Clustering Fossils from the Early Universe

TL;DR

This paper proposes methods to detect primordial scalar, vector, and tensor fields in galaxy or 21-cm surveys by analyzing deviations in correlation functions, offering new ways to probe early-Universe physics.

Contribution

It introduces optimal estimators for identifying scalar, vector, and tensor imprints in large-scale structure surveys, including parity-violating signals.

Findings

Derived estimators for primordial field components

Analyzed survey sensitivity to different modes

Presented methods to detect parity violation in early Universe

Abstract

Many inflationary theories introduce new scalar, vector, or tensor degrees of freedom that may then affect the generation of primordial density perturbations. Here we show how to search a galaxy (or 21-cm) survey for the imprint of primordial scalar, vector, and tensor fields. These new fields induce local departures to an otherwise statistically isotropic two-point correlation function, or equivalently, nontrivial four-point correlation functions (or trispectra, in Fourier space), that can be decomposed into scalar, vector, and tensor components. We write down the optimal estimators for these various components and show how the sensitivity to these modes depends on the galaxy-survey parameters. New probes of parity-violating early-Universe physics are also presented.