Nuclear Theory·nucl-th

Wednesday·November 26, 2025

10 papers—5 primary·5 cross-listed

06
[Submitted on 24 Nov 2025] (cross-list from gr-qc)
Universal Relations with Dynamical Tides
Jayana A. Saes🇺🇸 · Abhishek Hegade K. R.🇺🇸 · Nicolás Yunes🇺🇸
Observations of neutron stars and the precise measurement of their macroscopic properties have provided valuable insights into fundamental physics, both by constraining the behavior of nuclear matter under extreme conditions and by enabling tests of general relativity in the strong-field regime. In this context, equation-of-state-insensitive or ``quasi-universal'' relations between key observables, such as the compactness, dimensionless static tidal deformability, and moment of inertia, play a crucial role in connecting different measurable observables while minimizing uncertainties due to the yet unknown equation-of-state. In this work, we identify new quasi-universal relations between the static, dimensionless tidal deformability ( $Λ^{(0)}$ ) and its leading-order dynamical correction ( $Λ^{(2)}$ ), as well as between $Λ^{(0)}$ and a combination of these parameters ( $Λ^{(0)} / Λ^{(2)} \equiv M ω_{*}$ ), obtained from the small-frequency expansion of the relativistic tidal response. We test these relations across a representative set of 59 equations of state, finding that the equation-of-state dependence does not exceed $\sim$ 5\% for the $Λ^{(0)}$ -- $Λ^{(2)}$ relation and $\sim 2.8%$ for the $Λ^{(0)}$ -- $M ω_{*}$ relation. This indicates a high degree of universality and offers a simplified framework for incorporating dynamical tidal effects into gravitational-wave modeling. Furthermore, we compare the dynamical tidal response against different recent strategies (a Taylor expansion and a one-mode approximation) to model the dynamical tide. We find that both models are capable of capturing the frequency-dependent behavior of the dynamical tidal deformability, with the one-mode approximation agreeing better with the dynamical response than the Taylor expansion in most of the parameter space.
Comments:
15 pages, 8 figures
Subjects:
General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2511.19626 [pdf]
PRD(2026)·7 citations
07
[Submitted on 25 Nov 2025] (cross-list from hep-ph)
First determination of fragmentation functions in an exotic-hadron candidate
S. Kumano🇨🇳
In recent years, there are experimental reports on exotic-hadron candidates, which have different quark configurations from ordinary $q q ˉ$ and $q q q$ constituents. However, it is not easy to confirm their exotic nature from global observables such as masses, spins, parities, and decay widths. At high energies, internal quark and gluon configurations could become more apparent because hadrons should be described by fundamental degrees of freedom of quarks and gluons in quantum chromodynamics. One of such possibilities is to use the fragmentation functions (FFs). In this work, accurate FFs of an exotic hadron candidate $f_{0}$ (980) are determined for the first time by an global analysis of experimental data on $e^{+} + e^{-} \to f_{0} (980) + X$ with recent precise measurements of the Belle collaboration. From the global analysis, we found that their second moments have a relation $M_{u} = M_{d} ≪ M_{s} \sim M_{g}$ for up-quark, down-quark, strange-quark, and gluon FFs. Furthermore, the function $D_{s}^{f_{0}} (z)$ is distributed in the larger- $z$ region in comparison with the functions $D_{u}^{f_{0}} (z)$ , $D_{d}^{f_{0}} (z)$ , and $D_{g}^{f_{0}} (z)$ . These facts support that the $f_{0} (980)$ has the $s s ˉ$ configuration at high energies. This is a new finding that $f_{0} (980)$ should be considered mainly as the $s s ˉ$ state, which is different from our usual understanding as a tetraquark (or $K K ˉ$ ) hadron from low-energy studies. Our results could indicate the transition of the internal configuration picture that $f_{0} (980)$ looks like a $q q ˉ$ state at high energies although it is described by tetra-quark or $K K ˉ$ molecule state at low energies. It sheds light on a new direction in exotic hadron physics.
Comments:
5 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2511.20217 [pdf]
0 citations
08
[Submitted on 25 Nov 2025] (cross-list from math-ph)
Matrix approximations of operators
B.G. Giraud🇫🇷 · S. Karataglidis🇿🇦 · K. Murulane🇿🇦 · R. Peschanski🇫🇷
The approximate representation of operators by finite matrices is analysed in terms of accuracy and convergence. The identity operator, for example, can be reconstructed using a basis of harmonic oscillator states leading to a narrow peak approximation of the $δ$ function, but this peak may be perturbed by small, residual, oscillations. The peak does not shrink nor grows quickly, and the oscillations only diminish slowly as the size of the matrix increases. For the kinetic energy operator, a triple peak (one positive, two negative) representation of $- δ^{''}$ is obtained, but that is affected also by residual oscillations. Again, convergence is slow as the matrix dimension increases. We find compact formulas to explain such oscillations. Similar observations are found for representations of local interactions, while separable potentials are better represented. As a comparison, in the context of a toy model, the effects of choosing an alternative single particle basis are studied. A formal approach for the approximation of operators is considered for comparison. We conclude with a word of caution for (finite) matrix approximations of operators.
Comments:
30 pages, 25 figures
Subjects:
Mathematical Physics (math-ph); High Energy Physics — Theory (hep-th); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
2511.20381 [pdf]
0 citations
09
[Submitted on 25 Nov 2025] (cross-list from hep-ph)
New framework for extracting GPDs from exclusive photon electroproduction
Jian-Wei Qiu🇺🇸 · Nobuo Sato🇺🇸 · Zhite Yu🇺🇸
Recently, a new framework for studying generic $2 \to 3$ hard exclusive reactions, referred to as single-diffractive hard exclusive processes, has been introduced to provide a cleaner separation of the underlying physical mechanisms. In this work, we expand this formalism to the case of exclusive real-photon electroproduction off a nucleon, $e (ℓ) + N (p) \to e (ℓ^{'}) + N (p^{'}) + γ (q^{'})$ , which represents the classical channel for accessing generalized parton distributions (GPDs) in nucleons and nuclei. This extension enables a more systematic and physically transparent formulation of the reaction dynamics, paving the way for improved extractions of GPDs from experimental data as compared to existing approaches.
Comments:
Match to published version. Main text: 30 pages, 12 figures. Appendix: 17 pages, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2511.20402 [pdf]
PRD(2026)·0 citations
10
[Submitted on 25 Nov 2025] (cross-list from cond-mat.quant-gas)
Precision thermodynamics of the strongly interacting Fermi gas in two dimensions
S. Ramachandran · S. Jensen · Y. Alhassid
The two-species cold atomic Fermi gas with attractive short-range interactions in two spatial dimensions undergoes a Bardeen-Cooper-Schrieffer (BCS) to a Bose-Einstein Condensate (BEC) crossover as a function of $ln (k_{F} a)$ , where $a$ is the scattering length. However, the nature of this crossover in the strong coupling regime $ln (k_{F} a) \sim 1$ remains poorly understood. In this work we use canonical-ensemble auxiliary-field quantum Monte Carlo methods on discrete lattices to calculate several thermodynamical quantities in the strongly interacting regime, and eliminate systematic errors by extrapolating to continuous time and taking the continuum limit. In particular, we present results for the condensate fraction, spin susceptibility, contact, energy equation of state, and the free energy staggering gap. We identify signatures of a pseudogap regime, in which pairing correlations survive above the critical temperature for superfluidity, in the spin susceptibility and in the free energy staggering gap. These results can be used as a benchmark for future experiments.
Comments:
17 pages, 9 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Superconductivity (cond-mat.supr-con); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2511.20599 [pdf]
Eur.Phys.J.ST(2026)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Universal Relations with Dynamical Tides

First determination of fragmentation functions in an exotic-hadron candidate

Matrix approximations of operators

New framework for extracting GPDs from exclusive photon electroproduction

Precision thermodynamics of the strongly interacting Fermi gas in two dimensions

Affiliations