Frankfurt Institute for Advanced Studies

About: Frankfurt Institute for Advanced Studies is a facility organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Baryon & Quark–gluon plasma. The organization has 798 authors who have published 2733 publications receiving 82799 citations. The organization is also known as: FIAS.

Neutrino-pair emission from nuclear de-excitation in core-collapse supernova simulations

Abstract: We study the impact of neutrino-pair production from the de-excitation of highly excited heavy nuclei on core-collapse supernova simulations, following the evolution up to several 100 ms after core bounce. Our study is based on the agile-boltztransupernova code, which features general relativistic radiation hydrodynamics and accurate three-flavor Boltzmann neutrino transport in spherical symmetry. In our simulations the nuclear de-excitation process is described in two different ways. At first we follow the approach proposed by Fuller and Meyer [Astrophys. J. 376, 701 (1991)], which is based on strength functions derived in the framework of the nuclear Fermi-gas model of noninteracting nucleons. Second, we parametrize the allowed and forbidden strength distributions in accordance with measurements for selected nuclear ground states. We determine the de-excitation strength by applying the Brink hypothesis and detailed balance. For both approaches, we find that nuclear de-excitation has no effect on the supernova dynamics. However, we find that nuclear de-excitation is the leading source for the production of electron antineutrinos as well as heavy-lepton-flavor (anti)neutrinos during the collapse phase. At sufficiently high densities, the associated neutrino spectra are influenced by interactions with the surrounding matter, making proper simulations of neutrino transport important for the determination of the neutrino-energy loss rate. We find that, even including nuclear de-excitations, the energy loss during the collapse phase is overwhelmingly dominated by electron neutrinos produced by electron capture.

Photon emission from a momentum-anisotropic quark-gluon plasma

Abstract: We compute the photon emission rate from a quark-gluon plasma with an anisotropic particle momentum distribution induced by a nonvanishing local shear pressure tensor. Our calculation includes photon production through Compton scattering and quark-antiquark annihilation at leading order in ${\ensuremath{\alpha}}_{s}$, with all off-equilibrium corrections to leading order in the momentum anisotropy. For fermions we prove that the Kubo-Martin-Schwinger relation holds in the hard loop regime for any particle momentum distribution function that is reflection symmetric. This supports the equivalence, for 2-to-2 scattering processes, of the diagrammatic and kinetic approaches to calculating the photon emission rate. We compare the viscous rates from these two approaches at weak and realistic coupling strengths and provide parametrizations of the equilibrium and viscous photon emission rates for phenomenological studies in relativistic heavy-ion collisions.

New scenarios for hard-core interactions in a hadron resonance gas

Abstract: The equation of state of baryon-symmetric hadronic matter with hard-sphere interactions is studied It is assumed that mesons $M$ are pointlike, but baryons $B$ and antibaryons $\overline{B}$ have the same hard-core radius ${r}_{B}$ Three possibilities are considered: (1) the $BB$ and $B\overline{B}$ interactions are the same; (2) baryons do not interact with antibaryons; (3) the $B\overline{B}, MB$, and $M\overline{B}$ interactions are negligible By choosing the parameter ${r}_{B}=03--06$ fm, we calculate the nucleon to pion ratio as a function of temperature and perform the fit of hadron yields measured in central Pb+Pb collisions at $\sqrt{{s}_{NN}}=276\phantom{\rule{016em}{0ex}}\mathrm{TeV}$ New nontrivial effects in the interacting hadron resonance gas at temperatures $150--200$ MeV are found