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Register a new userSurface tension of quark droplets in compact stars and in the early universe
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We review the role of the surface tension of quark matter droplets in astrophysical conditions, focusing specifically on the thermodynamic conditions prevailing in cold neutron stars (NSs), in hot lepton rich proto NSs, and in early universe conditions. We analyze quark matter in chemical equilibrium under weak interactions, which is relevant for understanding the internal composition of hybrid stars, as well as just deconfined quark matter out of chemical equilibrium, which is the relevant thermodynamic state for describing the nucleation process of quark matter in NSs. We explore the role of temperature, density, trapped neutrinos, droplet size and magnetic fields within the multiple reflection expansion formalism (MRE). Quark matter is described within the frame of different effective models: the MIT bag model and the $SU(3)_f$ Nambu-Jona-Lasinio model (NJL), including color superconductivity, neutrino trapping and magnetic fields. We also analyze the deconfinement transition at vanishing chemical potential and finite temperature including the Polyakov loop. We explore some astrophysical consequences of our results.
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In spite of its key role in compact star physics, the surface tension of quark matter is not well comprehended yet. In this work we analyze the behavior of the surface tension of three-flavor quark matter in the outer and inner core of cold deleptonized magnetars, proto magnetars born in core collapse supernovae, and hot magnetars produced in binary neutron stars mergers. We explore the role of temperature, baryon number density, trapped neutrinos, droplet size, and magnetic fields within the multiple reflection expansion formalism. Quark matter is described within the MIT bag model and is assumed to be in chemical equilibrium under weak interactions. We discuss some astrophysical consequences of our results.
Compactness is introduced as a new method to search for the onset of the quark matter transition in relativistic heavy ion collisions. That transition supposedly leads to stronger compression and higher compactness of the source in coordinate space. That effect could be observed via pion interferometry. We propose to measure the compactness of the source in the appropriate principal axis frame of the compactness tensor in coordinate space.
We study the multiplicity and rapidity dependence of thermal and prompt photon production in p+Pb collisions at 5.02 TeV, using a (3+1)D viscous hydrodynamic framework. Direct photon anisotropic flow coefficients $v^gamma_{2,3}$ and nuclear modification factor $R^gamma_mathrm{pPb}(p_T)$ are presented in both the p-going (backward) and the Pb-going (forward) directions. The interplay between initial state cold nuclear effect and final state thermal enhancement at different rapidity regions is discussed. The proposed rapidity dependent thermal photon enhancement and direct photon anisotropic flow observables can elucidate non-trivial longitudinal dynamics of hot quark-gluon plasma droplets created in small collision systems.
Recent indications for high neutron star masses (M sim 2 M_sun) and large radii (R > 12 km) could rule out soft equations of state and have provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. We show that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. For these objects color superconductivity turns out to be an essential ingredient for a successful description of the cooling phenomenology in accordance with recently developed tests. We discuss the energy release in the neutrino untrapping transition as a new aspect of the problem that hybrid stars masquerade themselves as neutron stars. Quark matter searches in future generations of low-temperature/high-density nucleus-nucleus collision experiments such as low-energy RHIC and CBM @ FAIR might face the same problem of an almost crossover behavior of the deconfinement transition. Therefore, diagnostic tools shall be derived from effects of color superconductivity.
Based on an equivparticle model, we investigate the in-medium quark condensate in neutron stars. Carrying out a Taylor expansion of the nuclear binding energy to the order of $rho^3$, we obtain a series of EOSs for neutron star matter, which are confronted with the latest nuclear and astrophysical constraints. The in-medium quark condensate is then extracted from the constrained properties of neutron star matter, which decreases non-linearly with density. However, the chiral symmetry is only partially restored with non-vanishing quark condensates, which may vanish at a density that is out of reach for neutron stars.
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