Abstract
With the recent dawn of the multi-messenger astronomy era a new window has opened to explore the constituents of matter and their interactions under extreme conditions. One of the pending challenges of modern physics is to probe the microscopic equation of state (EoS) of cold and dense matter via macroscopic neutron star observations such as their masses and radii. Still unanswered issues concern the detailed composition of matter in the core of neutron stars at high pressure and the possible presence of e.g. hyperons or quarks. By means of a non-perturbative functional renormalization group approach the influence of quantum and density fluctuations on the quark matter EoS in $\beta$-equilibrium is investigated within two- and three-flavor quark-meson model truncations and compared to results obtained with common mean-field approximations where important fluctuations are usually ignored. We find that they strongly impact the quark matter EoS.
Highlights
The recent clean mass determinations for two pulsars, PSR J1614 − 2230 and PSR J0348 þ 0432 [1], confirm the existence of neutron stars (NS) with a mass of about—and possibly even beyond, see [2]—two solar masses
One of the pending challenges of modern physics is to probe the microscopic equation of state (EoS) of cold and dense matter via macroscopic neutron star observations such as their masses and radii
By means of a nonperturbative functional renormalization group approach the influence of quantum and density fluctuations on the quark matter EoS in β-equilibrium is investigated within two- and three-flavor quark-meson model truncations and compared to results obtained with common mean-field approximations where important fluctuations are usually ignored
Summary
The recent clean mass determinations for two pulsars, PSR J1614 − 2230 and PSR J0348 þ 0432 [1], confirm the existence of neutron stars (NS) with a mass of about—and possibly even beyond, see [2]—two solar masses. The parameters are adjusted to existing constraints from nuclear experiments, observations and/or theoretical calculations, including attempts to extract the density dependence of the EoS directly from NS mass and radius data. The considered quantum and density fluctuations are of particular importance in the vicinity of phase transitions and are usually ignored in mean-field approximations These might be some reasons for the recent growing interest in the application of the FRG method to neutron star matter [29,30]. The paper is organized as follows: after a brief setup of the used effective quark-meson model for quark matter, in Sec. II, three different approximations of the grand potential are presented which incorporate various contributions of certain quantum, thermal and density fluctuations. Parameter choices and numerical details can be found in the Appendixes A and B
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