BEC-BCS Crossover and the EoS of Strongly Interacting Systems

TL;DR

This paper investigates the BEC-BCS crossover in strongly interacting quark systems, emphasizing the importance of diquark-diquark repulsion for maintaining positive pressure and exploring implications for compact star physics and magnetic field effects.

Contribution

It introduces a self-consistent treatment of diquark-diquark repulsion, identifying a critical coupling that stabilizes the system and prevents collapse at zero temperature.

Findings

Diquark-diquark repulsion prevents collapse into a pressureless state.

A critical coupling value stabilizes the diquark gas at zero temperature.

Magnetic fields influence the BEC-BCS crossover behavior.

Abstract

We show that at sufficiently strong coupling, quarks form a BEC system that does not collapse into a pressureless gas at zero temperature only if the diquark-diquark repulsion is self-consistently taken into account. It is found that there is a critical value of the coupling constant of the diquark-diquark interaction beyond which the tendency at zero temperature of the strongly interacting diquark gas to condense into the system ground state with zero momentum is compensated by the repulsion between diquarks so keeping a positive pressure with no significant variation along the whole strongly interacting region. We discuss possible implications of the diquark-diquark interaction for the astrophysics of compact stars. Also we analyze the effect of a strong magnetic field for the BEC-BCS crossover.