Nuclear matter

About: Nuclear matter is a research topic. Over the lifetime, 10180 publications have been published within this topic receiving 248261 citations.

Bulk viscosity of hot-neutron-star matter from direct URCA processes

Abstract: Direct URCA processes, occurring in neutron-star matter with a proton fraction exceeding the critical value of (11-15)%, can strongly enhance the bulk viscosity of the matter.

Momentum-dependent nuclear mean fields and collective flow in heavy-ion collisions.

Abstract: We use the Boltzmann-Uehling-Uhlenbeck model to simulate the dynamical evolution of heavy-ion collisions and to ocmpare the effects of two parametrizations of the momentum-dependent nuclear mean field that have identical properties in cold nuclear matter. We compare with recent data on nuclear flow, as characterized by transverse momentum distributions and flow ([ital F]) variables for symmetric and asymmetric systems. We find that the precise functional dependence of the nuclear mean field on the particle momentum is important. With our approach, we also confirm that the difference between symmetric and asymmetric systems can be used to pin down the density and momentum dependence of the nuclear self-consistent one-body potential, independently. All the data can be reproduced very well with a momentum-dependent interaction with an equilibrium nuclear matter compressibility [ital K]=210 MeV.

Hot neutron matter from a Self-Consistent Green's Functions approach

Abstract: A systematic study of the microscopic and thermodynamical properties of pure neutron matter at finite temperature within the self-consistent Green's-function approach is performed. The model dependence of these results is analyzed by both comparing the results obtained with two different microscopic interactions, the CD Bonn and the Argonne V18 potentials, and by analyzing the results obtained with other approaches, such as the Brueckner-Hartree-Fock approximation, the variational approach, and the virial expansion.

Off-shell behavior of the in-medium nucleon-nucleon cross-section

Abstract: The properties of nucleon-nucleon scattering inside dense nuclear matter are investigated. We use the relativistic Brueckner-Hartree-Fock model to determine on-shell and half off-shell in-medium transition amplitudes and cross sections. At finite densities the on-shell cross sections are generally suppressed. This reduction is, however, less pronounced than found in previous works. In case the outgoing momenta are allowed to be off energy shell the amplitudes show a strong variation with momentum. This description allows one to determine in-medium cross sections beyond the quasiparticle approximation, accounting thereby for the finite width which nucleons acquire in the dense nuclear medium. For reasonable choices of the in-medium nuclear spectral width, i.e., $\ensuremath{\Gamma}l~40\mathrm{MeV},$ the resulting total cross sections are, however, reduced by not more than about 25% compared to the on-shell values. Off-shell effects are generally more pronounced at large nuclear matter densities.

Nucleon effective masses within the Brueckner-Hartree-Fock theory: Impact on stellar neutrino emission

Abstract: We calculate the effective masses of neutrons and protons in dense nuclear matter within the microscopic Brueckner-Hartree-Fock many-body theory and study the impact on the neutrino emissivity processes of neutron stars. We compare results based on different nucleon-nucleon potentials and nuclear three-body forces. Useful parametrizations of the numerical results are given. We find substantial in-medium suppression of the emissivities, strongly dependent on the interactions.