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Nuclear Theory·nucl-th

Tuesday·September 1, 2026

17 papers—7 primary·10 cross-listed

All17Primary7Cross-lists10
  1. 01

    [Submitted on 28 Aug 2026]

    Strongly coupled quark matter in neutron stars and their mergers

    Konstantin Maslov🇺🇸 · Ralf Rapp🇺🇸 · Joaquin Grefa🇺🇸 · Veronica Dexheimer🇺🇸 · Claudia Ratti🇺🇸

    The discovery of the strongly-coupled quark-gluon plasma (sQGP) in high-energy heavy-ion collisions has revealed remarkable properties of matter at high temperature, with transport coefficients close to conjectured bounds from quantum field theory at strong coupling. The high sQGP collision rates imply very large energy uncertainties and the melting of quasiparticle structures. Deploying quantum many-body theory based on the self-consistent -matrix approach for the sQGP at high temperature, we investigate its manifestation at high baryon density and low temperature, as present in neutron stars and their mergers. We constrain the chemical-potential dependence of the quark interaction kernel using first-principles information from Quantum Chromodynamics on baryon-number susceptibilities. Very large collisional widths persist at large density and are found to relegate superconducting phases to rather small temperatures. Instead, a strongly coupled diquark liquid prevails in the thermodynamics under the conditions relevant to neutron-star mergers. At lower densities, the diquarks take over from the single-quark contributions, suggesting a pathway toward hadronization. Our results are consistent with observational constraints on the equation of state of neutron stars, corroborating the presence of strongly coupled quark matter in the interior of these objects.

    Comments:
    7 + 8 (Methods and Extended data) pages, 4 + 7 figures, 2 tables
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2608.28879 [pdf]
    0 citations
  2. 02

    [Submitted on 29 Aug 2026]

    Local-nuclear-density dependent calculation of nucleon electromagnetic form factor ratios in finite nuclei

    G. Ramalho🇰🇷 · K. Tsushima🇧🇷 · Myung-Ki Cheoun🇰🇷

    We calculate the electromagnetic form factors of nucleons bound in finite nuclei and make predictions to the ratio between the electric () and magnetic () form factors in terms of the square of the four-momentum transfer . We extend our previous constant-density calculations within the covariant spectator-QMC framework by incorporating the spatial nuclear density profiles of finite nuclei and quantify the deviations from the average-density approximation used in our previous applications. The impact of the medium effects can then be observed considering the ratio between and the ratio in free space , that define the proton electromagnetic double ratio associated with a given nucleus. The double ratio is expected to remove some systematic uncertainties. There is the expectation that ratios associated with the bound protons inside the nucleus will be measured in the near future in polarization-transfer experiments . Anticipating future measurements on the subject, we make predictions for the double ratios, to be compared with the average measurements on the energy states of protons bound to nuclei. We consider the nuclei C, O and Ca. We conclude that the form factors calculated using nuclear density profile function are less suppressed than in the case of the results calculated using the average nuclear density. The results indicate that the relative importance of the low-density surface region increases with , leading to a weaker suppression than that predicted by the average-density approximation. We also make predictions for the ratios associated with neutrons bound to nuclei.

    Comments:
    16 pages, 6 figures, 4 tables
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2608.29358 [pdf]
    0 citations
  3. 03

    [Submitted on 31 Aug 2026]

    Quantum information in neutron-proton scattering from the matrix

    Linjun Xie · Jinniu Hu · Ying Zhang · Hong Shen

    We study quantum-information aspects of neutron--proton scattering in the spin-space -matrix framework. Four representative classes of input states are considered, namely diagonal mixed states, separable pure states, general two-qubit pure states, and a special Schmidt-like entangled subclass. For each class, ensemble-averaged output mutual information, reduced-state linear entropy, negativity, and geometric quantum discord are calculated in the relative momentum-- scattering angle plane. The results show that the outgoing spin correlations are governed jointly by scattering kinematics and by the structure of the incoming quantum ensemble. Input states with stronger intrinsic coherence or entanglement give larger maxima and higher minima in the mutual information, negativity, and geometric quantum discord. The enhanced regions of the mutual information and geometric discord depend on the input states, while the negativity maximum remains concentrated in the high-momentum backward-scattering region. These results extend earlier studies based on product-state entanglement power and provide an ensemble-based description of how spin correlations in neutron--proton scattering arise from the interplay between input-state structure and scattering dynamics.

