Small Bits of Cold Dense Matter

TL;DR

This paper explores the properties of cold dense QCD matter by studying small baryonic systems with periodic boundary conditions, comparing nucleon and quark models, and suggesting lattice QCD as a feasible approach for such investigations.

Contribution

It demonstrates that small systems reveal nuclear features and are suitable for lattice QCD studies, advancing understanding of neutron star matter at high baryon density.

Findings

Nuclear shell structure and pairing emerge in small baryonic systems.

Small systems are more accessible to lattice QCD due to reduced sign problem.

Comparison between nucleon and quark models informs the cold dense equation of state.

Abstract

The behavior of QCD at high baryon density and low temperature is crucial to understanding the properties of neutron stars and gravitational waves emitted during their mergers. In this paper we study small systems of baryons in periodic boundary conditions to probe the properties of QCD at high baryon density. By comparing calculations based on nucleon degrees of freedom to simple quark models we show that specific features of the nuclear spectrum, including shell structure and nucleon pairing, emerge if nucleons are the primary degrees of freedom. Very small systems should also be amenable to studies in lattice QCD, unlike larger systems where the fermion sign problem is much more severe. Through comparisons of lattice QCD and nuclear calculations it should be possible to gain, at at least a semi-quantitative level, more understanding of the cold dense equation of state as probed in neutron stars.