Nuclear Theory·nucl-th

Thursday·May 28, 2026

13 papers—9 primary·4 cross-listed

01
Projection operator onto spin-S eigenspaces of total and orbital angular momenta
M.I. Krivoruchenko
The Frobenius covariant is used to construct a projection operator onto the spin-S eigenspaces associated with the squares of the total and orbital angular momenta. The covariant admits two equivalent representations: as a polynomial in powers of the scalar product of the spin and orbital angular momentum operators, and as a finite expansion in terms of their respective polarization operators. A correspondence is established with Villars' angular momentum projection, used in nuclear structure studies.
nucl-thquant-phZh.Eksp.Teor.Fiz.(2026)·0 citations
02
Light nuclear scattering from neural quantum states
Scott Lawrence · Yukari Yamauchi
We present a method of studying few-body nuclear scattering by means of neural quantum states, without requiring time-evolution. A recently developed family of stable minimum principles for Schrodinger's equation provides conservative uncertainties on cross sections and partial wave amplitudes computed in this way. We use this method to study both elastic and inelastic neutron-deuteron scattering with realistic nuclear two-body forces.
nucl-thquant-ph0 citations
03
A Question of Shape: New Mechanism Governing Superheavy Nuclei Survival
A. Rahmatinejad · T. M. Shneidman · G. G. Adamian · N. V. Antonenko · P. Jachimowicz · M. Kowal
We demonstrate that hot superheavy nuclei do not retain spherical shapes, as traditionally assumed, but instead equilibrate in deformed, often oblate or triaxial, configurations at finite excitation energy. This behavior arises from a mechanism analogous to the Jahn-Teller effect: spherical systems exhibit high single-particle degeneracy near the Fermi surface, causing their shell corrections to damp out significantly faster with temperature than those of deformed shapes. Using a finite-temperature framework, we reveal a thermally induced inversion of the potential-energy landscape in the Z = 118-120 region, where deformed minima become energetically favored at U = 30-50 MeV. This shape inversion fundamentally alters the competition between neutron evaporation and fission. We derive a deformation-dependent correction to the survival probability, revealing a systematic bias in estimates based on spherical ground-state properties. Our results identify a finite-temperature structural effect that calls for a revision of current models of superheavy-nucleus synthesis and decay.
nucl-th0 citations
04
Pion off-shell form factors
S. G. Bondarenko🇷🇺 · M. K. Slautin🇷🇺
In the paper, the electromagnetic off-shell pion form factors in the Bethe-Salpeter formalism with a separable kernel are considered. Different types of vertex functions of a pion are investigated. The separable kernel of the quark-antiquark interaction is used to obtain an analytical solution of the equation. The pion constants and the form factors on both the on-shell and off-shell surfaces are calculated. The differential cross section of the reaction $^{1} H (e, e^{'} π^{+}) n$ is also calculated in the paper. All the obtained results are compared with experimental data. The fulfillment of the Ward-Takahashi identity for the off-shell form factors $F_{1} (Q^{2}, t)$ and $F_{2} (Q^{2}, t)$ of a pion is verified.
nucl-th0 citations
05
Estimation of potential radius based on momentum distribution of a constituent particle
Eisuke Kawamura🇯🇵 · Kotaro Murakami🇯🇵 · Daisuke Jido🇯🇵
We propose using the potential radius as a probe of the structure of hadrons, particularly to classify exotic hadrons as hadronic or quark composite states.In this study, we focus on the radius of the effective potential felt by each constituent particle. Using a simple model with a square-well potential, we demonstrate that the potential radius can be estimated from the momentum distribution of a constituent particle not only for deeply bound states but also for shallowly bound states.We find that the momentum-based quantity provides a more robust estimate of the potential radius in the shallow-binding regime.This is because the momentum-based length scale decreases to zero as the potential radius vanishes, whereas the RMS radius approaches a finite value set by the binding energy.As a result, the momentum distribution avoids the finite-intercept problem that can make the inverse estimate of the potential radius ill-defined.With future experimental data on the momentum distribution of the constituent nucleon in $K N N N$ production at J-PARC, the potential radius may be determined within the present framework.
nucl-thJ.Subatomic Part.Cosmol.(2026)·0 citations
06
Formation of bound composite vortices of a singly-quantized $^{1}$ S $_{0}$ vortex and half-quantized $^{3}$ P $_{2}$ vortices in the $^{1}$ S $_{0}$ - $^{3}$ P $_{2}$ coexisting phase in neutron stars
Tatsuhiro Hattori · Muneto Nitta · Kazuyuki Sekizawa
Pulsar glitches are believed to originate from the dynamics of quantized vortices in the neutron superfluid interior. The outer core of a neutron star hosts a $^{3} P_{2}$ spin-triplet superfluid, whose half-integer quantum vortices (HQVs) are qualitatively different from the $^{1} S_{0}$ singly quantized vortices (SQVs) in the inner crust. It has recently been proposed that the coupling between these two vortex species gives rise to a large-scale vortex network, providing a candidate mechanism for the diversity of observed pulsar glitch phenomena. Using the Gross--Pitaevskii equations for the $^{1} S_{0}$ and $^{3} P_{2}$ condensates, we perform two-dimensional simulations of one SQV and two HQVs in a coexistence phase near the crust-core boundary, varying the density--density and Josephson coupling constants. We find that the Josephson term, arising from the relative phase between the two condensates, induces a strong attractive interaction between the two HQVs and the SQV, which dominates over the density--density coupling. When pinning potentials are applied to the HQVs and the SQV at spatially separated locations, this attraction is found to be sufficiently strong to drive vortex depinning. These results suggest that two HQVs and one SQV can form a tightly bound composite vortex at the crust-core boundary, with implications for the glitch mechanism in neutron stars.
