Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session J4: Nuclear Theory |
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Sponsoring Units: DNP GFB Chair: Wayne Polyzou, University of Iowa Room: Garden 4 |
Sunday, May 1, 2011 1:30PM - 1:42PM |
J4.00001: Momentum-space Argonne V18 potential Saravanan Veerasamy, Wayne Polyzou We give two representations of the Argonne V18 potential in momentum space. The momentum-space potential is expressed as a linear combination of 24 spin-isospin operators with scalar coefficient functions of the momentum transfer. The coefficient functions are given by linear combinations of elementary functions or linear combinations of Chebyshev polynomials on a finite interval of momentum. Both provide practical and efficient representations for computing the momentum-space Argonne V18 potential that do not require integration or interpolation. Programs based on both expansions are publicly available. [Preview Abstract] |
Sunday, May 1, 2011 1:42PM - 1:54PM |
J4.00002: Finite-cutoff renormalization of the chiral NN potential Ruprecht Machleidt, Ehab Marji, Christopher Zeoli Naively, the ``best'' method of renormalization is the one where the momentum cutoff is taken to infinity while maintaining stable results. However, it has been shown for the chiral NN potential that this type of renormalization leads to a rather erratic scheme of power counting and does not allow for a systematic order-by-order improvement of the predictions. This should not come as a surprise, since the chiral effective field theory these potentials are based upon is designed for momenta below the chiral-symmetry breaking scale of about 1 GeV. Therefore, in the spirit of an investigation which Lepage conducted in 1997 for a toy model, we have examined the cutoff dependence of the predictions by the chiral NN potential at next-to-leading order (NLO) for phase shifts and NN observables using cutoffs below the hard scale with the goal to identify areas of cutoff independence (``plateaus''). The latest status of our results will be reported at the meeting. [Preview Abstract] |
Sunday, May 1, 2011 1:54PM - 2:06PM |
J4.00003: Integral relations in three-nucleon scattering Alejandro Kievsky I will discuss the description of scattering states using the Kohn Variational Principle (KVP). Recently, two integral relations have been derived from the KVP in order to obtain the scattering matrix. The integral relations depend on the wave function in the interaction region and, therefore, it is possible to determine the scattering matrix even if the asymptotic part of the wave function is not explicitely known. Some examples of the applicability of the integral relations will be shown. [Preview Abstract] |
Sunday, May 1, 2011 2:06PM - 2:18PM |
J4.00004: Isobar configurations in $^3$He ground state Rakhsha Nasseripour Studying the short-distance structure, the probabilities of short-range correlations (SRC) and meson-exchange currents in nuclei are important subjects in experimental nuclear physics that still have not been resolved. These processes, together with final-state interactions, contribute to the measured observables that are mostly being interpreted within strongly model-dependent pictures. The study of virtual nucleon excitations, specifically isobar configurations in the nuclear ground state, is an important part of this effort. Since the SRC are local high-density regions, it is likely that the quark distributions of nucleons would make a transition to non-nucleonic configurations. A number of theoretical calculations predict the probability of finding one or more nucleons in an excited state. In some studies, isobar excitations have been explicitly included in the few-body problem. Recent experiments at JLab provide an extensive data set of photon-induced reactions from nuclear targets. In this work we study various photoproduction channels that contain one or more $\Delta$-isobar configurations using an incident photon-beam energy of 0.5-1.5 GeV on a $^3$He target, for example, the $\gamma$$^3$He $\rightarrow \Delta^{++}nn$ or $\gamma$$^3$He $\rightarrow \Delta^{++} \Delta^0 n$ reactions. Preliminary results from these analyses and future plans will be discussed. [Preview Abstract] |
Sunday, May 1, 2011 2:18PM - 2:30PM |
