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

Low-momentum interactions for nuclei

We show how the renormalization group is used to construct a low-momentum nucleon-nucleon interaction V_{low k}, which unifies all potential models used in nuclear structure calculations. V_{low k} can be directly applied to the nuclear shell model or to nucleonic matter without a G matrix resummation. It is argued that V_{low k} parameterizes a high-order chiral effective field theory two-nucleon force. We use cutoff dependence as a tool to assess the error in the truncation of nuclear forces to two-nucleon interactions and introduce a low-momentum three-nucleon force, which regulates A=3,4 binding energies. The adjusted three-nucleon interaction is perturbative for small cutoffs. In contrast to other precision interactions, the error due to missing many-body forces can be estimated, when V_{low k} and the corresponding three-nucleon force are used in nuclear structure calculations and the cutoff is varied.Comment: 10 pages, 5 figures, talk at INT workshop on Nuclear Forces and the Quantum Many-Body Problem, Seattle, October 200

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

Symmetry energy, neutron skin, and neutron star radius from chiral effective field theory interactions

We discuss neutron matter calculations based on chiral effective field theory interactions and their predictions for the symmetry energy, the neutron skin of 208 Pb, and for the radius of neutron stars.Comment: 7 pages, 8 figures, short review article, to appear in EPJA special issue on symmetry energ