PaperPanorama
FAQ

Nuclear Theory·nucl-th

Monday·June 26, 2023

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    Maximally local two-nucleon interactions at NLO in -less chiral effective field theory

    Rahul Somasundaram · Joel E. Lynn · Lukas Huth · Achim Schwenk · Ingo Tews

    We present new maximally local two-nucleon interactions derived in -less chiral effective field theory up to next-to-next-to-next-to-leading order (NLO), which include all contact and pion-exchange contributions to the nuclear Hamiltonian up to this order. Our interactions are fit to nucleon-nucleon phase shifts using a Bayesian statistical approach, and explore a wide cutoff range from fm ( MeV). These interactions can be straightforwardly employed in quantum Monte Carlo methods, such as the auxiliary field diffusion Monte Carlo method. Together with local three-nucleon forces, calculations with these new interactions will provide improved benchmarks for the structure of atomic nuclei and serve as crucial input to analyses of astrophysical phenomena of neutron stars, such as binary neutron-star mergers.

    nucl-thPRC(2024)·30 citations
  2. 02

    Bulk viscosity from Urca processes: matter in the neutrino-transparent regime

    Mark Alford🇺🇸 · Arus Harutyunyan🇦🇲 · Armen Sedrakian🇩🇪

    We study the bulk viscosity of moderately hot and dense, neutrino-transparent relativistic matter arising from weak-interaction direct Urca processes. This work parallels our recent study of the bulk viscosity of matter with a trapped neutrino component. The nuclear matter is modeled in a relativistic density functional approach with two different parametrizations -- DDME2 (which does not allow for the low-temperature direct-Urca process at any density) and NL3 (which allows for low-temperature direct-Urca process above a low-density threshold). We compute the equilibration rates of Urca processes of neutron decay and lepton capture, as well as the rate of the muon decay, and find that the muon decay process is subdominant to the Urca processes at temperatures MeV in the case of DDME2 model and MeV in the case of NL3 model. Thus, the Urca-process-driven bulk viscosity is computed with the assumption that pure leptonic reactions are frozen. As a result the electronic and muonic Urca channels contribute to the bulk viscosity independently and at certain densities the bulk viscosity of matter shows instead of the standard one-peak (resonant) form a "flattened" shape. In the final step, we estimate the damping timescales of density oscillations by the bulk viscosity. We find that, e.g., at a typical oscillation frequency kHz, the damping of oscillations is most efficient at temperatures MeV and densities where they can affect the evolution of the post-merger object.

    nucl-thastro-ph.HEhep-phPRD(2023)·25 citations
  3. 03

    Converging Many-Body Perturbation Theory for Ab Initio Nuclear-Structure: I. Brillouin-Wigner Perturbation Series for Closed-Shell Nuclei

    Zhen Li🇫🇷 · Nadezda A. Smirnova🇫🇷

    Convergence aspects of nuclear many-body perturbation theory for ground states of closed-shell nuclei are explored using a Brillouin-Wigner formulation with a new vertex function enabling high-order calculations. A general formalism for Hamiltonian partitioning and a convergence criterion for the perturbation series are proposed. Analytical derivation shows that with optimal partitionings, the convergence criterion for ground states can always be satisfied. This feature attributes to the variational principle and does not depend on the choice of an internucleon interaction or a many-body basis. Numerical calculations of the ground state energies of 4He and 16O with Daejeon16 and a bare N3LO potential in both harmonic-oscillator and Hartree-Fock bases confirm this finding.

    nucl-thPLB(2024)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE