Bulk viscosity of strange quark matter in density dependent quark mass model

We have studied the bulk viscosity of strange quark matter in the density dependent quark mass model (DDQM) and compared results with calculations done earlier in the MIT bag model where u, d masses were neglected and first order interactions were taken into account. We find that at low temperatures and high relative perturbations, the bulk viscosity is higher by 2 to 3 orders of magnitude while at low perturbations the enhancement is by 1–2 order of magnitude as compared to earlier results. Also the damping time is 2–3 orders of magnitude lower implying that the star reaches stability much earlier than in MIT bag model calculations.     

Neutrino emissivity of quark matter at finite temperatures

We evaluate the emissivity rates for d-decay and s-decay by exactly solving the angular integrals involved and without assuming the degeneracy of electrons. We have also studied the effects of QCD coupling constant as well as the s-quark mass on the emissivity rates. We find that these parameters are important in determining the threshold and extinction densities for d- and s-decays.     

Bulk viscosity of strange quark matter

We rederive the bulk viscosity of strange quark matter from the dominant reactionu + s ?d + u by taking the effect of temperature and quark-gluon coupling perturbatively to first order in the chemical composition of the quark matter. We also calculate the contribution from the β-decay processes s(d) →u + e + ¯v andu + e → s(d)+ v and show that this contribution has different temperature dependence and can even be larger than the contribution from the former reaction at temperatures of the order of the electron Fermi energy.     

Strange quark matter with dynamically generated quark masses

Bulk properties of strange quark matter (SQM) are investigated within the SU(3) Nambu–Jona-Lasinio model. In the chiral limit the model behaves very similarly to the MIT bag model which is often used to describe SQM. However, when we introduce realistic current quark masses, the strange quark becomes strongly disfavored, because of its large dynamical mass. We conclude that SQM is not absolutely stable.     

Neutrino emissivities in 2SC color-superconducting quark matter

The phase structure and equation of state for two-flavor quark matter under compact star constraints is studied within a nonlocal chiral quark model. Chiral symmetry breaking leads to rather large, density dependent quark masses at the phase transition to quark matter. The influence of diquark pairing gaps and quark masses on density dependent emissivities for the direct URCA is discussed. Since m _u > m _d , the direct URCA process due to quark masses cannot occur. We present cooling curves for model quark stars and discuss their relation to observational data. The text was submitted by the author in English.     

Dark matter, neutron stars, and strange quark matter

We show that self-annihilating weakly interacting massive particle (WIMP) dark matter accreted onto neutron stars may provide a mechanism to seed compact objects with long-lived lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV. This effect may trigger a conversion of most of the star into a strange star. We use an energy estimate for the long-lived strangelet based on the Fermi-gas model combined with the MIT bag model to set a new limit on the possible values of the WIMP mass that can be especially relevant for subdominant species of massive neutralinos.     

Properties of color-flavor locked strange quark matter and strange stars in a new quark mass scaling

Considering the effect of one-gluon-exchange interaction between quarks,the color-flavor locked strange quark matter and strange stars are investigated in a new quark mass density-dependent model.It is found that the color-flavor locked strange quark matter can be more stable if the one-gluon-exchange effect is included.The lower density behavior of the sound velocity in this model is different from the previous results.Moreover,the new equation of state leads to a heavier acceptable maximum mass,supporting the recent observation of a compact star mass as large as about 2 times the solar mass.     

Magnetized strange quark matter in a mass-density-dependent model

We investigate the properties of strange quark matter (SQM) in a strong magnetic field with quark confinement by the density dependence of quark masses considering the total baryon number conservation, charge neutrality and chemical equilibrium. It is found that an additional term should appear in the pressure expression to maintain thermodynamic consistency. At fixed density, the energy density of magnetized SQM varies with the magnetic field strength. By increasing the field strength an energy minimum exists located at about 6×10¹⁹ Gauss when the density is fixed at two times the normal nuclear saturation density.     

Emission of droplets of strange quark matter in RHIC

We demonstrate that strangeness separates in the quark-hadron coexistence (even atT=0) and prompt kaon emission results in a strong enhancement of thes-quark abundance in the quark phase during the phase transition to hadron matter. Condensation into stabilized droplets of strange quark matter (“strangelets”) does occur during the phase transition. The so formed cool, compact, long-lived clusters could be experimentally observed by their smallZ/A-ratio. If the late quark matter phase is unstable, it should be observable by the delayed, correlated emission of several hyperons.     

Review of experimental searches for strange quark matter states

In this proceedings, we review the current status of experimental searches for novel forms of nuclear matter, namely strange quark matter states. A detailed summary of H-dibaryon results is given and implications on the stability of such a state is reviewed. Final results from the BNL-AGS and CERN-SPS strangelet searches are presented and put in the context of coalescence and plasma production models.     

Astrophysical bounds on the properties of strange quark matter

Constraints on the size of the Coulomb barrier and the universal abundance of stable strange quark matter are calculated assuming that the evolution of stars and the nucleosynthesis at stellar sites are not dominated by strange quark matter. The results are applied to find the minimum required beam energy and sensitivity in a heavy ion activation search for strange quark matter in laboratory samples.