A field theoretical model for quarkyonic matter

Abstract

The possibility that nuclear matter at a density relevant to the interior of massive neutron stars may be a quarkynoic matter has attracted considerable recent interest. In this work, we construct a phenomenological model to describe the quarkyonic matter, that would allow quantitative calculations of its various properties within a well-defined field theoretical framework. This is implemented by synthesizing the Walecka model together with the quark-meson model, where both quark and nucleon degrees of freedom are present based on the quarkyonic scenario. With this model we compute at mean-field level the thermodynamic properties of the symmetric nuclear matter and calibrate model parameters through well-known nuclear physics measurements. We find this model gives a very good description of the symmetric nuclear matter from moderate to high baryon density and demonstrates a continuous transition from nucleon-dominance to quark-dominance for the system.

The quarkyonic matter state of neutron stars

“…Previously, we constructed a field theoretical model for the isospin symmetric quark-baryonic (or quarkyonic) matter (QBM) [13] by combining the quark-meson model [16] with the well-known Walecka model [17]. By definition, quarkyonic matter belongs to the canonical ensemble where total densities are fixed but total energy could fluctuate [18].…”

“…Here, µ ′ p/n reflects the blocking effect from quarks and thus should depend on µ u/d [13]. Then, the total baryon density and minimization of F are enough to fix all the chemical potentials.…”

“…by following our previous scheme [13]. One should note here that we choose to work in the grand canonical en-semble for two reasons: it is more convenient to depict the blocking effect of quarks to nucleons and it better follows the philosophy of chiral symmetry breaking and restoration.…”

“…Second, the advanced detector NICER, installed aboard the International Space Station in 2017, could help to precisely measure the radii of neutron stars [6][7][8] and accordingly further constrain the hardness of the EOS. Finally, besides the color superconductivity phase inside the inner cores of neutron stars [9], the possibility of quarkyonic matter state has inspired new interests in an even wider community [10][11][12][13] .…”

“…Quarkyonic matter is a state where baryons coexist with deconfined quarks at high baryon density [14]: low-momentum quarks are free or quasi-free but highmomentum ones are mainly confined inside baryons. In our previous work [13], we tried to develop a complete field model for quarkyonic matter by considering baryons, quarks, and mesons in the same level and consistently taking chiral symmetry breaking and restoration into account. For the isospin symmetric case, we fixed free parameters by fitting to the saturation properties of stable nuclei and thus obtained pressure-density relation is consistent with the experimental constraints [15].…”