Simulations of Core Collapse Supernovae In One and Two Dimemsions Using Multigroup Neutrino Transport

In one dimension, we present results from comparisons of stationary state multigroup flux-limited diffusion and Boltzmann neutrino transport, focusing on quantities central to the postbounce shock reheating. In two dimensions, we present results from simulations that couple one-dimensional multigroup flux-limited diffusion to two-dimensional PPM hydrodynamics.Comment: Latex, using sprocl.sty, 3 pages, To appear in the proceedings of the 18th Texas Symposium on Relativistic Astrophysic

A Better Pipeline to the Principalship

Describes the design and outcomes of Atlanta's Superintendent's Academy for Building Leaders in Education, a Wallace-funded program that encourages reflection, collaboration, problem-solving, and communication to improve teaching and student achievement

Technique for Evaluating Multiple Probability Occurrences /TEMPO/

Technique is described for adjustment of engineering response information by broadening the application of statistical subjective stimuli theory. The study is specifically concerned with a mathematical evaluation of the expected probability of relative occurrence which can be identified by comparison rating techniques

Conservative formulations of general relativistic kinetic theory

Experience with core-collapse supernova simulations shows that accurate accounting of total particle number and 4-momentum can be a challenge for computational radiative transfer. This accurate accounting would be facilitated by the use of particle number and 4-momentum transport equations that allow transparent conversion between volume and surface integrals in both configuration and momentum space. Such conservative formulations of general relativistic kinetic theory in multiple spatial dimensions are presented in this paper, and their relevance to core-collapse supernova simulations is described.Comment: 48 page

Supernova neutrino challenges

A principal `supernova neutrino challenge' is the computational difficulty of six-dimensional neutrino radiation hydrodynamics. The variety of resulting approximations has provoked a long history of uncertainty in the core-collapse supernova explosion mechanism, but recent work highlighting low-mode convection and a newly-recognized instability in spherical accretion shocks may signal (yet another) resolution. As part of its goal of elucidating the explosion mechanism, the Terascale Supernova Initiative is committed to meeting the full complexity of the computational challenge. The understanding of supernova neutrino emission gained in detailed simulations provides a potential basis for learning about two major remaining unknowns in neutrino flavor mixing: the value of the mixing angle $\theta_{13}$, and distinguishing between ``normal'' and ``inverted'' mass hierarchies.Comment: 6 pages. Contribution to the proceedings of NOW2004, Conca Specchiulla (Otranto, Italy), September 11-17, 2004, to be published by Nucl. Phys. B (Proc. Suppl.), ed. P. Bernardini, G.L. Fogli, and E. Lis

Dark matter sterile neutrinos in stellar collapse: alteration of energy/lepton number transport and a mechanism for supernova explosion enhancement

We investigate matter-enhanced Mikheyev-Smirnov-Wolfenstein (MSW) active-sterile neutrino conversion in the $\nu_e \rightleftharpoons \nu_s$ channel in the collapse of the iron core of a pre-supernova star. For values of sterile neutrino rest mass $m_s$ and vacuum mixing angle $\theta$ (specifically, $0.5 {\rm keV} 5\times{10}^{-12}$) which include those required for viable sterile neutrino dark matter, our one-zone in-fall phase collapse calculations show a significant reduction in core lepton fraction. This would result in a smaller homologous core and therefore a smaller initial shock energy, disfavoring successful shock re-heating and the prospects for an explosion. However, these calculations also suggest that the MSW resonance energy can exhibit a minimum located between the center and surface of the core. In turn, this suggests a post-core-bounce mechanism to enhance neutrino transport and neutrino luminosities at the core surface and thereby augment shock re-heating: (1) scattering-induced or coherent MSW $\nu_e\to\nu_s$ conversion occurs deep in the core, at the first MSW resonance, where $\nu_e$ energies are large ($\sim 150$ MeV); (2) the high energy $\nu_s$ stream outward at near light speed; (3) they deposit their energy when they encounter the second MSW resonance $\nu_s\to\nu_e$ just below the proto-neutron star surface.Comment: 13 pages, 9 figure

Simulation of Coherent Non-Linear Neutrino Flavor Transformation in the Supernova Environment I: Correlated Neutrino Trajectories

We present results of large-scale numerical simulations of the evolution of neutrino and antineutrino flavors in the region above the late-time post-supernova-explosion proto-neutron star. Our calculations are the first to allow explicit flavor evolution histories on different neutrino trajectories and to self-consistently couple flavor development on these trajectories through forward scattering-induced quantum entanglement. Employing the atmospheric-scale neutrino mass-squared difference and values of theta_13 allowed by current bounds, we find transformation of neutrino and antineutrino flavors over broad ranges of energy and luminosity in roughly the ``bi-polar'' collective mode. We find that this large-scale flavor conversion, largely driven by the flavor off-diagonal neutrino-neutrino forward scattering potential, sets in much closer to the proto-neutron star than simple estimates based on flavor-diagonal potentials and Mikeheyev-Smirnov-Wolfenstein evolution would indicate. In turn, this suggests that models of r-process nucleosynthesis sited in the neutrino-driven wind could be affected substantially by active-active neutrino flavor mixing, even with the small measured neutrino mass-squared differences.Comment: 23 pages, 12 figures, revtex4 format. Version accepted by PR

Sterile Neutrino-Enhanced Supernova Explosions

We investigate the enhancement of lepton number, energy, and entropy transport resulting from active-sterile neutrino conversion $\nu_e\to\nu_s$ deep in the post-bounce supernova core followed by re-conversion $\nu_s\to\nu_e$ further out, near the neutrino sphere. We explicitly take account of shock wave and neutrino heating modification of the active neutrino forward scattering potential which governs sterile neutrino production. We find that the $\nu_e$ luminosity at the neutrino sphere could be increased by between $\sim 10$ and $\sim 100$ during the crucial shock re-heating epoch if the sterile neutrino has a rest mass and vacuum mixing parameters in ranges which include those required for viable sterile neutrino dark matter. We also find sterile neutrino transport-enhanced entropy deposition ahead of the shock. This `` pre-heating\rq\rq can help melt heavy nuclei and thereby reduce the nuclear photo-dissociation burden on the shock. Both neutrino luminosity enhancement and pre-heating could increase the likelihood of a successful core collapse supernova explosion.Comment: 12 pages, 4 figure