Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session C11: Nuclear Theory I |
Hide Abstracts |
Sponsoring Units: DNP Chair: Lucas Platter, University of Tennessee Room: A220-221 |
Saturday, April 14, 2018 1:30PM - 1:42PM |
C11.00001: Decoupling of bound states with the Magnus expansion and the in-medium similarity renormalization group. Anthony Tropiano, Scott Bogner, Richard Furnstahl, Nathan Parzuchowski The coupling of high- and low-momentum modes in nuclear Hamiltonians complicates ab initio nuclear structure calculations. The in-medium similarity renormalization group (IM-SRG) softens nucleon-nucleon interactions by applying a continuous unitary transformation to the Hamiltonian to decouple low- and high-momentum scales. Here we study differences between evolving nuclear Hamiltonians with the typical IM-SRG approach and with the implementation of the Magnus expansion by applying these approaches to a leading-order nucleon-nucleon potential in momentum space that features a spurious, deep bound state at higher chiral effective field theory cutoffs. We consider both the Wegner and Wilson SRG generators. We find that the Magnus implementation converges to the typical SRG approach. With the Wegner SRG generator, the Magnus expansion can be used to soften nuclear potentials without shifting deeply bound states in the low-energy scale, and the SRG flow equations can be solved with a crude ODE solver without loss of accuracy in the eigenvalues of the evolved operator. [Preview Abstract] |
Saturday, April 14, 2018 1:42PM - 1:54PM |
C11.00002: Bayesian error analysis for phenomenological nuclear interactions Rodrigo Navarro Perez Phenomenological interactions have played a central role in nuclear physics since the early studies of the nucleus more than six decades ago. While microscopically derived interactions have recently shown major improvements in terms of description of experimental data and a wider range of applicability, phenomenological interactions remain the most commonly used type of interactions both for structure and reaction calculations. Although a great deal of effort is usually dedicated to determining an optimal set of parameters that best describe a large body of experimental data, the problem of quantifying uncertainties is left untouched in most cases. The reason for this lack of quantified uncertainties in phenomenological interactions is sometimes related to the already large computational cost of minimizing a $\chi^2$ type of merit figure with respect to the interaction parameters. In this work we discuss early developments in applying Bayesian analysis and Markov Chain Monte Carlo methods to identify the posterior distribution of an already optimized set of parameters. In particular we look at an updated version of the popular AV18 potential. Further possible applications into systematic uncertainties of chiral potential as well as optical potentials are also discussed. [Preview Abstract] |
Saturday, April 14, 2018 1:54PM - 2:06PM |
C11.00003: Medium effects in infinite neutron matter using in-medium similarity renormalizaton group (IM-SRG) technique Sarath Srinivas Saravanan, Sunethra Ramanan Neutron matter at high density is extensively studied in the context of neutron star core. Due to high densities in the inner layers of the crust and outer layers of the core, the nucleon-nucleon interaction could be significantly altered by the medium. Such medium corrections to the interaction are an important ingredient in many body calculations such as the equation of state, pairing, etc. In this talk, we employ IM-SRG to construct a medium corrected interaction in infinite matter for a given free space interaction. IM-SRG is a continuous unitary transformation of the Hamiltonian which is normal ordered with respect to the filled Fermi level. It has the advantage of incorporating few body interactions consistently. We derive the IM-SRG flow equations by incorporating momentum conservation for a spin polarised fermion gas as a preliminary step. The solution of the flow equation at the leading order is similar to the vertex corrections encountered in many body perturbation theory (MBPT). Further, the flow equation contains terms similar to that of BCS as well as the ZS and ZS' terms from the Fermi liquid theory. We outline the set-up of the flow equations and discuss its numerical solution for infinite matter without recourse to discrete basis states. [Preview Abstract] |
Saturday, April 14, 2018 2:06PM - 2:18PM |
C11.00004: Brueckner-Hartree-Fock calculations in the Density Matrix Expansion approach Yinu Zhang, Scott Bogner, Richard Furnstahl Recently, a microscopically based nuclear energy density functional was derived by applying the Density Matrix Expansion to the Hartree-Fock energy obtained from long-range chiral effective field theory two- and three-nucleon interactions. The Hartree-Fock approach cannot contain the full many-body correlations. Brueckner-Hartree-Fock theory gives an improved definition of the one-body potential U by replacing the interaction by a reaction matrix G. The central result of modern renormalization theory is that a general RG decoupling generates an infinite series of counterterms consistent with the input interaction. Then we can apply the DME at Hartree-Fock level with long-range $\chi$EFT interactions and zero-range contact interactions to model BHF correlations. [Preview Abstract] |
Saturday, April 14, 2018 2:18PM - 2:30PM |
C11.00005: Reduced Density Matrix Mechanics with Neutron Drops Alexander Dyhdalo, Richard Furnstahl Despite impressive strides made in the last few decades, solving the quantum many-body problem for nuclear systems remains a challenge. We propose adopting a novel many-body method developed in quantum chemistry over the past few decades and applying it to nuclear systems. This method, termed reduced density matrix mechanics, utilizes properties of the one- and two-body density matrices and semidefinite programming to solve the many-body system. Here, we apply this method to a system of neutron drops interacting via the semi-realistic Minnesota potential. [Preview Abstract] |
Saturday, April 14, 2018 2:30PM - 2:42PM |
C11.00006: Scale dependence of short-range correlations with the in-medium similarity renormalization group Nathan Parzuchowski, Richard Furnstahl, Scott Bogner In recent years, the nuclear physics community has made a considerable effort to understand the nature of the short-range correlation (SRC) scaling factor $a_2$. Even though SRCs are a property of the nuclear wave function and are thus non-observable, recent theoretical work suggests that the ratio of SRCs between two nuclei is both scale and scheme independent. This ratio, denoted by $a_2$, has been obtained experimentally for nuclei ranging from the deuteron to $^{197}$Au, but has only been computed for very light nuclei thus far. In this work, we have employed the in-medium similarity renormalization group (IMSRG) as a means to compute $a_2$ for intermediate mass nuclei, allowing us to test the supposed observable nature of $a_2$ for a wide range of systems. In order to obtain accurate descriptions, we explore infrared extrapolations in quantities relevant to $a_2$. These explorations can help shed light on the convergence features of many nuclear physics quantities computable with modern many-body methods. [Preview Abstract] |
Saturday, April 14, 2018 2:42PM - 2:54PM |
C11.00007: Fission dynamics within time-dependent density functional theory Shi Jin, Aurel Bulgac, Kenneth Roche, Nicolas Schunck, Ionel Stetcu We present results for the low energy induced fission of 240Pu within the time-dependent density functional theory (TDDFT) extended to superfluid phenomena, using two nuclear energy density functionals, SeaLL1 and SkM*. We conclude the pairing correlation play a crucial role and during the saddle-to-scission the dynamics is strongly overdamped, due to the one-body dissipation mechanism. Scission is organically incorporated into the formalism and the properties of the emerging fission fragments are controlled by shell effects and pairing correlations. The heavy fragment emerges close to spherical and cooler than the light fragment, which is highly deformed and reaches eventually a higher temperature. We extract the average mass and charge values, the kinetic and the excitation energies of the fission fragments, and the properties of the emitted neutrons during scission and during the initial acceleration of the fission fragments. All evaluated properties are in good agreement with observations. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700