Nuclear Theory·nucl-th

Wednesday·April 15, 2026

9 papers—3 primary·6 cross-listed

01
Parameter-free deformation variables of the proxy-SU(3) symmetry in even-even atomic nuclei with Z=28-82, N=28-126
Dennis Bonatsos · V. K. B. Kota · Andriana Martinou · S. K. Peroulis · D. Petrellis · P. Vasileiou · T. J. Mertzimekis · N. Minkov
The proxy-SU(3) approximation to the shell model, which restores the SU(3) symmetry of the 3-dimensional harmonic oscillator beyond the sd shell, predicts the collective deformation variables beta and gamma of even-even atomic nuclei in a parameter-free way, based on the most symmetric irreducible representation (irrep) of SU(3) allowed by the Pauli principle and the short-range nature of the nucleon-nucleon interaction, which in group theoretical language is the highest weight (hw) irrep. In the few cases in which the hw irrep turns out to be completely symmetric, thus being able to accommodate only the ground state band, the next hw (nhw) irrep becomes indispensable. In the present article complete tables of the hw and nhw irreps are given for all atomic nuclei ranging from Z=28, N=28 to Z=82, N=126, along with the corresponding parameter-free predictions for the deformation variables beta and gamma. A few examples using the tabulated results for providing microscopic insight for specific effects in various regions of the nuclear chart are also given.
nucl-th0 citations
02
Symplectic no-core configuration interaction framework for nuclear structure
Anna E. McCoy · Mark A. Caprio · Patrick J. Fasano · Tomas Dytrych
We present the symplectic no-core configuration interaction (SpNCCI) framework, in which the nuclear many-body problem is solved a symmetry-adapted basis that explicitly encodes approximate symmetries associated with nuclear collectivity and deformation. In this framework, calculations are carried out in a basis organized into Sp(3,R) irreducible representations (irreps), each of which can be expressed as an infinite tower of U(3) irreps. In this framework, matrices of realistic relative two-body operators, such as the nuclear Hamiltonian, are computed directly in the Sp(3,R) many-body basis, obviating the need to expand all Sp(3,R) many-body states in, e.g., a U(3)-coupled configuration basis. Instead, many-body matrix elements are obtained via a recurrence relation that expresses a given matrix element in terms of matrix elements between basis states with fewer oscillator quanta. To use this recurrence method for computing matrix elements of relative two-body operators, we must first expand each operator into components of U(3) tensors. To this end, we present a method for decomposing arbitrary operators into U(3) tensor components.
nucl-th1 citation
03
Dynamics of density fluctuations in atomic nuclei
Francesca Bonaiti · Gaute Hagen · Thomas Papenbrock
We study the spatiotemporal patterns of density fluctuations in $^{16, 24}$ O and $^{48}$ Ca using nuclear interactions from chiral effective field theory and the time-dependent coupled-cluster method. We find that two-particle-two-hole excitations generate small-amplitude fluctuations that are fast, short-ranged and of stochastic character.
nucl-thnucl-exPRL(2026)·0 citations
04
Finite temperature effects on g-modes of inviscid neutron stars
David Morales-Zapien · Prashanth Jaikumar · Thomas Klähn
We study the effect of temperature on secular, compositional $g$ -modes in the core of inviscid neutron stars. Using a chiral $S U (2)_{f}$ sigma model, we construct isentropic temperature profiles for hot and dense matter and find that the frequency of the global core $g$ -mode's dependence on temperature is governed by the nuclear symmetry energy slope parameter $L$ . As a result, the $g$ -mode frequency of a warm neutron star can be either higher or lower than that of its cold counterpart, depending on $L$ . Our results highlight the interplay of thermal effects and composition gradients, and demonstrate the potential of neutron star $g$ -mode observations to constrain the density dependence of the symmetry energy.
↳ astro-ph.HEastro-ph.SRnucl-th0 citations
05
Effect of $K^{*}$ meson magnetic dipole moment on the $e^{+} e^{-} \to K^{+} K^{-} π^{0} π^{0}$ cross section
Luis A. Jiménez Pérez🇲🇽 · Antonio Rojas🇲🇽 · Genaro Toledo🇲🇽
We explore the sensitivity of the $e^{+} e^{-} \to K^{+} K^{-} 2 π^{0}$ cross section to the magnetic dipole moment (MDM) of the $K^{*}$ vector meson. We describe the $γ^{*} \to 2 K 2 π$ vertex using a vector meson dominance model, including the intermediate resonant contributions relevant for energies below 2.4 GeV. Using BaBar data for this process, we show that this observable is indeed sensitive to the MDM of the $K^{*}$ ; we obtain a central value for the MDM of $μ_{K^{*}} = 4.5$ and an upper bound of $μ ˉ_{K^{*}} = 6.3$ , in units of $e /2 m_{K^{*}}$ . We emphasize the need for higher precision data to provide a first data-driven determination of this parameter to confront it with theoretical predictions.
↳ hep-phnucl-thPRD(2026)·0 citations
06
Spherical-tensor description of the Jahn--Teller--Hubbard molecule and local electron--phonon entanglement
Koichiro Takahashi · Shuichiro Ebata · Naotaka Yoshinaga · Shintaro Hoshino