nucl-thastro-ph.HEcond-mat.quant-gas2 citations
07
Impact of hyperon mixing on neutron star structure based on Skyrme-type equations of state: Systematic analysis of $Λ N N$ and $ΛΛ N$ three-body forces with Bayesisan inference
Taeho Lee🇯🇵 · Yoonhak Nam🇯🇵 · Kazuyuki Sekizawa🇯🇵
We study hyperonic density-dependent three-body effects in cold neutron-star matter using a Skyrme energy-density-functional framework. In beta-equilibrated $n p e μ Λ$ matter, the effective $Λ N N$ and $ΛΛ N$ terms are varied separately in the $(β, A_{3})$ and $(γ, C_{3})$ planes, and each tabulated equation of state is used in Tolman--Oppenheimer--Volkoff calculations. The calculated $P$ -- $ε$ branches are classified by monotonicity and extremum structure. The $ΛΛ N$ term does not affect the $Λ$ -onset condition, but modifies the finite- $Λ$ post-onset EOS: increasing $C_{3}$ generally stiffens the post-onset branch and raises $M_{m a x}$ in mechanically admissible regions, whereas increasing $γ$ reduces this enhancement at fixed $C_{3}$ . In contrast, the $Λ N N$ term shifts the $Λ$ -onset density and modifies the post-onset EOS simultaneously, producing organized branch-limited and Maxwell-candidate regions for some reference interactions. Representative two-extrema cases are examined with Maxwell constructions. We also perform an exploratory Bayesian analysis using neutron-star mass--radius information alone and apply XGBoost--SHAP surrogate diagnostics to summarize parameter sensitivities. Within the adopted likelihood and prior ranges, the posterior weight tends to favor sizable hyperonic three-body repulsion, and the SHAP analysis identifies $A_{3}$ and $C_{3}$ as important controls of $M_{max}$ and $R_{2.0}$ . These results show that maximum-mass recovery in hyperonic neutron stars is not a single mechanism: $M_{max}$ maps must be interpreted together with onset behavior, branch admissibility, and extremum-count diagnostics. *shortened due to the arXiv's word limit.
nucl-thastro-ph.HE1 citation
08
Three-dimensional orbital-free density functional theory description of nuclear pasta in the inner crust of neutron stars
Yo Nakamura · Kazuyuki Sekizawa
Background: In the bottom layer of the inner crust of neutron stars, various crystalline structures are expected to emerge that are collectively called ``nuclear pasta.'' It is desirable to know properties of nuclear pasta in a wide variety of conditions for astrophysical applications. However, three-dimensional fully-microscopic calculations require huge computational effort that makes it still challenging to carry out systematic calculations. Purpose: In this paper, we propose an efficient method to calculate various nuclear pasta configurations in a non-empirical manner, based on three-dimensional orbital-free density functional theory (OF-DFT). We demonstrate the feasibility of the proposed approach by applying it to densities across the inner crust of neutron stars. Methods: As a first application of OF-DFT for nuclear pasta, we employ the second-order extended Thomas-Fermi (ETF) expansion of Skyrme energy density functional (EDF) to construct an EDF that depends only on neutron and proton number densities. Based on the variational principle, we derive Euler-Lagrange equations to determine optimal neutron and proton density distributions and solve them self-consistently. In this work, we call this approach the self-consistent ETF (SC-ETF) method. Results: We perform three-dimensional SC-ETF calculations with various box sizes. We successfully obtain various pasta structures, depending on given average nucleon number densities, consistent with earlier studies. Moreover, we find other exotic structures, such as bending and/or connected rods, slabs with a hole, etc., underlining the advantage of the self-consistent formalism. Conclusions: We demonstrate that the SC-ETF method proposed in this study, which can be regarded as a realization of OF-DFT, is a promising tool that can efficiently describe complex pasta structures without empirical assumptions on geometric shapes.
nucl-thastro-ph.HEcond-mat.quant-gas0 citations
09
Quantum effects in the quadrupole rotor picture of ultra-relativistic ion-ion collisions
Stavros Bofos🇫🇷 · Yi Li🇨🇳 · Chenrong Ding🇨🇳 · Benjamin Bally🇩🇪 · Thomas Duguet🇫🇷 · Mikael Frosini🇫🇷 · Jiangming Yao🇨🇳
The azimuthal hadronic flow observed in ultra-relativistic ion-ion collisions provides a sensitive probe of many-body ground-state correlations in the colliding nuclei. In particular, collective correlations associated with nuclear "intrinsic deformation" are expected to leave pronounced fingerprints on specific final-state observables. However, such effects are commonly interpreted within a classical rigid-rotor picture, despite the intrinsically quantum nature of nuclei. In this Letter, the validity of this interpretation is assessed systematically across the nuclear chart by comparing the quantum quadrupole rotor with its classical rigid-rotor limit. Quantum contributions associated with the fermionic nature of the nucleons are shown to be largely independent of shell effects, and hence of the intrinsic deformation. While they account for nearly all of the quantum rotor effective quadrupole deformation in light and/or spherical nuclei, they drop below 10% in intrinsically well deformed heavy nuclei. The present letter demonstrates that a quantitative interpretation of nuclear-structure effects in final-state observables requires going beyond the classical rigid-rotor paradigm. Beyond the quantum contributions quantified presently, correlations associated with collective vibrations and with the non-collective nucleonic motion must be further included and characterized.
nucl-thhep-phnucl-ex5 citations

Affiliations

first authorsco-authorsvia INSPIRE