Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session R16: Nuclear Theory I |
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Sponsoring Units: DNP Chair: Anatolijs Afanasjevs, Mississippi State University Room: Hyatt Regency Jacksonville Riverfront City Terrace 12 |
Monday, April 16, 2007 10:45AM - 10:57AM |
R16.00001: Ergodicity of the $\Delta_3(L)$ statistic, in a RMT analysis of neutron resonance data Declan Mulhall, Zachary Huard, Vladimir Zelevinsky It is demonstrated that the $\Delta_3(L)$ of Random Matrix Theory (RMT) is not ergodic, in the sense that for a given GOE spectrum, $\Delta_3(L)$ can vary significantly from the predicted value. This leads to a natural spread that needs to be included when comparing the $\Delta_3(L)$ statistic of experimental data with the RMT result. However, this spread is smaller than the ensemble value usually quoted, and the possibility of extracting information about the mixing in spectra with superimposed sequences of levels is examined. An empirical expression for the appropriate ``error bars'' is given, and an analysis of neutron resonance data is performed. [Preview Abstract] |
Monday, April 16, 2007 10:57AM - 11:09AM |
R16.00002: Thermalization and Entropy in Nuclear Pairing Phase Transition Tony Sumaryada, Alexander Volya We present a study of pairing phase transitions in the mesoscopic nuclear systems. Our investigation includes analysis of different thermodynamic ensembles, study of discontinuities in associated thermodynamic variables, and examination of zeros of the partition functions in the complex plane. Apart from the traditional methods of thermodynamics we use an Invariant Correlational Entropy (ICE) as a new powerful tool to address the onset of nuclear superconductivity in individual quantum states. The ICE in an invariant and basis independent way characterizes the system in a given noise where pairing strength, a parameter of the Hamiltonian, is treated as a part of the statistical ensemble. Although, ICE is fundamentally different from the thermodynamic entropy we find the manifestations of the parameter driven noise to be very similar to that of the thermal ensemble. Thermalization of mesoscopic paired systems and related questions are also to be discussed. [Preview Abstract] |
Monday, April 16, 2007 11:09AM - 11:21AM |
R16.00003: The role of internal degrees of freedom in reactions with composite systems Naureen Ahsan, Alexander Volya The effects of the intrinsic structure of composite objects in quantum-mechanical processes, such as tunneling or scattering, are important components of nuclear fusion, fission, particle emission, and reaction physics in general. These processes are governed by non-perturbative physics with exponential sensitivity to various conditions. While a number of approximate methods to treat these problems are available, these techniques have their limitations and include approximations which, given the exponential sensitivity and non-perturbative nature of underlying physics, may lead to significant deviations from the exact results; furthermore, these deviations are often unexpected and counterintuitive. In this presentation we discuss the scattering and tunneling processes for a two-body system coupled by the harmonic oscillator or the infinite square well potentials. Assuming a deuteron-like behavior where only one of the particles interacts with the scattering potential (Coulomb force) we find the exact solution to this problem. This study reveals that while the problem is well defined, the mathematics and physics behind the solution are complicated. The virtual excitations into closed channels grow exponentially in the interaction region; even in the low-energy limit, the behavior of the solution shows strong sensitivity to the mass ratio of bound constituents and exhibits a resonant behavior. [Preview Abstract] |
Monday, April 16, 2007 11:21AM - 11:33AM |
R16.00004: The equation of state for spin-polarized cold nuclear matter Francesca Sammarruca, Plamen Krastev We proceed with our broad study of strongly asymmetric states of dense matter, where ``asymmetric'' may refer to spin and/or isospin asymmetries. In this paper we show and discuss recent results for the equation of state of spin-polarized {\it nuclear } matter. Comparison with the corresponding calculations we have recently performed for polarized {\it neutron} matter can give useful insight on how the presence of protons impacts the magnetic susceptibility or the closely related Landau parameter and, in turn, their potential instability with respect to spin oscillations. At this time, conclusions regarding the presence of such instability are very model dependent. For instance, characteristic differences are seen between the predictions of relativistic and non-relativistic calculations. Our approach being microscopic, we can perform an in-depth analysis of the physical origin of such differences and understand them in terms of specific features of the nuclear force in the medium. [Preview Abstract] |
Monday, April 16, 2007 11:33AM - 11:45AM |
R16.00005: Small-$x$ Nuclear shadowing from Diffractive Scattering Trang Nguyen, Adeola Adeluyi We calculate nuclear shadowing ratio at small Bjorken-$x$ for a wide range of nuclei in the framework of the Gribov theory. The diffractive dissociation cross sections, which are inputs, are taken from the FNAL and HERA experiments. We investigate the effects of the inclusion of subleading reggeons on shadowing. We compare our result with experimental data from the NMC and E665 experiments. [Preview Abstract] |
Monday, April 16, 2007 11:45AM - 11:57AM |
R16.00006: Is the Loop Expansion in Quantum Hadrodynamics Perturbative? Jeff McIntire, Brian Serot, Ying Hu Although one-loop calculations provide a realistic description of bulk and single-particle nuclear properties, it is necessary to examine loop corrections to develop a systematic finite-density power-counting scheme for the nuclear many-body problem when loops are included. Moreover, it is still imperative to study exchange and correlation corrections systematically, in order to make reliable predictions for other nuclear observables. One must also verify that the natural sizes of the one-loop parameters are not destroyed by explicit inclusion of many-body corrections. The loop expansion is applied to our chiral QHD lagrangian; with the techniques of Infrared Regularization, we found that it is possible to separate out the short-range contributions and to write them as products of fields that are already present in our lagrangian. (The appropriate field variables must be re-defined at each order in loops.) The corresponding parameters implicitly include short-range effects to all orders in the interaction, so these effects need not be calculated explicitly. The remaining (long-range) contributions that must be calculated resemble those in conventional nuclear-structure calculations (e.g. ladders, rings, etc.). As the interactions in QHD are relatively soft, one expects that the expansion will converge. While some of the terms are individually large, strong cancellation occurs. A calculation of the two and three-loop levels is conducted. [Preview Abstract] |
Monday, April 16, 2007 11:57AM - 12:09PM |
R16.00007: ABSTRACT HAS BEEN MOVED TO X16.00007 |
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