### Session D2: Gravitation, Cosmology, High Energy and Nuclear Physics

Chair: David Weeks
Room: SC 106

 Saturday, April 9, 2005 8:00AM - 8:12AM D2.00001: Gravity and Atomic Tests of Lorentz Symmetry Jay D. Tasson , V. Alan Kostelecky Lorentz violation is a promising candidate signal for new physics arising from a fundamental theory at the Planck scale. Low-energy effects of these violations are described by the Standard-Model Extension (SME). An outline of the fermion sector of this theory in the presence of gravity is provided, along with a discussion of some associated phenomenology. Saturday, April 9, 2005 8:12AM - 8:24AM D2.00002: The Lorentz-Violating Post-Newtonian Expansion Quentin G. Bailey , V. Alan Kostelecky The possibility that Lorentz violation offers a signature of Planck-scale physics has motivated recent experimental searches. At accessible energy scales any effects must be described by the Standard-Model Extension (SME). In this talk, I focus on the gravitational sector of the SME. Dominant solar-system effects are discussed in the context of a post-Newtonian expansion. Saturday, April 9, 2005 8:24AM - 8:36AM D2.00003: Towards photon intensity interferometry in relativistic heavy-ion collisions Evan Frodermann Hanbury-Brown-Twiss (HBT) intensity interferometry is a powerful tool that probes the size of the fireball in a heavy ion collision. Pion interferometry accesses the final state of the fireball, and its information is focussed at the time of decoupling from strong interactions. Photon interferometry, however, can probe geometry and dynamics of the initial stages of the fireball and may lead to insights into the space-time evolution of a quark-gluon plasma. In this contribution the one particle photon emission rate from a (2+1)-dimensional hydrodynamic evolution of the fireball is investigated. This emission rate is the first step in calculating full HBT radii using thermal photons, including all relevant production processes. Saturday, April 9, 2005 8:36AM - 8:48AM D2.00004: Anisotropic flow and jet suppression in ultrarelativistic U+U collisions Anthony Kuhlman Full overlap collisions between large, deformed nuclei, such as U, provide an opportunity to examine a number of unresolved issues from RHIC. These collisions are capable of producing energy densities up to 50\% larger than those in central Au+Au collisions, yielding an outstanding laboratory to test the ideal hydrodynamic behavior of $v_2$. In addition, in edge-on-edge collisions, the 25\% deformation allows the path length dependence of parton energy loss to be tested to large transverse momenta. We illustrate the advantages to be gained from the implementation of a U+U program at RHIC with a number of quantitative calculations and provide a Monte Carlo simulation which demonstrates the results to be expected from such a program. This work is supported by the Department of Energy. Saturday, April 9, 2005 8:48AM - 9:00AM D2.00005: Quark-Hadron Duality Sabine Jeschonnek , J.W. Van Orden Quark-hadron duality is an interesting phenomenon that occurs in many different processes. It was first observed in inclusive electron scattering by Bloom and Gilman, and has been confirmed recently by high precision data from Jefferson Lab. The data show that the structure function in the resonance region averages to the scaling curve. One of the main practical uses of duality is the extraction of information on the deep inelastic region from the resonance data. I will discuss a model for the study of quark-hadron duality in inclusive electron scattering based on solving the Dirac equation numerically for a scalar confining linear potential and a vector color Coulomb potential. This model qualitatively reproduces the features of quark-hadron duality for all potentials considered. Saturday, April 9, 2005 9:00AM - 9:12AM D2.00006: Time Dependent Nuclear Scattering Calculations David Weeks , Brian Davis A new time dependent method for calculating scattering matrix elements of two and three body nuclear collisions below 50 Mev is being developed. The procedure closely follows the channel packet method (CPM) used to compute scattering matrix elements for non-adiabatic molecular reactions.\footnote{T.A.Niday and D.E.Weeks, Chem. Phys. Letters \textbf{308} (1999) 106} Currently, one degree of freedom calculations using a simple square well have been completed and a two body scattering calculation using the Yukawa potential is anticipated. To perform nuclear scattering calculations with the CPM that will incorporate the nucleon-nucleon tensor force, we plan to position initial reactant and product channel packets in the asymptotic limit on single coupled potential energy surfaces labeled by the spin, isospin, and total angular momentum of the reactant nucleons. The wave packets will propagated numerically using the split operator method augmented by a coordinate dependant unitary transformation used to diagonalize the potential. Scattering matrix elements will be determined by the Fourier transform of the correlation function between the evolving reactant and product wave packets. A brief outline of the Argonne v$_{18}$ nucleon-nucleon potential\footnote{R.B.Wiringa, V.G.J.Stoks, and R.Schiavilla, Physical Review C \textbf{51}(1995) 38} and the proposed wave packet calculations will be presented. Saturday, April 9, 2005 9:12AM - 9:24AM D2.00007: Gravitational N-body Simulation of Galactic Clusters Erica Blasdel , Stephen Alexander We have extended a gravitational N-body simulation code that has been used for solar system studies to the scale of stellar clusters. We have used this code to simulate the dynamics of open or galactic stellar clusters that are characterized by a few hundred newly formed stars embedded in the gas and dust cloud from which they formed. We report on the results of simulations that study the stability of the cluster as the remnant cloud is dispersed over the time-scale of a few million years. Saturday, April 9, 2005 9:24AM - 9:36AM D2.00008: Dark Matter and Energy as Antimatter Wayne Lundberg A new interpretation of dark matter observations via gravitational lensing through galaxy clusters is proposed. Gravitational lensing studies of SDSS J1004+4112 by Williams and Saha (astro-ph/0412445) indicate that any dark matter contribution to lensing is smoothly distributed in space. All particle theories (i.e WIMPs) which propose to explain dark matter inevitably yield gravitational clumping. Note that string theory requires that matter at radii, R, less than the Planck scale, $\surd \alpha$', is equivalent to matter at distance D=$\alpha$'/R. The proposed interpretation involves antimatter existing within anti-deSitter spaces to explain the unexpected smoothness. This proposal asserts that a (non-Hawking) black hole exists with an AdS space at its singularity. Antimatter interactions also explain Galactic Annihilation Fountain(s) and similar observed phenomena. Non-temporal matter is thereby defined as matter which exists in 4-space, either advanced or retarded wrt the present. A radical' form of cosmology is then developed in which the curvature tensor of Einstein's general relativity is treated as complex. FRW cosmology plus dark matter and energy results. Theories regarding the black hole `end state'' and~Seiberg's chronology protection lend support to this approach. Previous work (\href{http://www-astro-theory.fnal.gov/Conferences/cosmo02/poster/lundberg.pdf}{http://www-astro-theory.fnal.gov/Conferences/cosmo02/poster/lundberg.pdf}) to establish the architecture of a comprehensive theory is thus modified.