J4.00005: Geometric phases in classical three-body dynamics Florence J. Lin In the classical dynamics of the $N$-body problem, a geometric phase is meaningful both physically and differential geometrically. Physically, a geometric phase corresponds to a net rotation due to nonzero internal angular momentum (with respect to a moving frame) contributing to the total angular momentum of a system. Differential geometrically, a geometric phase corresponds to a net rotation described by the holonomy of a connection. This result is demonstrated for the dynamics of a moving frame for three-body systems in terms of various coordinates, such as polar Jacobi coordinates, Guichardet coordinates, and the mutual distances between the bodies. In classical molecular dynamics,\footnote{F. J. Lin, {\it Discrete and Continuous Dynamical Systems Supplement} {\bf 2007}, 655 - 666 (2007).} geometric phases have been physically observed both experimentally and computationally. For example, a geometric phase has been observed experimentally in the rotation of the recoil angle of a departing atom in a dissociating triatomic molecule (a three-body system) due to rotation of the remaining diatomic fragment, and a geometric phase has been observed computationally in the overall rotation of a flexible protein molecule (an $N$-body system) due to its internal motions. [Preview Abstract] |
Sunday, May 1, 2011 2:30PM - 2:42PM |
J4.00006: Decoupling of Spurious Deep Bound States with the Similarity Renormalization Group K.A. Wendt, R.J. Furnstahl, R.J. Perry The Similarity Renormalization Group (SRG) is a continuous series of unitary transformations that can be implemented as a flow equation. When the relative kinetic energy ($T_{rel}$) is used in the SRG generator, nuclear structure calculations have shown greatly improved convergence with basis size because of the decoupling of high-energy and low-energy physics. However this generator can sometimes be problematic. A test case is provided by a study of initial interactions from chiral effective field theories with large cutoffs, which can lead to spurious deep bound states. We would like the SRG to decouple these from the physical shallow bound states. However, with~$T_{rel}$ the high- and low-energy bound states are not decoupled in the usual sense. Replacing~$T_{rel}$ by the momentum-space diagonal of the Hamiltonian ($H_d$) in the SRG generator does produce decoupling, such that the shallow states are in the low-momentum region and the deep bound states are at higher momentum. The flow toward universal low-momentum interactions is also restored. [Preview Abstract] |
Sunday, May 1, 2011 2:42PM - 2:54PM |
J4.00007: A light-front coupled cluster method for quantum field theories John Hiller, Sophia Chabysheva We describe a new method for the nonperturbative solution of quantum field theories. The exponential-operator technique of the traditional, many-body coupled-cluster method is adapted to the Fock-space eigenvalue problem for the light-front Hamiltionian. This leads to an effective eigenvalue problem in the valence Fock sector and a set of nonlinear integral equations for the functions that define the exponential operator. The approach avoids at least some of the difficulties associated with the Fock-space truncation usually used. [Preview Abstract] |
Sunday, May 1, 2011 2:54PM - 3:06PM |
J4.00008: Application of a light-front coupled cluster method Sophia Chabysheva, John Hiller As a test of the new light-front coupled-cluster method in a gauge theory, we apply it to the nonperturbative construction of the dressed-electron state in QED, for an arbitrary covariant gauge, and compute the electron's anomalous magnetic moment. The construction illustrates the spectator and Fock-sector independence of vertex and self-energy contributions and indicates resolution of the difficulties with uncanceled divergences that plague methods based on Fock-space truncation. [Preview Abstract] |
Sunday, May 1, 2011 3:06PM - 3:18PM |
J4.00009: Shear Viscosity of the normal phase of Unitary Fermi Gas from the Epsilon Expansion Andrei Kryjevski An analytical technique similar to the Epsilon expansion in the theory of critical phenomena has been proposed for dilute Fermi gas with two body interaction characterized by infinite scattering length and zero effective range dubbed Unitary Fermi Gas (Nishida and Son, Phys.Rev.Lett.97:050403, 2006). I will present a leading order calculation of the normal phase shear viscosity. The ratio of viscosity to the entropy density is predicted to exceed the AdS/CFT conjectured bound by a factor of about 6. [Preview Abstract] |
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