The sound speed and core of massive compact stars: A manifestation of hadron-quark duality

TL;DR

This paper proposes a topological approach to describe the cores of massive compact stars, revealing emergent symmetries and a pseudo-conformal sound velocity, suggesting a form of hadron-quark duality without explicit quark degrees of freedom.

Contribution

It introduces a topology change framework that captures hadron-quark duality and emergent symmetries in dense nuclear matter, linking nuclear correlations to QCD properties.

Findings

Pseudo-conformal sound velocity of about 1/3 at densities above 3n0.

Emergent hidden symmetries from nuclear correlations.

Potential link between g_A quenching and the onset of pseudo-conformal behavior.

Abstract

When baryon-quark continuity is formulated in terms of a topology change without invoking "explicit " QCD degrees of freedom at a density higher than twice the nuclear matter density $n_0$ the core of massive compact stars can be described in terms of fractionally charged particles, behaving neither like pure baryons nor deconfined quarks. Hidden symmetries, both local gauge and pseudo-conformal (or broken scale), lead to the pseudo-conformal (PC) sound velocity $v_{pcs}^2/c^2\approx 1/3$ at $\gsim 3n_0$ in compact stars. We argue these symmetries are "emergent" from strong nuclear correlations and conjecture that they reflect hidden symmetries in QCD proper exposed by nuclear correlations. We establish a possible link between the quenching of $g_A$ in superallowed Gamow-Teller transitions in nuclei and the precocious onset at $n\gsim 3n_0$ of the PC sound velocity predicted at the dilaton limit fixed point. We propose that bringing in explicit quark degrees of freedom as is done in terms of the "quarkyonic" and other hybrid hadron-quark structure and our topology-change strategy represent the "hadron-quark duality" formulated in terms of the Cheshire-Cat mechanism~\cite{CC} for the smooth cross-over between hadrons and quarks. Confrontation with currently available experimental observations is discussed to support this notion.