Topology Change and Tensor Forces for the EoS of Dense Baryonic Matter

TL;DR

This paper investigates how topology change in dense baryonic matter, modeled via skyrmions, affects the equation of state and tensor forces, providing insights into neutron star properties and nuclear interactions.

Contribution

It introduces a novel approach linking topology change to modifications in the EoS and tensor forces, impacting neutron star modeling and nuclear physics.

Findings

Topology change leads to a transition from Fermi liquid to non-Fermi liquid.

Approximately 80% of nucleon mass remains invariant, indicating a non-chiral origin.

The modified tensor forces stiffen the EoS, supporting 2-solar-mass neutron stars.

Abstract

When skyrmions representing nucleons are put on crystal lattice and compressed to simulate high density, there is a transition above the normal nuclear matter density $n_0$ from a matter consisting of skyrmions with integer baryon charge to a state of half-skyrmions with half-integer baryon charge. We exploit this observation in an effective field theory formalism to access dense baryonic system. We find that the topology change involved implies a changeover from a Fermi liquid structure to a non-Fermi liquid with the chiral condensate in the nucleon "melted off." The $\sim 80%$ of the nucleon mass that remains, invariant under chiral transformation, points to the origin of the (bulk of) proton mass that is not encoded in the standard mechanism of spontaneously broken chiral symmetry. The topology change engenders a drastic modification of the nuclear tensor forces, thereby nontrivially affecting the EoS, in particular, the symmetry energy, for compact star matter. It brings in stiffening of the EoS needed to accommodate a neutron star of $\sim 2$ solar mass. The strong effect on the EoS in general and in the tensor force structure in particular will also have impact on processes that could be measured at RIB-type accelerators.