Nuclear Theory·nucl-th

Monday·June 29, 2026

13 papers—6 primary·7 cross-listed

01
Single- and Double- $Λ$ Hypernuclear Correlations Calibrate $ΛΛ$ Interaction Energies
Shi Yuan Ding · Bao Yuan Sun
Double- $Λ$ hypernuclei are essential for probing the $ΛΛ$ interaction in the double-strangeness $S = - 2$ sector, yet the scarcity of experimental data severely limits systematic predictions. We present an evaluation framework based on nuclear many-body theory that exploits the intrinsic structural similarity between single- $Λ$ and double- $Λ$ systems to transfer empirical constraints from the well-mapped $S = - 1$ sector to the $S = - 2$ sector. By analyzing theoretical deviations of binding energies in light single- and double- $Λ$ hypernuclei, we identify a robust linear correlation between two sectors. This correlation enables a statistical evaluation of double- $Λ$ separation energies ( $B_{ΛΛ}$ ) and $ΛΛ$ interaction energies ( $Δ B_{ΛΛ}$ ) for heavier double- $Λ$ hypernuclei, by drawing on a wealth of empirical data from the single- $Λ$ sector with quantified uncertainties. Our results show that evaluated $Δ B_{ΛΛ}$ values, while consistent with existing data, are systematically larger than direct relativistic density functional predictions constrained only by the NAGARA event. This discrepancy suggests that standard mean-field-based extrapolations may underestimate $ΛΛ$ correlations and other many-body effects, motivating an evaluation-based correction that offers crucial benchmarks for future $S = - 2$ experiments at facilities such as HIAF and J-PARC.
nucl-th0 citations
02
Oblate-prolate shape mixing and E0 transition in 28Si
Yasutaka Taniguchi · Masaaki Kimura
Background: oblate-prolate shape coexistence in $^{28}$ Si has been discussed for decades, but the degree of shape mixing between these configurations remains poorly constrained. Purpose: We constrain the oblate-prolate mixing amplitudes in $^{28}$ Si using available experimental information and discuss the inter-band E0 transition strength. Methods: Oblate and prolate $0^{+}$ and $2^{+}$ configurations are obtained by antisymmetrized molecular dynamics combined with the generator coordinate method. Using these configurations as the basis states, we constrain the mixing amplitudes by simultaneously reproducing the measured charge radius, the quadrupole moment of the $2_{1}^{+}$ state, and the in-band and inter-band $B (E2)$ values. The strength of the density-dependent term in the Gogny interaction is also varied within a reasonable range. Results: In the ground state, the oblate component is dominant, and the prolate component in the ground state is limited to less than about $20%$ . For the $2_{1}^{+}$ state, the allowed prolate component is smaller than that in the ground state. The present analysis does not tightly constrain the corresponding E0 transition strength, but an upper limit of $ρ^{2} (E0; 0_{3}^{+} \to 0_{1}^{+}) ≲ 0.206$ is obtained. Conclusions: The low-lying $0^{+}$ states of $^{28}$ Si may exhibit substantial oblate-prolate mixing. A measurement of the inter-band E0 transition strength would provide a quantitative determination of the mixing amplitude.
nucl-thnucl-ex1 citation
03
Universal EOS-Radius Inverse Mappings Govern Precision-Dependent Inference of the Neutron Star Equation of State
Bao-An Li
Bayesian inference of the neutron star (NS) equation of state (EOS) generally assumes that improved observations primarily reduce posterior uncertainties while leaving inferred EOS parameters unchanged. Using mock measurements of the radius of a canonical $1.4 M_{⊙}$ NS with identical central values but varying observational precisions, we show that the inferred posterior means of EOS parameters can shift systematically as the measurement uncertainty changes. We demonstrate that this behavior originates from previously unidentified nearly universal inverse mappings between the NS radius $R_{1.4}$ and empirical EOS parameters. Across a broad range of observational precisions, posterior samples collapse onto nearly unique functions. These mappings are largely independent of observational precision and define a low-dimensional EOS manifold underlying Bayesian inference. We show that the precision dependence of inferred EOS parameters arises from nonlinear filtering of the posterior radius distribution through these mappings. In the narrow-distribution limit this effect reduces to a Jensen-type correction proportional to the local curvature of the inverse mapping, while for presently realistic uncertainties the full nonlinear-filtering relation accurately reproduces the posterior means. Our results reveal a geometric origin of precision-dependent inference in NS EOS studies and provide a new framework for connecting astrophysical observations directly to microscopic nuclear many-body theories.
