Cold quark matter

Abstract

We perform an Oð 2 s Þ perturbative calculation of the equation of state of cold but dense QCD matter with two massless and one massive quark flavor, finding that perturbation theory converges reasonably well for quark chemical potentials above 1 GeV. Using a running coupling constant and strange quark mass, and allowing for further nonperturbative effects, our results point to a narrow range where absolutely stable strange quark matter may exist. Absent stable strange quark matter, our findings suggest that quark matter in (slowly rotating) compact star cores becomes confined to hadrons only slightly above the density of atomic nuclei. Finally, we show that equations of state including quark matter lead to hybrid star masses up to M $ 2M , in agreement with current observations. For strange stars, we find maximal masses of M $ 2:75M and conclude that confirmed observations of compact stars with M > 2M would strongly favor the existence of stable strange quark matter.

Fast spinning strange stars: possible ways to constrain interacting quark matter parameters

“…In fact, the simple version of the MIT bag model EoS can be extended to include perturbative corrections due to quark interactions, up to the second order (O(α 2 s )) in the strong structure constant αs (Freedman & McLerran 1977, 1978Baluni 1978;Fraga et al 2001;Kurkela et al 2010) 1 . Within this modified bag model one can thus evaluate the non-ideal behaviour of the EoS of cold SQM at high density.…”

Rapid cooling of Cassiopeia A as a phase transition in dense QCD

“…Models that predict quark matter in such massive compact stars in color-superconducting states have been studied extensively (Alford et al 2005a;Klähn et al 2007;Ippolito et al 2008;Knippel & Sedrakian 2009;Kurkela et al 2010;Bonanno & Sedrakian 2012). Color superconductivity is important; otherwise, the unpaired quarks cool a star by neutrino emission rapidly to temperatures well below those observed in Cas A (Page et al 2000;Alford et al 2005b;Anglani et al 2006;Grigorian et al 2005;Hess & Sedrakian 2011).…”

Neutron Star Structure with Hyperons and Quarks

“…4 (black curves). The most striking effect of the inclusion of quark matter is the increase of the maximum mass relative to the hyperon star, now reaching about 1.5 M for the MIT models with a bag constant B = 100 MeV/fm −3 or with B(ρ), about 1.6 M for the more sophisticated color dielectric model (CDM) [17,22], and about 1.8 M in a recent O(α 2 s ) calculation [18].…”

“…This surprising result is due to the strong softening of the baryonic EOS when including hyperons as additional degrees of freedom, and one does not expect substantial changes when introducing refinements of the theoretical framework, such as hyperon-hyperon potentials, hyperonic TBF [14], relativistic corrections, etc.. The only remaining possibility to reach larger maximum masses appears the transition to another phase of dense (quark) matter inside the star [15][16][17][18].…”