Flux Correlators and Semiclassics

TL;DR

This paper analyzes flux correlators in conformal field theories with large global charge, adapting semiclassical EFT methods to Lorentzian observables and exploring their validity and corrections.

Contribution

It extends the semiclassical EFT approach for flux correlators to Lorentzian signatures and examines subleading corrections, including a weakly coupled realization at the Wilson-Fisher fixed point.

Findings

Leading large charge behavior of flux correlators computed.

Validity regime of the EFT for Lorentzian observables discussed.

Subleading corrections systematically analyzed at the Wilson-Fisher fixed point.

Abstract

We consider correlators for the flux of energy and charge in the background of operators with large global $U(1)$ charge in conformal field theory (CFT). It has recently been shown that the corresponding Euclidean correlators generically admit a semiclassical description in terms of the effective field theory (EFT) for a conformal superfluid. We adapt the semiclassical description to Lorentzian observables and compute the leading large charge behavior of the flux correlators in general $U(1)$ symmetric CFTs. We discuss the regime of validity of the large charge EFT for these Lorentzian observables and the subtleties in extending the EFT approach to subleading corrections. We also consider the Wilson-Fisher fixed point in $d=4-\epsilon$ dimensions, which offers a specific weakly coupled realization of the general setup, where the subleading corrections can be systematically computed without relying on an EFT.