The Role of Vector Mesons for Emergent Scale-Chiral Symmetry in Nuclear Interactions

TL;DR

This paper explores how emergent scale and gauge symmetries involving vector mesons influence nuclear interactions at high density, revealing phenomena relevant for neutron stars and involving topology change, parity doubling, and symmetry energy stiffening.

Contribution

It introduces a scale-invariant hidden local symmetric Lagrangian incorporating vector mesons and a dilaton, revealing emergent symmetries and topology change effects at high density.

Findings

Emergent scale and gauge symmetries above nuclear saturation density.

Topology change at a critical density affects nuclear structure.

Vector meson properties and symmetry energy behavior are significantly altered.

Abstract

When a light scalar dilaton $\sigma$ and the light-quark vector mesons $V=(\rho,\omega)$ are incorporated into an effective scale-invariant hidden local symmetric (sHLS) Lagrangian, scale symmetry for $\sigma$ and local gauge symmetry for $V$, both invisible in QCD in the vacuum, arise as emergent symmetries at a density above $n_{1/2}\sim 2n_0$, a phenomenon highly relevant for massive compact stars, hitherto unobserved in standard chiral pertubative approaches. What takes place involves a topology change at $n_{1/2}$, and as the density increases beyond, (1) exposes a parity doubling in the nucleon structure, (2) triggers drastic change in the nuclear tensor force and (3) stiffens the nuclear symmetry energy as density exceeds $n_{1/2}$. It results from an intricate interplay between the two hidden symmetries that the $\rho$ meson moves toward the vector manifestation (VM) fixed point where $m_\rho\rightarrow 0$ and the velocity of sound $v_s$ in the dense matter approaches the conformal symmetry value $v_s/c=\sqrt{1/3}$, indicating a presence of an infrared fixed point at which the dilaton mass vanishes.