in computer code, while achieving errors of better than $0.5\%$ within the $k$-range of validity of EFT and maintaining ultra-fast computational evaluation of less than $\sim5\times10<sup>{-4}s$ on a single core.