Finite-volume effects in baryon number fluctuations around the QCD critical endpoint

TL;DR

This study investigates how finite-volume effects influence baryon number fluctuations near the QCD critical endpoint using nonperturbative Dyson--Schwinger equations, revealing volume-dependent variations especially under antiperiodic boundary conditions.

Contribution

It provides a nonperturbative analysis of finite-volume impacts on baryon fluctuations near the QCD critical point using Dyson--Schwinger equations with explicit quark backcoupling.

Findings

Finite volume significantly affects baryon fluctuations with antiperiodic boundary conditions.

Ratios of fluctuations remain nearly invariant despite volume changes.

Results are quantitatively reliable outside the critical scaling region.

Abstract

We present results for the volume dependence of baryon number fluctuations in the vicinity of the (conjectured) critical endpoint of QCD. They are extracted from the nonperturbative quark propagator that is obtained as a solution to a set of truncated Dyson--Schwinger equations of ($2 + 1$)-flavor QCD in Landau gauge, which takes the backcoupling of quarks onto the Yang--Mills sector explicitly into account. This well-studied system predicts a critical endpoint at moderate temperatures and rather large chemical potential. We investigate this system at small and intermediate finite, three-dimensional, cubic volumes and study the resulting impact on baryon number fluctuations and ratios thereof up to fourth order in the region of the critical endpoint. Due to the limitations of our truncation, the results are quantitatively meaningful only outside the critical scaling region of the endpoint. We find that the fluctuations are visibly affected by the finite volume, particularly for antiperiodic boundary conditions, whereas their ratios are practically invariant.