From Heavy-Ion Collisions to Compact Stars: Equation of State and Relevance of the System Size

TL;DR

This paper reviews state-of-the-art methods for computing conserved charge fluctuations in QCD, compares lattice results, and explores finite size effects in heavy-ion collisions and their implications for the equation of state and system size relevance.

Contribution

It introduces advanced computational techniques for baryon number fluctuations, compares lattice QCD results, and investigates finite size effects in relativistic quantum systems relevant to heavy-ion collisions.

Findings

Lattice QCD results for number susceptibilities align with theoretical predictions.

Finite size effects significantly influence thermodynamic properties at high temperatures.

Preliminary results suggest system size impacts the speed of sound in relativistic quantum systems.

Abstract

In this article, we start by presenting state-of-the-art methods allowing us to compute moments related to the globally conserved baryon number, by means of first principle resummed perturbative frameworks. We focus on such quantities for they convey important properties of the finite temperature and density equation of state, being particularly sensitive to changes in the degrees of freedom across the quark-hadron phase transition. We thus present various number susceptibilities along with the corresponding results as obtained by lattice quantum chromodynamics collaborations, and comment on their comparison. Next, omitting the importance of coupling corrections and considering a zero-density toy model for the sake of argument, we focus on corrections due to the small size of heavy-ion collision systems, by means of spatial compactifications. Briefly motivating the relevance of finite size effects in heavy-ion physics, in opposition to the compact star physics, we present a few preliminary thermodynamic results together with the speed of sound for certain finite size relativistic quantum systems at very high temperature.