Quark-cluster Stars: the structure

TL;DR

This paper proposes the concept of quark-cluster stars as a realistic model for pulsars, suggesting they are composed of clustered quark matter, which could explain observational data and bridge gaps in understanding dense matter physics.

Contribution

It introduces the quark-cluster star model, emphasizing clustering of quarks due to strong coupling, and discusses its potential to reconcile theoretical and observational aspects of pulsars.

Findings

Quark-cluster stars could be composed of nearly equal numbers of up, down, and strange quarks.

Clustering may result from strong coupling between quarks inside compact stars.

The model offers a new perspective on the state of supra-nuclear matter in pulsars.

Abstract

The nature of pulsar-like compact stars is still in controversy although the first pulsar was found more than 40 years ago. Generally speaking, conventional neutron stars and non-mainstream quark stars are two types of models to describe the inner structure of pulsars, with the former composed mainly of hadrons and the latter of a peculiar kind of matter whose state equation should be understood in the level of quarks rather than hadrons. To construct a more realistic model from both theoretical and observational points of view, we conjecture that pulsars could be "quark-cluster stars" which are composed of quark-clusters with almost equal numbers of up, down and strange quarks. Clustering quark matter could be the result of strong coupling between quarks inside realistic compact stars. The lightest quark clusters could be of H-dibaryons, while quark clusters could also be heavier with more quarks. Being essentially related to the non-perturbative quantum-chromo dynamics (QCD), the state of supra-nuclear condensed matter is really difficult to obtain strictly by only theoretical QCD-calculations, and we expect, nevertheless, that astrophysical observations could help us to have a final solution.