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Nuclear Theory·nucl-th

Friday·June 13, 2025

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 01

    Gapless superfluidity in neutron stars: Normal-fluid fraction

    Valentin Allard · Nicolas Chamel

    Our previous investigation within the time-dependent nuclear energy-density functional theory showed that the nuclear superfluids contained inside cold neutron stars could become gapless under certain circumstances. The absence of a gap in the energy spectrum of quasiparticle excitations leads to a specific heat that is comparable to that in the normal phase in sharp contrast with the exponential suppression in the BCS phase of type pairing. Here, we further study gapless superfluidity within the same microscopic framework focusing on hydrodynamic properties. In particular, we calculate the mass fraction transported by the normal fluid of quasiparticle excitations, and we find that it can be finite even at zero temperature. We derive an approximate analytical formula for arbitrary neutron-proton superfluid mixtures. We also present numerical results for neutron stars. Our study suggests that the dynamics of neutron stars may be much more complicated than previously thought. The realization of gapless superfluidity in neutron stars and its implications are discussed.

    nucl-thastro-ph.HEPRC(2023)·9 citations
  2. 02

    Geometry of Configuration Mixing in Bose-Fermi Systems

    A. Leviatan · N. Gavrielov

    A geometric interpretation for an algebraic interacting boson-fermion model with configuration mixing is presented. The formalism is based on an extended Bose-Fermi matrix coherent states and is applied to gain insight on intertwined quantum shape-phase transitions and shape coexistence in odd-mass Nb nuclei.

    nucl-thquant-phPLB(2025)·5 citations
  3. 03

    HFB3: an axial HFB solver with Gogny forces using a 2-center HO basis (C++/Python)

    N. Dubray🇫🇷 · J. P. Ebran🇫🇷 · P. Carpentier🇫🇷 · M. Frosini🇫🇷 · A. Zdeb🇫🇷 · N. Pillet🇫🇷 · J. Newsome🇫🇷 · M. Verrière🇫🇷 · G. Accorto🇫🇷 · D. Regnier🇫🇷

    The HFB3 program solves the axial nuclear Hartree-Fock-Bogoliubov (HFB) equations using bases formed by either one or two sets of deformed Harmonic Oscillator (HO) solutions with D1-type and D2-type Gogny effective nucleon-nucleon interactions. Using two sets of HO solutions shifted along the z-axis (2-center basis) allows to accurately describe highly elongated nuclear systems while keeping a moderate basis size, making this type of basis very convenient for the description of the nuclear fission process. For the description of odd-even and odd-odd systems, the equal-filling-approximation is used. Several observables can be calculated by the program, including the mean values of the multipole moments, nuclear radii, inertia tensors following Adiabatic Time-Dependent Hartree-Fock-Bogoliubov (ATDHFB) or Generator Coordinate Method (GCM) prescriptions, local and non-local one-body densities, local and non-local pairing densities, some fission fragment properties, etc. The program can ensure that the mean values associated with some specific operators take pre-defined values (constraints). Such constraints can be set on the usual multipole moments (for protons, neutrons or total mass). This program can be used as a monoprocess and monothreaded CLI executable, or through full-featured Python bindings (available through the Python Package Index PyPI).

    nucl-thEPJA(2025)·3 citations
  4. 04

    Microscopic theory of angular momentum distributions across the full range of fission fragments

    Petar Marević🇭🇷 · Nicolas Schunck🇺🇸 · Marc Verriere🇺🇸

    Modern nuclear theory provides qualitative insights into the fundamental mechanisms of nuclear fission and is increasingly capable of making reliable quantitative predictions. Most quantities of interest pertain to the primary fission fragments, whose subsequent decay is typically modeled using statistical reaction models. Consequently, a key objective of fission theory is to inform these models by predicting the initial conditions of the primary fragments. In this work, we employ a framework that combines joint angular momentum and particle number projection with time-dependent configuration mixing to calculate the angular momentum distributions of primary fragments. Focusing on the benchmark cases of neutron-induced fission of U and Pu, we predict - for the first time - microscopic angular momentum distributions for all fragments observed in experiments. Our results reveal a pronounced sawtooth pattern in the average angular momentum as a function of fragment mass, consistent with recent measurements. Additionally, we observe substantial variations in angular momentum distributions along isobaric chains, indicating that commonly used empirical formulas lack sufficient accuracy. We also quantify a strong correlation between the angular momentum and the deformation of the fragments at scission, and a weak correlation in the magnitude of the angular momentum between fragment partners. The generated data will enable estimation of the impact of microscopic distributions on fission spectra, paving the way toward fission modeling based on microscopic inputs.

    nucl-thPRC(2026)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE