The collapse of massive stars is believed to be the cause of
a number of the most energetic explosions in the universe
from supernovae to gamma-ray bursts. Stellar collapse forms
nearly all the neutron stars and stellar-massed black holes
in the universe and are the dominant contributors to the
heavy element abundances in galaxies. They produce
gravitational wave and neutrino signals that are detectable
for explosions in or near the Milky Way. The last few years
has seen considerable progress in our understanding of these
events. I will review these different fates, focusing on the
progress in recent years.
[D5.002] How fast, realistically: ab initio calculations of low-energy astrophysical reaction rates
Kenneth Nollett (Physics Division, Argonne National Laboratory)
Understanding the production of nuclei and nuclear energy in
astrophysical environments requires as input quantities the
rates of many nuclear reactions, but only a small fraction
of the cross sections required for nuclear astrophysics will
ever be measured in the laboratory. Nuclear astrophysics
will therefore always depend on nuclear theory to supply
rates fundamentally inaccessible in the laboratory, to
extrapolate measured cross sections to different energies or
mass numbers relevant for astrophysics, and to resolve
discrepancies where there are conflicting laboratory data.
Recent years have seen the development of the ``realistic''
nucleon-nucleon interactions that provide excellent
descriptions of nucleon-nucleon scattering up to the pion
production threshold. Computing wave functions and matrix
elements based on these interactions is
computation-intensive, even for the nuclei of atomic weight
twelve or less for which calculations are feasible with
present computers. Consequently, development of the
interactions and currents has gone hand-in-hand with
development of the computational methods to compute nuclear
wave functions and interaction matrix elements based on
them, particularly the quantum Monte Carlo and correlated
hyperspherical harmonic methods. These developments provide
an excellent opportunity for nuclear astrophysics, and they
have been applied fruitfully to several reactions of
astrophysical interest. I will review these advances in the
descriptions of light nuclei and their reactions, as well as
their application to specific reactions of interest for the
astrophysical problems of solar neutrino production and of
the synthesis of light nuclei in the early universe.
[D5.003] Ab initio calculations for light nuclei using realistic two- and three-body interactions
Petr Navratil (Lawrence Livermore National Laboratory)
Construction of accurate nucleon-nucleon potentials and
increases in computing power have led in recent years to the
development of new methods capable of solving the nuclear
structure problem for systems of more than four nucleons. In
this talk, I will describe one of these methods, the ab
initio no-core shell model. The principal foundation of this
approach is the use of effective interactions appropriate
for the large but finite basis spaces employed in the
calculations. These effective interactions are derived from
the underlying realistic inter-nucleon potentials by a
unitary transformation in a way that guarantees convergence
to the exact solution as the basis size increases. I will
discuss nuclear structure results for light nuclei up to
A=13 obtained by using several modern nucleon-nucleon
potentials, including those derived from the effective field
theory. The importance of the much-less-explored
three-nucleon forces for not only the binding energy but
also for the excitation spectra and some observables will be
highlighted.
[D5.004] Neutron matter calculations with quantum Monte Carlo
Kevin Schmidt (Arizona State University)
This abstract not available.
[D5.005] Lattice Studies of Hadronic Physics
David Richards (Jefferson Laboratory)
Lattice gauge calculations enable an ab initio exploration of QCD. In this talk, I review recent lattice results in hadronic physics, focusing on the computations of the moments of nucleon structure functions and generalized parton distributions (GPD's), and on the spectrum of excited resonances. I begin with an introduction to lattice QCD, outlining some of the theoretical and computational issues in lattice gauge calculations. I then proceed to describe some of the recent advances enabling computations to be performed at realistic values of the quark masses.
Structure functions and GPD's provide insight into the longitudinal and transverse structure of the nucleon, and their measurement is a crucial part of the hadronic physics experimental program. I describe how their moments are accessible to lattice calculation, and present the latest lattice results, studying in particular their dependence on the quark mass. Further insight into the dynamics of QCD is provided by a study of the spectrum. I review recent lattice results for the excited nucleon spectrum, and in particular for the Roper resonance and for the pentaquark, and describe how they might discriminate between different pictures of the nucleon. I conclude with prospects for future calculations.