Neutron star matter equation of state including d^*-hexaquark degrees of freedom

Abstract

We present an extension of a previous work where, assuming a simple free bosonic gas supplemented with a relativistic meand field model to describe the pure nucleonic part of the EoS, we studied the consequences that the first non-trivial hexaquark d * (2380) could have on the properties of neutron stars. Compared to that exploratory work we employ a standard non-linear Walecka model including additional terms that describe the interaction of the d * (2380) di-baryon with the other particles of the system through the exchange of σand ω-meson fields. Our results have show that the presence of the d * (2380) leads to maximum masses compatible with the recent observations of ∼ 2M ⊙ millisecond pulsars if the interaction of the d * (2380) is slightly repulsive or the d * (2380) does not interacts at all. An attractive interaction makes the equation of state too soft to be able to support a 2M ⊙ neutron star whereas an extremely repulsive one induces the collapse of the neutron star into a black hole as soon as the d * (2380) appears.

Dibaryons: Molecular versus compact hexaquarks *

“…Because appears to exist in nuclear matter, it can influence the nuclear equation of state, especially in compact stellar objects such as neutron stars. A study finds that appears at densities three times the saturation density and constitutes approximately 20% of the matter in the center of neutron stars [161], depending on the assumed interaction of with its surroundings [162]. Moreover, because dibaryons are bosons, one may consider a Bose-Einstein condensate formed by hexaquarks.…”

Systematic analysis of inner crust composition using the extended Thomas-Fermi approximation with pairing correlations

“…Due to a strong pressure gradient, the matter within a Neutron Star (NS) organises itself into different layers [1]. Near the surface of the star lies the crust, where neutrons and protons are arranged in nuclear clusters in a crystalline structure, that transitions gradually into a liquid phase [2] approaching the core of the star [3].…”

Dibaryons: Molecular versus Compact Hexaquarks

“…Since d * (2380) appears to exist in nuclear matter, it can influence the nuclear equation of state, especially in compact stellar objects like neutron stars. A study finds d * (2380) to appear at densities three times the saturation density and to constitute around 20% of the matter in the center of neutron stars [135] depending on the assumed interaction of d * (2380) with its surroundings [136].…”