The Quarkyonic Star

TL;DR

This paper explores the quarkyonic matter concept, proposing a unified framework for nuclear matter, quark matter, and color-superconducting states, and discusses implications for neutron star properties.

Contribution

It introduces the quarkyonic scenario as a unified description of dense matter, bridging nuclear, quark, and superconducting phases in neutron stars.

Findings

Proposes a natural interpolation scheme for dense matter states.

Discusses constraints on neutron star mass-radius relations.

Highlights the indistinguishability of different dense matter phases.

Abstract

We discuss theoretical scenarios on crossover between nuclear matter (NM) and quark matter (QM). We classify various possibilities into three major scenarios according to the onset of diquark degrees of freedom that characterizes color-superconducting (CSC) states. In the conventional scenario NM occurs at the liquid-gas (or liquid-vacuum at zero temperature) phase transition and QM occurs next, after which CSC eventually appears. With the effect of strong correlation, the BEC-BCS scenario implies that CSC occurs next to NM and QM comes last in the BCS regime. We adopt the quarkyonic scenario in which NM, QM, and CSC are theoretically indistinguishable and thus these names refer to not distinct states but relevant descriptions of the same physical system. Based on this idea we propose a natural scheme to interpolate NM near normal nuclear density and CSC with vector coupling at high baryon density. We finally discuss the mass-radius relation of the neutron star and constraints on parameters in the proposed scheme.