We investigate the localized-electron character of the Mott-insulating phase in A $_{3}$ C $_{60}$ using a single-site multiorbital electron model coupled to anisotropic molecular vibrations (Jahn--Teller phonons). We apply the spherical-tensor formalism, a framework originally developed in nuclear physics, to analyze the electron--phonon-coupled ground-state multiplet. Focusing on multipole moments, we find that both the conventional electronic quadrupole moment and the lattice displacement associated with the molecular vibrations vanish, even though the degenerate ground-state multiplet implies the presence of quadrupolar degrees of freedom. By analyzing these degrees of freedom within the spherical-tensor framework, we introduce composite (two-body) quadrupole operators involving both electrons and phonons and study their parameter dependence numerically. Furthermore, using quasispin selection rules, we demonstrate that the composite quadrupole does not couple to either the conventional quadrupole or lattice-displacement operators, thereby distinguishing it fundamentally from standard quadrupolar degrees of freedom. In addition, we investigate the nature of the electron--phonon entanglement and characterize it from the viewpoint of angular momentum. Analysis of the entanglement spectrum reveals that the ground state consists of superpositions of multi-phonon states with angular momenta $L_{ph} = 2$ and $L_{ph} = 3$ , formed through coupling to three-electron states with $L = 1$ and $L = 2$ .
↳ cond-mat.str-elnucl-th0 citations
07
Scattering Faddeev calculations in the double continuum
Romain Guérout🇫🇷
We use the configuration-space Faddeev formalism to study scattering of three particles in the double continuum where all particles are free. All scattering processes, starting from and ending in both single and double continua, are collected in a unique matrix. We apply our method to the benchmark system of neutron-deuteron scattering.
↳ quant-phnucl-thComptes Rendus Physique(2026)·0 citations
08
Open-flavor threshold effects on quarkonium spectrum in the BOEFT
Nora Brambilla🇩🇪 · Abhishek Mohapatra🇩🇪 · Tommaso Scirpa🇩🇪 · Antonio Vairo🇩🇪
The impact of open-flavor thresholds on the quarkonium spectrum has been a subject of study since the introduction of the Cornell potential and has been quantified through various phenomenological approaches, most notably the $^{3} P_{0}$ model. We revisit this problem using the Born--Oppenheimer effective field theory (BOEFT), an effective field theory systematically derived from QCD by exploiting hierarchies of energy scales and symmetries. Within the BOEFT, open-flavor threshold effects emerge from the mixing between quarkonium and tetraquark static potentials sharing the same Born--Oppenheimer quantum numbers. The shapes of the static potentials are constrained by lattice QCD calculations. Furthermore, we account for the distinctive behavior of the BOEFT tetraquark static potentials at short and large distances: at short distances they are repulsive, reflecting the color-octet configuration of the heavy quark-antiquark pair, while at large distances they asymptotically approach heavy-light meson-antimeson thresholds. To quantify threshold effects on the quarkonium spectrum below threshold, we solve a set of coupled Schrödinger equations dictated by the BOEFT, whose only free parameter, the adjoint meson mass, is fixed to the mass of the $χ_{c 1} (3872)$ state. These coupled equations are solved both in the spin-isospin averaged threshold limit and, for the first time, including the spin splittings of the physical thresholds. We validate our results by computing the same threshold effects as self-energy corrections to the quarkonium propagator. We compare our predictions with existing experimental data and previous literature. Finally, we provide a field-theoretical interpretation of the pair-creation constant $γ$ appearing in the $^{3} P_{0}$ model.
↳ hep-phhep-exhep-latnucl-th4 citations
09
Hydrodynamic Initial Conditions in Small Systems from Proton Phase-Space Entropy
Gabriel Rabelo-Soares🇧🇷 · Gojko Vujanovic🇨🇦 · Giorgio Torrieri🇧🇷
The experimental observation of collective behaviour in proton-proton and proton-nucleus collisions poses a fundamental theoretical question regarding the proper characterization of the initial state underlying hydrodynamic evolution. While relativistic hydrodynamics requires an initial condition (IC) characterized by an entropy current, corresponding to a maximally mixed state, the microscopic description of the proton is based on inherently quantum objects, that are projections of pure states. We show that the appropriate matching between proton wave function and classical hydrodynamics emerges from the coarse-graining of its phase-space distribution quantified by the Wehrl-like entropy. This entropy provides a semi-classical, positive-definite measure of the density of accessible microstates at a given resolution scale, and therefore constitutes the appropriate quantity to characterize entropy deposition in small collision systems.
↳ hep-phnucl-thJ.Subatomic Part.Cosmol.(2026)·0 citations

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