nucl-thastro-ph.HEhep-phhep-th+12 citations
04
Efficient calculation of two-neutrino double-beta-decay nuclear matrix elements
Mihai Horoi🇺🇸
Reliable nuclear matrix elements (NMEs) are essential for interpreting double-beta-decay experiments and for connecting measured or constrained half-lives to the underlying weak-interaction physics. The two-neutrino mode ( $2 ν β β$ ) is allowed by the Standard Model and has been observed in several nuclei, whereas the neutrinoless mode ( $0 ν β β$ ) remains the key experimental signature of lepton-number violation and Majorana neutrino masses. Recent statistical shell-model studies indicate a strong correlation between the $2 ν β β$ and $0 ν β β$ NMEs, making accurate and efficient calculations of the former especially useful for assessing the latter. Direct evaluations of $2 ν β β$ NMEs usually require summing over many $1^{+}$ states in the intermediate odd-odd nucleus, a procedure that becomes expensive and may converge slowly in large model spaces. We present and test an improved strength-function method based on Lanczos iterations that avoids full diagonalization while preserving the accuracy of explicit summation where such benchmarks are possible. The method is applied to several experimentally important emitters and to different effective Hamiltonians. We also show that the same framework can be used for the higher-order NMEs entering Taylor-expanded phase-space treatments of $2 ν β β$ and related decay modes.
nucl-thhep-ph0 citations
05
QCD critical surface from constant entropy contours
Hitansh Shah🇺🇸 · Tristan Gyure🇺🇸 · Anabella Leon🇺🇸 · Francesco Di Clemente🇺🇸 · Mauricio Hippert🇧🇷 · Claudia Ratti🇺🇸 · Volodymyr Vovchenko🇺🇸
We provide the first mapping of the critical surface in (2+1)-flavor QCD in the full $(T, μ_{B}, μ_{Q}, μ_{S})$ space, anchored on lattice QCD results at vanishing chemical potentials and obtained within an expansion along contours of constant entropy density. In the pure $μ_{B}$ direction, this framework yields a critical point at $(T_{c}, μ_{B, c}) ≃ (114, 602)$ MeV. Here we extend the construction to arbitrary directions in the three-dimensional chemical-potential space, parametrized by spherical coordinates $(μ, θ, φ)$ , with the radial expansion truncated at $O (μ^{2})$ . The resulting two-dimensional surface carries a direction-dependent critical temperature $T_{c} (θ, φ)$ and baryochemical potential $μ_{B, c} (θ, φ)$ , which quantify the shift of the critical point relative to the pure $μ_{B}$ direction. We find that $μ_{B, c}$ increases by 40-100 MeV along the approximately strangeness neutral direction [ $μ_{S} \approx (0.15$ -- $0.33) μ_{B}$ , $μ_{Q} \approx 0$ ] relevant for heavy-ion collisions, while the critical temperature stays essentially unchanged. In the charge-neutral, weak-equilibrium direction~[ $μ_{Q} \approx - (0.05$ -- $0.1) μ_{B}$ , $μ_{S} = 0$ ] relevant for neutron star mergers, the critical point, and the associated first-order phase transition, remain present at essentially the same location in the $(T, μ_{B})$ plane. We find no evidence for a critical point at large isospin densities, $∣ μ_{Q} ∣/ μ_{B} ≳ 1$ , relevant for cosmic trajectories in the early Universe, nor along the pure electric-charge or strangeness directions, at least outside the regions where pion or kaon condensation may occur.
