Spectroscopy in finite density lattice field theory: An exploratory study in the relativistic Bose gas

TL;DR

This study investigates lattice spectroscopy in the relativistic Bose gas at finite density, demonstrating that the particle mass remains constant below the condensation threshold, consistent with the Silver Blaze phenomenon.

Contribution

It introduces a dual flux representation and Monte Carlo simulation method to analyze spectral properties at finite density in lattice field theory.

Findings

Masses are mu-independent below the critical chemical potential.

Forward and backward propagator exponents agree after subtraction.

The Silver Blaze scenario is confirmed in the relativistic Bose gas.

Abstract

We analyze 2-point functions in the relativistic Bose gas on the lattice, i.e., a charged scalar phi-4 field with chemical potential mu. Using a generalized worm algorithm we perform a Monte Carlo simulation in a dual representation in terms of fluxes where the complex action problem is overcome. We explore various aspects of lattice spectroscopy at finite density and zero temperature, such as the asymmetry of forward and backward propagation in time and the transition into the condensed phase. It is shown that after a suitable subtraction the exponents for forward and backward propagation are independent of mu and agree with the mass obtained from the propagator at mu = 0. This holds for mu < mu_c and shows that below the condensation transition the mass is independent of mu as expected from the Silver Blaze scenario.