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Nuclear Theory·nucl-th

Monday·June 29, 2026

13 papers—6 primary·7 cross-listed

All13Primary6Cross-lists7
  1. 07

    [Submitted on 25 Jun 2026] (cross-list from astro-ph.HE)

    Impact of neutrino-electron scattering and an improved treatment of pair processes on binary neutron star mergers

    Francois Foucart🇺🇸 · Samantha Rath🇺🇸 · Rowan Davidson🇺🇸 · Patrick Chi-Kit Cheong🇺🇸 · Matthew D. Duez🇺🇸 · Lawrence Kidder🇺🇸 · Harald Pfeiffer🇩🇪 · Mark Scheel🇺🇸

    Multimessenger observations of neutron star mergers are unique opportunities to constrain the properties of dense matter and the production site of heavy nuclei. To leverage these observations, we require reliable models of the electromagnetic signals powered by mergers. An important limitation to our ability to develop such models is the use of approximate neutrino physics in simulations. Here, we present simulations using an improved version of our Monte Carlo transport algorithm specifically designed to allow for more advanced on-the-fly calculations of reaction rates that use the simulated energy distribution of neutrinos, including in blocking factors, while still relying on approximations for the angular distribution of neutrinos. We use these new methods to include in simulations inelastic scattering of neutrinos on electrons, and to improve our treatment of neutrino-antineutrino pair annihilation. We find that, without increasing the cost of simulations, we can marginally get to the point when the addition of a single packet represents a change in the angle-integrated distribution function, at the cost of increased shot noise in the coupling to the fluid. With inelastic scattering and a better treatment of pair processes, we find a reduction in the average energy and total luminosity of heavy-lepton neutrinos, and an increase in the amount of mass ejected -- here by , although on a relatively low amount of total ejected mass . In a separate set of simulations varying the total mass of the binary away from its prompt collapse threshold, we find rapid variations in the amount of ejected matter and in the geometry and composition of the outflows with the total mass of the system. Finally, we use the simulations with our more advanced transport scheme to study in more detail the energy spectrum of neutrinos across the merger remnant.

    Comments:
    25p, 22 figures, version released for comments before journal submission
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    2606.27425 [pdf]
    1 citation
  2. 08

    [Submitted on 25 Jun 2026] (cross-list from gr-qc)

    The crust of dark-matter admixed neutron stars: bulk properties and torsional oscillations

    Jiayi Zhang🇺🇸 · Hector O. Silva🇺🇸

    We study how dark matter (DM) impacts the crust and the spectrum of torsional crust oscillations of dark-matter-admixed neutron stars (DANSs). We construct two-fluid equilibrium solutions wherein baryonic and DM interact gravitationally only, adopting a unified nuclear equation of state for the former and a fermionic equation of state with repulsive self-interaction for the latter. At fixed total gravitational mass and DM mass fraction, we find that DM reduces the crust thickness in comparison to pure baryonic-matter neutron stars (NSs). The thinning of the crust is negligible when most of the DM distribution extends beyond the star's baryonic surface. However, the crust thickness can decrease by as much as 12% when the DM distribution is within the star's baryonic surface, i.e., when the star has a "dark core." We support these results by deriving approximate analytical formulas for the crust thickness that agree with our numerical calculations at the sub-percent level in best case scenarios. Next, we derive the equation that describes crustal torsional modes of DANSs in the relativistic Cowling approximation. We find that the oscillation frequencies are in general higher than those of a comparable pure baryonic-matter NS, with the largest frequency shifts happening in the same parameter space where the crust thickness decreases the most. Moreover, we study the degeneracy between DM and baryonic-crustal microphysics effects on these modes. As an example, we study electron screening, which softens the crust's shear modulus, thus decreasing the frequencies. We find that the degeneracy between the competing effects of DM and electron screening can be broken in some regions of the parameter space we explored. Should they be measured, our results suggest that torsional oscillations could be used to infer the existence of a DM core within massive NSs. (Abridged)

    Comments:
    19 pages, 13 figures, 3 tables
    Subjects:
    General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2606.27456 [pdf]
    0 citations
  3. 09

    [Submitted on 25 Jun 2026] (cross-list from astro-ph.HE)

    Modelling Dissipative Dynamics of r-mode Instability in Hybrid Stars

    Khushbu Zala · Sreemoyee Sarkar

    Compact star cores reach extreme densities and may contain exotic dense-matter phases. Information about the exotic interiors of rapidly rotating pulsars can be inferred from r-mode oscillations, whose stability is governed by viscous dissipation. In this work, we model a compact star containing a possible mixed phase of hadronic and quark matter and employ a hybrid statistical framework based on Bayesian inference to infer the dissipation time scales associated with the hybrid phase. Using low-mass X-ray binaries (LMXB) timing observations together with mass-radius constraints from the Neutron Star Interior Composition Explorer (NICER) mission, we estimate the shear and bulk viscosity contributions to r-mode damping for a hybrid star of two layers. Our inference yields shear and bulk viscous dissipation time scales of s and s respectively. The timescales thus obtained can be implemented to obtain the minima of the star's rotation frequency at Hz at temperature MeV for a hybrid star of mass and Hz at MeV for . We find that the instability window obtained through the inference framework effectively explains the observed stability of millisecond pulsars in both the radio and LMXB populations, particularly for XTE J0929-314 and XTE J1807-294, J0437-4715, J2124-3358, respectively. These results demonstrate that Bayesian inference combined with r-mode phenomenology provides a powerful and observationally consistent framework for constraining the transport properties of dense hybrid matter.

