Confinement versus Bose-Einstein condensation

TL;DR

This paper proposes new lattice simulation methods to study the QCD deconfinement transition at high baryon densities, focusing on Bose-Einstein condensation of diquark fields and fixed baryonic current expectations.

Contribution

It introduces a Lattice Effective Theory with diquark fields and a novel simulation approach fixing baryonic current, enabling exploration of finite density QCD.

Findings

Deconfinement transition modeled as Bose-Einstein condensation of diquarks.

Transition at finite densities appears as a crossover, not first order.

New simulation method avoids sign and overlap problems.

Abstract

The deconfinement phase transition at high baryon densities and low temperatures evades a direct investigation by means of lattice gauge calculations. In order to make this regime of QCD accessible by computer simulations, two proposal are made: (i) A Lattice Effective Theory (LET) is designed which incorporates gluon and diquark fields. The deconfinement transition takes place when the diquark fields undergo Bose-Einstein condensation. (ii) Rather than using eigenstates of the particle number operator, I propose to perform simulations for a fixed expectation value of the baryonic Noether current. This approach changes the view onto the finite density regime, but evades the sign and overlap problems. The latter proposal is exemplified for the LET: Although the transition from the confinement to the condensate phase is first order in the coupling constant space at zero baryon densities, the transition at finite densities appears to be a crossover.