nucl-thhep-ph0 citations
06
Bridging Ab Initio Symmetries and Global Nuclear Masses with Interpretable Neural Networks
Phong Dang · Evander Espinoza · Xiaoliang Wan · Michela Negro · Jerry P. Draayer · Feng Pan · Tomas Dytrych · Daniel Langr · David Kekejian
Ab initio modeling has established Wigner's SU(4) and Elliott's SU(3) as dominant symmetries of the nuclear force in light and intermediate-mass nuclei. We ask whether they also govern nuclear binding across the entire chart. Our aim is not high-precision prediction but physical insight, through interpretable, symmetry-based models. From the SU(3) and SU(4) Casimir operators we construct three neural-network (NN) mass models: Feature-Informed NN (FINN) for point predictions, Gaussian-Informed NN (GINN) adding uncertainty quantification, and Wigner-Informed NN (WINN) -- a mass formula using the Casimirs as an operator basis. All are trained on AME2016 and validated on nuclei new to AME2020. The SU(4) operators alone cut the root-mean-square error (RMSE) by nearly half on train and test data, and by about a fifth on extrapolation, relative to the liquid-drop baseline -- showing that Wigner's symmetry carries predictive information beyond bulk properties. Despite its compact form, WINN reaches the lowest validation RMSE, 0.430 MeV -- competitive with state-of-the-art mass models -- which we read less as a benchmark than as evidence that its symmetry basis captures important physics. WINN further reveals i) an enhancement of the quadratic SU(4) Casimir near the neutron dripline, signaling restoration of Wigner's symmetry, and ii) an unexpected gain of the quartic operator in the superheavy region. We thereby elevate emergent symmetries from the hidden order within individual nuclei to a governing principle of the whole nuclear chart.
nucl-thcs.LG0 citations
07
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 $Δ f_{ν} < 1$ 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 $50%$ , although on a relatively low amount of total ejected mass $< 0.005 M_{⊙}$ . 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.
↳ astro-ph.HEgr-qcnucl-th1 citation
08
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)
↳ gr-qcastro-ph.HEhep-phnucl-th0 citations
09
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 $τ_{s} = (4.9 9_{- 0.52}^{+ 0.49}) \times 1 0^{8} T^{\frac{5}{3}}$ s and $τ_{B} = (2.15 0_{- 0.60}^{+ 1.23}) \times 1 0^{19} (T^{4} 1 0^{- 12} + T^{2} 1 0^{- 6})^{- 1} Ω^{- 2}$ s respectively. The timescales thus obtained can be implemented to obtain the minima of the star's rotation frequency at $Ω = 451.87$ Hz at temperature $T = 0.259$ MeV for a hybrid star of mass $1.5$ $M_{⊙}$ and $Ω = 517.47$ Hz at $T = 0.234$ MeV for $M = 1.75 M_{⊙}$ . 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.
↳ astro-ph.HEhep-phnucl-th0 citations
10
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.
↳ hep-phnucl-th1 citation
11
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 $^{4}$ 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 $N = 15$ 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.
↳ cond-mat.quant-gasnucl-thphysics.atm-clus0 citations
12
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, $N_{t} = 6, 8, 12$ , with a fixed lattice spacing $a = 0.1361 (20)$ 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 $N_{s} / N_{t}$ 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 $N_{t} = 6$ , this is 184(10) MeV (determined from the plaquette susceptibility). For $N_{t} = 8$ 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 $MS$ scheme at a scale of $μ = 2$ GeV. The negligible volume dependence at $N_{t} = 6$ and 8, combined with finite-size scaling analysis at $N_{t} = 12$ 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 $L_{s}$ .
↳ hep-lathep-phhep-thnucl-th0 citations
13
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.
↳ hep-phhep-lathep-thnucl-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE