Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session JH: Calculational Methods in Nuclear Theory |
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Chair: Joseph Ginocchio, Los Alamos National Laboratory Room: Lamy |
Friday, November 5, 2010 2:00PM - 2:12PM |
JH.00001: Calculation of Few-Body Observables with the SRG Flow Equations E.R. Anderson, R.J. Furnstahl, R.J. Perry, S.K. Bogner, E.D. Jurgenson The Similarity Renormalization Group (SRG) flow equations are a series of unitary transformations which can be used to achieve different patterns of decoupling in a Hamiltonian. An SRG transformation applied to internucleon interactions leads to greatly improved convergence of energies in few- and many-body calculations. Not only does it provide a way to consistently evolve many-body potentials, but also other operators. Here, a method is presented to evolve and extract few-body operators, as well as to correct for evolution in a relative coordinate basis. These operators can be used to evaluate both low and high momentum quantities (e.g., electroweak observables, momentum distributions, etc.) in few- and many-body systems. The corresponding \textit{ab-initio} calculations are performed using the realistic 3D\ NCSM and with a 1D model (to gain insight into issues encountered in the realistic basis). Properties of the evolved operators will also be explored, as well as methods to improve convergence of matrix elements in truncated model spaces. [Preview Abstract] |
Friday, November 5, 2010 2:12PM - 2:24PM |
JH.00002: Constraining in-medium nucleon-nucleon interactions via nucleus-nucleus reactions Francesca Sammarruca, Larz White The nuclear equation of state is a broadly useful tool. Besides being the main input of stellar structure calculations, it allows a direct connection to the physics of nuclei. For instance, an energy functional (such as a mass formula), together with the energy/particle in nuclear matter, can be used to predict nuclear energies and radii [1]. The single-particle properties are also a key point to link infinite nuclear matter and actual nuclei. The parameters of the single-particle potential, in particular the effective mass, enter the calculations of, for instance, in-medium effective cross sections. From the well-known Glauber reaction theory, the total nucleus-nucleus reaction cross section is expressed in terms of the nuclear transparency, which, in turn, depends on the overlap of the nuclear density distributions and the elementary nucleon-nucleon (NN) cross sections. We explore the sensitivity of the reaction calculation to medium modifications of the NN cross sections to estimate the likelihood of constraining the latter through nuclear reactions. Ultimately, we wish to incorporate isospin asymmetry in the reaction model, having in mind connections with rare isotopes. [1] F. Sammarruca, arXiv:1002.00146 [nucl-th]; International Journal of Modern Physics, in press. [Preview Abstract] |
Friday, November 5, 2010 2:24PM - 2:36PM |
JH.00003: Toward ab initio DFT: Pairing and Optimized Effective Potential Joaquin Drut The quest for a universal nuclear energy density functional has stimulated research in many different areas of quantum many-body physics. Advances in the last decade have enabled quantum chemists to explicitly construct energy density functionals for the Coulomb interaction from first principles. This task was accomplished by extending the notion of density-dependent functionals to include explicit dependence on the Kohn-Sham orbitals. The resulting approach is usually called the Optimized Effective Potential (OEP). Are these developments useful in the nuclear case? Can one extend the OEP to include pairing? In this contribution we present some first answers to these and other related questions. [Preview Abstract] |
Friday, November 5, 2010 2:36PM - 2:48PM |
JH.00004: Cold Neutrons Confined in External Fields Stefano Gandolfi, Joe Carlson, Steven C. Pieper Advances in computational techniques and facilities now allow us to calculate the properties of N=8 to 54 neutrons with realistic interactions confined in external fields. By examining the shell structure, spin orbit, and pairing properties of these systems we can provide input to constrain nuclear density functionals, particularly their properties in the extreme isospin limit where the density functionals are less constrained. These density functionals are used to study the properties of large neutron-rich nuclei, and often to try to predict the properties of the inner crust of neutron stars. We find that these systems are sensitive to the isovector gradient terms in the density functional, and also to the spin-orbit and pairing terms in the extreme isospin limit. We show results for the ground some excited state energies, rms radii, and mass distributions for these confined systems, and compare with some typical Skyrme parametrizations of the density functional. Modifications to the Skyrme parameters to better describe these pure neutron systems are also described. [Preview Abstract] |
Friday, November 5, 2010 2:48PM - 3:00PM |
JH.00005: No-core full configuration calculations for neutron droplets James Vary, Pieter Maris We present recent results from no-core full configuration calculations for neutron droplets in an external field. We use several different NN interactions (JISP16, chiral N3LO, and Minnesota) and discuss the similarities and differences in the obtained energies, rms radii, and density profiles. We get good numerical convergence for up to 20 neutrons, and our results are in agreement with other methods. These results form an excellent basis for validation and verification of new energy-density functionals for nuclear physics. [Preview Abstract] |
Friday, November 5, 2010 3:00PM - 3:12PM |
JH.00006: Spin Density Matrices for Nuclear Density Functionals with Parity Violation Bruce Barrett, Bertrand Giraud Within the context of the radial density functional [1], we apply the spin density matrix (SDM) used in atomic and molecular physics [2] to nuclear physics. The vector part of the SDM defines a ``hedgehog'' situation, which exists only if nuclear states contain some amount of parity violation. Thus, looking for the vector profile of the SDM could be used as a test for parity violation in nuclei. The difference between the scalar profile and the vector profile of the SDM will be illustrated by a toy model. \\[4pt] [1] B. G. Giraud, Phys. Rev. C 78, 014307 (2008).\\[0pt] [2] A. Goerling, Phys. Rev. A 47, 2783 (1993). [Preview Abstract] |
Friday, November 5, 2010 3:12PM - 3:24PM |
JH.00007: Application of Evolved Three-Body Forces to P-Shell Nuclei Eric Jurgenson, Petr Navratil, Richard Furnstahl In recent years, the Similarity Renormalization Group has provided a powerful and versatile means to soften interactions for ab initio nuclear calculations. The large contribution of three-body forces to the nuclear interaction has required the consistent evolution of free-space Hamiltonians in the three-particle space. We present the most recent progress on this work, extending the calculations to the p-shell nuclei, and showing that the hierarchy of induced many-body forces is consistent with previous estimates. Calculations for A=6 including fully evolved NN+3N interactions show minor contributions due to induced four-body forces and display the same considerable convergence properties as in lighter nuclei. Preliminary results for independent operator evolution are also discussed. [Preview Abstract] |
Friday, November 5, 2010 3:24PM - 3:36PM |
JH.00008: Isotope Shifts Larry Zamick A three parameter formula (3P) for isotope shifts r$^2$(n)= n C +n)n-1)/2A+[n/2]B is related to he staggering parameter G= 2 [r$^2$(n+1)-r$^2$(n)]/[r$^{(n+2)}$-r$^2$(n)] If A+B=0 then G=1 (no staggering). If A=0 there is no n dependence to the staggering.One can get G to almost be plus or minus infinity for certain n,but this does not necessarily mean that there are major changes in the nuclear structure. We consider Potassium and Argon isotopes. We also consider quadrupole and monopole core polarization with a delta interaction. We vary the oscillator length parameter of the valence particle but keep the core values fixed. We find for both modes the amount of core polarization decreases as we increase the radius of the valence particle relative to that of the core (for small deviations from the case where the core and valence length parameters are the same). [Preview Abstract] |
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