    Comments:
    24 pages, 4 figures, 1 table, has been accepted by Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2608.30356 [pdf]
    0 citations
  4. 04

    [Submitted on 31 Aug 2026]

    NS-UNO: Neutron Star EoS Inference from an Unconstrained Number of Observations

    Valéria Carvalho🇵🇹 · Márcio Ferreira🇵🇹 · Michał Bejger🇵🇱 · Constança Providência🇵🇹

    Future multimessenger observations of neutron stars (NS) are expected to substantially increase both the number and precision of astrophysical constraints on the equation of state (EoS) of dense matter. This motivates inference frameworks capable of accommodating a variable, non fixed number of observations while preserving the posterior information associated with each measurement. In this work, we introduce NS-UNO, a Neural Posterior Estimation framework for NS EoS inference designed to accommodate an Unconstrained Number of Observations (UNO). NS-UNO combines a hierarchical DeepSets model with a conditional normalising flow, enabling a single trained model to perform inference from mass-radius observation sets of varying size, with each observation represented by a set of posterior samples. We demonstrate accurate and well calibrated posterior reconstructions using a model trained jointly on piecewise polytropic and non-parametric Gaussian process EoS ensembles. The reconstruction improves as observations probe a broader range of NS masses, while remaining robust to variations in the number and precision of the observations. The model also generalises to EoSs outside the families used during training. Finally, we qualitatively demonstrate the framework on current multimessenger constraints from NICER and GW170817. NS-UNO provides a flexible and scalable approach to NS EoS inference, naturally suited to the increasingly diverse observational datasets expected from next generation multimessenger astronomy.

    Comments:
    15 pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2608.30573 [pdf]
    0 citations
  5. 05

    [Submitted on 31 Aug 2026]

    Production of the and via recombination of jet parton showers in relativistic heavy ion collisions

    Kyong Chol Han🇺🇸 · Sungtae Cho🇰🇷 · Su Houng Lee🇰🇷

    We study the production of the and in heavy ion collisions at TeV by employing two complementary approaches. In the first approach, the production of the and is discussed in the coalescence model. In the second approach, we developed a hybrid framework that combines the recombination of shower and thermal partons with remnant string fragmentation. Thermal partons in the quark-gluon plasma are modeled using a blast-wave parameterization, while the phase space information of medium-modified parton showers is generated from Q-PYTHIA, using unquenched jet partons obtained from HIJING initial inputs. We show that both approaches agree well with the experimental measurements, and demonstrate that this hybrid framework provides deeper insight into the underlying strangeness components in the production of and in relativistic heavy-ion collisions.

    Comments:
    11pages, 9 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.30891 [pdf]
    0 citations
  6. 06

    [Submitted on 31 Aug 2026]

    Effects of isospin imbalance on the chiral phase transition within a Chiral Dual Partner Model

    R. M. Aguirre🇦🇷

    The chiral symmetry is a property of the fundamental theory of the strong interaction that is relevant for the hadronic physics. It is expected that at sufficiently high temperature and matter density, this symmetry becomes manifest. Within the Chiral Dual Partner Model the chiral transformation is implemented in such a way that a fermion mass term is allowed if the parity partner of each baryon is included in the framework. This model is used here to study possible manifestations of the chiral symmetry in dense nuclear matter, assuming constant isospin fraction. It is found that the onset of the odd parity baryons is associated with two branches of thermodynamical instabilities, one of them leads to a first order phase transition for temperatures below MeV. An analysis of these instabilities in the phase space is given, and neutron star matter is considered as a special case.

    Comments:
    14 pages 11 figs
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2608.30936 [pdf]
    0 citations
  7. 07

    [Submitted on 31 Aug 2026]

    Electromagnetic responses induced by one- and two-body nuclear currents in inclusive electron-nucleus scattering

    Kajetan Niewczas · Ashish Kumar Jha · Raúl González-Jiménez · Natalie Jachowicz · Alexis Nikolakopoulos · Jan Ryckebusch

    The longitudinal and transverse nuclear response functions encode information about the electromagnetic behavior of the nuclear target probed in inclusive electron-nucleus scattering. We present a microscopic calculation based on an independent-particle model, where a non-relativistic nuclear mean-field potential governs both the initial and final hadronic states of the interaction. We add dynamically generated short-range nucleon-nucleon correlations (SRCs), as well as meson-exchange currents (MECs) derived from one-pion exchange and intermediate -resonance excitation. We evaluate the contributions from one- and two-nucleon knock-out reactions to nuclear responses in inclusive electron scattering from in the quasielastic and dip regions. We demonstrate that for quasielastic kinematics, SRCs quench both nuclear responses, while the MECs enhance the transverse signal, substantially improving the predicted transverse-to-longitudinal ratio. In the dip region between the quasielastic and the -resonance peaks, we find that the observed excess of transverse strength originates mainly from explicit two-nucleon knock-out following a -resonance excitation.

    Comments:
    23 pages, 19 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.31044 [pdf]
    0 citations

Affiliations

first authorsco-authorsvia INSPIRE