    Comments:
    12 pages, 3 figures
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2606.27465 [pdf]
    0 citations
  4. 10

    [Submitted on 26 Jun 2026] (cross-list from hep-ph)

    From the quark parton model to QCD

    Davison E. Soper🇺🇸

    The quark parton model grew out of deeply inelastic scattering experiments. The parton model developed into a full theory, quantum chromodynamics, QCD. This article explains some of the physics issues encountered in connecting the parton model and QCD.

    Comments:
    37 pages, 8 figures. Submission to Encyclopedia of Nuclear Physics (Elsevier)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2606.27618 [pdf]
    1 citation
  5. 11

    [Submitted on 26 Jun 2026] (cross-list from cond-mat.quant-gas)

    Universality in strongly interacting bosonic clusters

    L. Madeira🇮🇹 · F. Pederiva🇮🇹 · U. van Kolck🇮🇹

    We develop an effective field theory (EFT) for strongly interacting bosonic clusters, using He as a paradigmatic example of universality in systems with large scattering length. At leading order (LO), two- and three-body zero-range interactions are entirely determined by the dimer and trimer ground-state energies. We show that ground-state energies for up to particles converge to cutoff-independent limits with extrapolation coefficients of natural size. At next-to-leading order (NLO), corrections stemming from the two-body interaction range and a four-body force, calibrated to the tetramer ground-state energy, reduce cutoff sensitivity. Close agreement with results from a realistic potential is found at LO and improved at NLO, demonstrating systematic convergence with few parameters at each order. The resulting EFT is directly applicable to larger clusters and bulk helium.

    Comments:
    7+8 pages, 3+8 figures
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); physics.atm-clus (physics.atm-clus)
    arXiv:
    2606.27823 [pdf]
    0 citations
  6. 12

    [Submitted on 26 Jun 2026] (cross-list from hep-lat)

    The QCD phase diagram for three-flavor Möbius domain-wall fermions

    Yu Zhang🇩🇪 · Yasumichi Aoki🇯🇵 · Jishnu Goswami🇩🇪 · Shoji Hashimoto🇯🇵 · Issaku Kanamori🇯🇵 · Takashi Kaneko🇯🇵 · Yoshifumi Nakamura🇯🇵

    We investigate the phase transition of Quantum Chromodynamics (QCD) with three degenerate quark flavors at zero baryon chemical potential. Using Möbius domain-wall fermions as the lattice fermion formulation, we ensure excellent chiral symmetry preservation. Our simulations are performed at three different temporal lattice extents, , with a fixed lattice spacing fm, corresponding to temperatures of 242(4), 181(3), and 121(2) MeV, respectively. We explore a range of quark masses and spatial volumes with aspect ratios spanning from 2 to 4. By analyzing the mass and volume dependencies of the plaquette, plaquette susceptibility, chiral condensate, chiral susceptibilities, and Binder cumulant, we identify the pseudocritical transition quark masses from our largest lattice volumes. For , this is 184(10) MeV (determined from the plaquette susceptibility). For and 12, the transition points vary slightly depending on whether the total or disconnected chiral susceptibility is used, yielding ranges of 36(1)-39.1(9) MeV and 3.5(3)-3.7(2) MeV, respectively, in the scheme at a scale of GeV. The negligible volume dependence at and 8, combined with finite-size scaling analysis at revealing volume growth significantly weaker than expected for a first- or second-order phase transition, points to a continuous crossover at these specific quark mass points. Additionally, we study the effects of residual chiral symmetry breaking on the chiral condensate and chiral susceptibilities using two different values of .

    Comments:
    53 pages, 22 figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2606.28086 [pdf]
    0 citations
  7. 13

    [Submitted on 26 Jun 2026] (cross-list from hep-ph)

    Dense and Cold Magnetized Quark Matter: A Review of Magnetic-Field-Independent Regularization and the Medium Separation Scheme

    Francisco X. Azeredo🇧🇷 · Dyana C. Duarte🇧🇷 · Ricardo L. S. Farias🇧🇷 · Bruno S. Lopes🇧🇷 · João A. R. S. Prado🇧🇷 · William R. Tavares🇧🇷

    We present a comprehensive review of regularization schemes for magnetized dense quark matter within effective models of quantum chromodynamics, focusing on the Magnetic-Field-Independent Regularization (MFIR) and the Medium Separation Scheme (MSS) at finite chemical potential and magnetic field. In nonrenormalizable frameworks such as the Nambu-Jona-Lasinio model, the treatment of ultraviolet divergences is crucial, particularly in magnetized and dense environments where conventional regularization procedures may introduce unphysical artifacts. We show that MFIR consistently isolates divergent vacuum contributions from finite magnetic-field-dependent terms, while MSS extends this separation to the medium sector, ensuring that only vacuum quantities are regularized. Within this unified framework, we analyze the thermodynamics of cold and dense quark matter, including color-superconducting phases, and demonstrate that the superconducting gap remains finite at large chemical potentials, even in the presence of strong magnetic fields. In contrast to results obtained with traditional regularization schemes, we find no evidence for a transition to a normal phase at zero temperature, highlighting the importance of a proper separation between vacuum and medium contributions. These results eliminate spurious oscillations and other nonphysical artifacts, leading to a more robust and physically consistent description of strongly interacting matter under extreme conditions relevant to compact stars and heavy-ion collisions.

    Comments:
    26 pages, 7 figures. Textual corrections, new references added, and two appendices included
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2606.28111 [pdf]
    1 citation

Affiliations

first authorsco-authorsvia INSPIRE