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We present numerical simulations of stellar core collapse with spherically symmetric, general relativistic hydrodynamics up to black hole formation. Using the COCONUT code, with a newly developed grey leakage scheme for the neutrino treatment, we investigate the effects of including pions and A hyperons into the equation of state at high densities and temperatures on the black hole formation process. Results show non-negligible differences between the models with reference equation of state without any additional particles and models with the extended ones. For the latter, the maximum masses supported by the proto-neutron star are smaller and the collapse to a black hole occurs earlier. A phase transition to hyperonic matter is observed when the progenitor allows for a high enough accretion rate onto the proto-neutron star. Rough estimates of neutrino luminosity from these collapses are given, too. [ABSTRACT FROM AUTHOR]

Some time ago a dispersive representation of the scalar Kπ form factor has been proposed. It does not only allow to limit the number of free parameters in the analysis of the experimental decay data on physically motivated ground, but the main interest is that it allows via the Callan-Treiman low-energy theorem to test the standard model precisely. This asks for a detailed study of the uncertainties of the dispersive representation which will be presented here. In addition, a dispesive representation of the vector form factor together with its uncertainties will be discussed. [Copyright &y& Elsevier]

Different scenarios of new physics beyond the standard model give rise to a direct coupling of right-handed quarks to W bosons. We will discuss how the prediction of the Callan-Treiman low energy theorem for the scalar form factor in combination with recent data on decays can serve as a stringent test of the standard model (SM) and possible extensions, in particular right-handed charged quark currents (RHCs). In addition, we will comment on the impact of hadronic tau decay data on RHCs. [Copyright &y& Elsevier]

With the recent dawn of the multimessenger 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 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. We find that they strongly impact the quark matter EoS. [ABSTRACT FROM AUTHOR]

We study the possible occurrence of the hadron-quark phase transition (PT) during the merging of neutron star binaries by hydrodynamical simulations employing a set of temperature-dependent hybrid equations of state (EOSs). Following previous work, we describe an unambiguous and measurable signature of deconfined quark matter in the gravitational-wave (GW) signal of neutron star binary mergers including equal-mass and unequal-mass systems of different total binary mass. The softening of the EOS by the PT at higher densities, i.e., after merging, leads to a characteristic increase of the dominant postmerger GW frequency f peak relative to the tidal deformability Λ inferred during the premerger inspiral phase. Hence, measuring such an increase of the postmerger frequency provides evidence for the presence of a strong PT. If the postmerger frequency and the tidal deformability are compatible with results from purely baryonic EOS models yielding very tight relations between f peak and Λ, a strong PT can be excluded up to a certain density. We find tight correlations of f peak and Λ with the maximum density during the early postmerger remnant evolution. These GW observables thus inform about the density regime which is probed by the remnant and its GW emission. Exploiting such relations, we devise a directly applicable, concrete procedure to constrain the onset density of the QCD PT from future GW measurements. We point out two interesting scenarios: if no indications for a PT are inferred from a GW detection, our procedure yields a lower limit on the onset density of the hadron-quark PT. On the contrary, if a merger event reveals evidence for the occurrence of deconfined quark matter, the inferred GW parameters set an upper limit on the PT onset density. Both scenarios would thus have strong implications for high-density matter physics, e.g., determining the range of validity of nuclear physics and constraining the properties for quark deconfinement. These prospects demonstrate the importance of simultaneously measuring pre- and postmerger GW signals to exploit the complementarity of the information encoded in both phases. Hence, our work stresses the value added by dedicated high-frequency GW instruments. [ABSTRACT FROM AUTHOR]