Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session GH: Astrophysics: Modelling |
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Chair: Lee Bernstein, Lawrence Livermore National Laboratory Room: Jewett Ballroom F |
Saturday, October 25, 2008 10:30AM - 10:42AM |
GH.00001: Molecular dynamics simulations of the crust of accreting neutron stars Charles Horowitz We model the crust of accreting neutron stars with molecular dynamics simulations involving complex compositions with many different impurities as predicted by rapid proton capture nucleosynthesis and electron capture calculations. We present results for the phase structure [1], thermal conductivity, and screening factors for nuclear reactions [2]. We find a lattice structure with a high thermal conductivity, instead of an amorphous solid, and we discuss the distribution of impurities. These thermal conductivity results agree with X-Ray observations of crust cooling for neutron stars after extended outbursts. We find that screening factors for the enhancement of thermonuclear reactions may be insensitive to the large scale distribution of impurities in the solid. Fusion of neutron rich oxygen isotopes such as $^{24}$O + $^{24}$O may be an important heat source at densities near ten to the eleventh g/cm$^{3}$. Indeed these and similar fusion reactions may be important to heat the crust to carbon ignition temperatures in superbursts. [1] C. J. Horowitz, D. K. Berry, and E. F. Brown, PRE75 (2007) 066101. [2] C. J. Horowitz, H. Dussan, and D. K. Berry, arXiv:0710.5714. [Preview Abstract] |
Saturday, October 25, 2008 10:42AM - 10:54AM |
GH.00002: ABSTRACT WITHDRAWN |
Saturday, October 25, 2008 10:54AM - 11:06AM |
GH.00003: Viscosity and r-mode damping in stars with quark matter Gautam Rupak, Prashanth Jaikumar, Andrew W. Steiner The effect of shear and bulk viscosity on $r$-mode oscillations in compact stars with quark matter is presented. We consider both the ungapped and gapped color-flavor-locked (CFL) phase of quark matter. In ungapped quark phase $r$-mode is damped for temperatures $10^8$ K $-5\times 10^9$ K even for rapid rotations whereas in CFL phase $r$-mode is not damped in the temperature range $10^{10}$ K $-10^{11}$ K. We find viscous damping of $r$-mode in quark matter leads to larger critical frequencies and smaller spin-periods compared to rotating neutron stars. [Preview Abstract] |
Saturday, October 25, 2008 11:06AM - 11:18AM |
GH.00004: Non-inertial effects in reactions of astrophysical interest Junting Huang, Carlos Bertulani, Plamen Krastev We report on novel effects due to non-inertial motion in reactions occurring in stars, and elsewhere. Applying Einstein's equivalence principle, we explore the corrections induced by strong gravitational fields on nuclear reactions in massive and/or compact stars. We find that non-inertial effects will appreciably modify the excitation processes in nuclear and atomic collisions. [Preview Abstract] |
Saturday, October 25, 2008 11:18AM - 11:30AM |
GH.00005: Detection of supernovae neutrinos with neutrino-iron scattering Arturo Samana, Carlos Bertulani The $\nu_e-^{56}$Fe cross section is evaluated in the projected quasiparticle random phase approximation (PQRPA). This model solves the puzzle observed in RPA for nuclei with mass around $^{12}$C, because it is the only RPA model that treats the Pauli principle correctly. The cross sections as a function of the incident neutrino energy are compared with recent theoretical calculations of similar models. The average cross section weighted with the flux spectrum yields a good agreement with the experimental data. The expected number of events in the detection of supernova neutrinos is calculated for the LVD detector leading to an upper limit for the electron neutrino energy of particular importance in this experiment. [Preview Abstract] |
Saturday, October 25, 2008 11:30AM - 11:42AM |
GH.00006: Transport properties of nucleons Sergey Postnikov, Madappa Prakash Results for the coefficients of diffusion, thermal conductivity, bulk and shear viscosities of a homogeneous system of nucleons will be presented. In the nondegenerate regime, the Chapman-Enskog theory provides an approximate solution to the Boltzmann equation and casts the transport properties in terms of appropriate transport integrals. In this case, the necessary differential cross sections are calculated using phase shifts extracted from scattering experiments. In the degenerate regime, many-body methods developed in the context of liquid helium-3 are employed. Techniques to cover the partially degenerate regime are also explored. The extent to which these transport coefficients are relevant in the dynamical evolutions of supernovae and neutron stars will be examined. [Preview Abstract] |
Saturday, October 25, 2008 11:42AM - 11:54AM |
GH.00007: Nuclear constraints on properties of rotating neutron stars Plamen Krastev, Aaron Worley, Bao-An Li Nuclear reactions with radioactive beams provide unique means to constrain the equation of state (EOS) of neutron-rich matter, in particular its density dependence through the nuclear symmetry energy. The EOS is important for our understanding of numerous phenomena in both nuclear physics and astrophysics. In this talk we will present our most recent results on the properties of rotating neutron stars with a particular emphasis on rapid rotations. [Preview Abstract] |
Saturday, October 25, 2008 11:54AM - 12:06PM |
GH.00008: Determining Entropy Generation in the Early Universe / Links to CMBR Spectra {\&} neutrino and relic graviton production issues Andrew Beckwith We analyze how entropy is generated via a semiclassical argument as well as by multiple brane- anti brane combinations leading to an initial soliton-instanton formation. The supposition is that the two different types of methods give similar initial conditions for entropy and information/ computational bits of information in the initial universe. We close then with observations we think are pertinent to entropy increase and also the variation of statistical noise about the CMBR spectra. This ties in with possible new species of detectable `neutrinos' which lead to an extension of the standard model, since the derived `axion' is coupled to photons to the tune of $f_a =\vartheta (10^{15}GeV)$ which is too large for Earthbound experiments (but which is in the range of space based experiments/ data collection of astro physical phenomena, which could be detected by analysis of the CMBR spectra). This if there is a tie in with relic gravitons and the new neutrino candidate, indicates new detection schemes for both, which could be detected by both the new Li-Baker gravity wave detector, as well as Ice Cube. [Preview Abstract] |
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