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Nuclear Theory·nucl-th

Wednesday·October 10, 2018

12 papers—5 primary·7 cross-listed

All12Primary5Cross-lists7
  1. 01

    Magnetic Vortex Lattices in Finite Isospin Chiral Perturbation Theory

    Prabal Adhikari🇺🇸

    We study finite isospin chiral perturbation theory (PT) in a uniform external magnetic field and find the condensation energy of magnetic vortex lattices using the method of successive approximations (originally used by Abrikosov) near the upper critical point beyond which the system is in the normal vacuum phase. The difference between standard Ginzburg-Landau (GL) theory (or equivalently the Abelian Higgs model) and PT arises due to the presence of additional momentum-dependent (derivative) interactions in PT and the presence of electromagnetically neutral pions that interact with the charged pions via strong interactions but do not couple directly to the external magnetic field. We find that while the vortex lattice structure is hexagonal similar to vortices in GL theory, the condensation energy (relative to the normal vacuum state in a uniform, external magnetic field) is smaller (larger in magnitude) due to the presence of derivative interactions. Furthermore, we establish that neutral pions do not condense in the vortex lattice near the upper critical field.

    nucl-thhep-phPLB(2019)·26 citations
  2. 02

    Deep learning: Extrapolation tool for ab initio nuclear theory

    Gianina Alina Negoita · James P. Vary · Glenn R. Luecke · Pieter Maris · Andrey M. Shirokov · Ik Jae Shin · Youngman Kim · Esmond G. Ng · Chao Yang · Matthew Lockner · Gurpur M. Prabhu

    Ab initio approaches in nuclear theory, such as the no-core shell model (NCSM), have been developed for approximately solving finite nuclei with realistic strong interactions. The NCSM and other approaches require an extrapolation of the results obtained in a finite basis space to the infinite basis space limit and assessment of the uncertainty of those extrapolations. Each observable requires a separate extrapolation and most observables have no proven extrapolation method. We propose a feed-forward artificial neural network (ANN) method as an extrapolation tool to obtain the ground state energy and the ground state point-proton root-mean-square (rms) radius along with their extrapolation uncertainties. The designed ANNs are sufficient to produce results for these two very different observables in Li from the ab initio NCSM results in small basis spaces that satisfy the following theoretical physics condition: independence of basis space parameters in the limit of extremely large matrices. Comparisons of the ANN results with other extrapolation methods are also provided.

    nucl-thcs.LGPRC(2019)·66 citations
  3. 03

    Real time description of fission

    I. Stetcu🇺🇸 · A. Bulgac🇺🇸 · S. Jin🇺🇸 · K. J. Roche🇺🇸 · N. Schunck🇺🇸

    Using the time-dependent superfluid local density approximation, the dynamics of fission is investigated in real time from just beyond the saddle to fully separated fragments. Simulations produced in this fully microscopic framework can help to assess the validity of the current approaches to fission, and to obtain estimate of fission observables. In this contribution, we concentrate on general aspects of fission dynamics.

    nucl-thCERN Proc.(2019)·3 citations
  4. 04

    Analysis of multinucleon transfer reactions involving spherical and statically deformed nuclei using a Langevin-type approach

    Vyacheslav Saiko · Alexander Karpov

    An increasing interest in multinucleon transfer processes in low-energy deep inelastic (damped) collisions of heavy ions appeared in recent years is due, in part, to by the possibility of using them as a method of production of heavy neutron-enriched nuclei. Possible promising projectile-target combinations include nuclei deformed in the ground state (e.g., actinides). Mutual orientations of such the nuclei in the entrance channel of the reaction may significantly influence the reaction dynamics. Available experimental data on multinucleon transfer reactions with statically deformed as well as spherical heavy nuclei 144Sm + 144Sm, 154Sm + 154Sm, 160Gd + 186W, and 208Pb + 208Pb/238U have been analyzed within the developed model. A good agreement of the calculated quantities with the corresponding experimental data is reached. Special attention in the paper is paid to analysis of production possibility of the neutron-enriched isotopes of heavy and superheavy elements in multinucleon transfer processes in the 238U + 238U/248Cm/254Es collisions.

    nucl-thPRC(2019)·85 citations
  5. 05

    Low-Energy Lepton-Proton Bremsstrahlung via Effective Field Theory

    Pulak Talukdar🇮🇳 · Fred Myhrer🇺🇸 · Ghanashyam Meher🇮🇳 · Udit Raha🇮🇳

    We present a systematic calculation of the cross section for the lepton-proton bremsstrahlung process l + p --> l' + p + gamma in chiral perturbation theory at next-to-leading order. This process corresponds to an undetected background signal for the proposed MUSE experiment at PSI. MUSE is designed to measure elastic scattering of low-energy electrons and muons off a proton target in order to extract a precise value of the proton's r.m.s. radius. We show that the commonly used peaking approximation, which is used to evaluate the radiative tail for the elastic cross section, is not applicable for muon-proton scattering at the low-energy MUSE kinematics. Furthermore, we point out a certain pathology with the standard chiral power counting scheme associated with electron scattering, whereby the next-to-next-to-leading order contribution from the pion loop diagrams is kinematically enhanced and numerically of the same magnitude as the next-to-leading order corrections. We correct a misprint in a commonly cited review article.

    nucl-thhep-phEPJA(2018)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE