Superfluidity in neutron stars and cold atoms

We discuss superfluidity in neutron matter, with particular attention to induced interactions and to universal properties accessible with cold atoms.Comment: 3 pages, 2 figures, talk at Quark Confinement and the Hadron Spectrum VII, Ponta Delgada, September 2006, one reference correcte

Nuclear astrophysics and electron beams

Electron beams provide important probes and constraints for nuclear astrophysics. This is especially exciting at energies within the regime of chiral effective field theory (EFT), which provides a systematic expansion for nuclear forces and electroweak operators based on quantum chromodynamics. This talk discusses some recent highlights and future directions based on chiral EFT, including nuclear structure and reactions for astrophysics, the neutron skin and constraints for the properties of neutron-rich matter in neutron stars and core-collapse supernovae, and the dark matter response of nuclei.Comment: 8 pages, 7 figures, proceedings of plenary talk at MIT Workshop on Polarized Electron Beams, March 14-16, 201

Three-nucleon forces and nuclei at the extremes

Neutron-rich nuclei become increasingly sensitive to three-nucleon forces. These components of nuclear forces are at the forefront of theoretical developments based on effective field theories of quantum chromodynamics. We discuss our understanding of three-nucleon forces and their impact on exotic nuclei, and show how new measurements test and constrain them. Three-nucleon forces therefore provide an exciting link between theoretical and experimental nuclear physics frontiers.Comment: 6 pages, 7 figures, proceedings of the International Symposium on Exotic Nuclear Structure from Nucleons (ENSFN2012), Tokyo, October 10-12, 201

Neutrino Bremsstrahlung in Neutron Matter from Effective Nuclear Interactions

We revisit the emissivity from neutrino pair bremsstrahlung in neutron-neutron scattering, nn -> nn nu nubar, which was calculated from the one-pion exchange potential including correlation effects by Friman and Maxwell. Starting from the free-space low-momentum nucleon-nucleon interaction V_{low k}, we include tensor, spin-orbit and second-order medium-induced non-central contributions to the scattering amplitude in neutron matter. We find that the screening of the nucleon-nucleon interaction reduces the emissivity from neutrino bremsstrahlung for densities below nuclear matter density. We discuss the implications of medium modifications for the cooling of neutron stars via neutrino emission, taking into account recent results for the polarization effects on neutron superfluidity.Comment: 9 pages, 3 figures, minor revisions, to appear in Phys. Lett.

Three-body interactions in Fermi systems

We show that the contributions of three-quasiparticle interactions to normal Fermi systems at low energies and temperatures are suppressed by n_q/n compared to two-body interactions, where n_q is the density of excited or added quasiparticles and n is the ground-state density. For finite Fermi systems, three-quasiparticle contributions are suppressed by the corresponding ratio of particle numbers N_q/N. This is illustrated for polarons in strongly interacting spin-polarized Fermi gases and for valence neutrons in neutron-rich calcium isotopes.Comment: 16 pages, 1 figure; to appear in Festschrift on the occasion of Gerry Brown's 85th birthday, Ed. Sabine Lee (World Scientific