On high-order perturbative calculations at finite density

TL;DR

This paper presents a method to perform high-order perturbative calculations at finite density by reducing complex Feynman integrals to simpler phase space integrals, aiding the study of cold dense QCD.

Contribution

It introduces a novel approach to evaluate fermionic chemical potential integrals as three-dimensional phase space integrals over vacuum on-shell amplitudes.

Findings

Simplifies high-order perturbative calculations at finite density.

Facilitates extension of the Equation of State for cold quark matter.

Provides a framework applicable to thermodynamics of dense QCD.

Abstract

We discuss the prospects of performing high-order perturbative calculations in systems characterized by a vanishing temperature but finite density. In particular, we show that the determination of generic Feynman integrals containing fermionic chemical potentials can be reduced to the evaluation of three-dimensional phase space integrals over vacuum on-shell amplitudes - a result reminiscent of a previously proposed "naive real-time formalism" for vacuum diagrams. Applications of these rules are discussed in the context of the thermodynamics of cold and dense QCD, where it is argued that they facilitate an extension of the Equation of State of cold quark matter to higher perturbative orders.