Nuclear Theory·nucl-th

Friday·October 3, 2025

10 papers—4 primary·6 cross-listed

01
Nonlinear causality and strong hyperbolicity of baryon-rich Israel-Stewart hydrodynamics
Ian Cordeiro🇺🇸 · Fábio S. Bemfica🇺🇸 · Enrico Speranza🇮🇹 · Jorge Noronha🇺🇸
We present the first set of fully-nonlinear, necessary and sufficient conditions guaranteeing causal evolution of the initial data for the Israel-Stewart hydrodynamic equations with shear and bulk viscosity coupled to a nonzero baryon current. These constraints not only provide nonlinear causality: they also (a) guarantee the existence of a locally well-posed evolution of the initial data (they enforce strong hyperbolicity) when excluding the endpoints of the bounds, (b) arise from purely algebraic constraints that make no underlying symmetry assumptions on the degrees of freedom and (c) propagate the relevant symmetries of the degrees of freedom over the entire evolution of the problem. Our work enforces a mathematically rigorous foundation for future studies of viscous relativistic hydrodynamics with baryon-rich matter including neutron star mergers and heavy-ion collisions.
nucl-thastro-ph.HEgr-qcEPJ Web Conf.(2026)·2 citations
02
Gamow shell model description of exceptional point in $^{7}$ Li
David Cardona Ochoa🇫🇷 · Marek Płoszajczak🇫🇷 · Nicolas Michel🇨🇳
We report the first identification of an exceptional point (EP) within the Gamow Shell Model in the Coupled Channels representation (GSM-CC). In the spectrum of $^{7}$ Li, an EP is found for the $5/ 2^{-}$ doublet, where the two states coalesce in both energy and width, the phase rigidity vanishes, and the S-matrix develops a double pole. These features manifest directly in observables: the elastic cross section acquires a split-peak structure, and the phase shift shows a single $2 π$ jump. This work demonstrates that GSM-CC provides a powerful framework to explore EP phenomena in nuclei and their experimental signatures.
nucl-thEPJ Web Conf.(2025)·2 citations
03
The sharpness of the quark-hadron transition and the properties of hybrid stars
M. B. Albino🇵🇹 · R. Fariello🇧🇷 · G. Lugones🇧🇷 · F. S. Navarra🇧🇷
We investigate the effects of the sharpness of the phase transition between hadronic matter and quark matter on various properties of neutron stars. We construct hybrid equations of state by combining a hadronic model with a quark model using a Gaussian function. This approach introduces a smooth transition characterized by two parameters: one representing the overpressure relative to the first-order phase transition point, and the other related to the range over which the hybrid region extends in baryon chemical potential. We find that the sharpness of the phase transition significantly influences the equation of state, which can deviate by several tens of $MeV fm^{- 3}$ from the one with a sharp first-order transition. The speed of sound exhibits diverse behaviors, including drastic drops, pronounced peaks, and oscillatory patterns, depending on the sharpness parameters. In terms of stellar structure, while the maximum neutron star mass remains largely unaffected by the sharpness of the phase transition, the stellar radii can vary significantly. Smoother transitions lead to a leftward shift (up to 1 km) of the mass-radius curve segment corresponding to hybrid stars. The tidal deformability decreases with smoother transitions, especially for higher-mass stars. Our results are quite general and do not qualitatively depend on the specific hadronic and quark matter models employed. In fact, the hybrid equation of state and stellar properties derived from microscopic models of quark-hadron pasta phases display the same behavior as described above.
nucl-thInt.J.Mod.Phys.D(2025)·1 citation
04
A low-circuit-depth quantum computing approach to the nuclear shell model
Chandan Sarma🇬🇧 · Paul Stevenson🇬🇧
In this work, we introduce a new qubit mapping strategy for the Variational Quantum Eigensolver (VQE) applied to nuclear shell model calculations, where each Slater determinant (SD) is mapped to a qubit, rather than assigning qubits to individual single-particle states. While this approach may increase the total number of qubits required in some cases, it enables the construction of simpler quantum circuits that are more compatible with current noisy intermediate-scale quantum (NISQ) devices. We apply this method to seven nuclei: Four lithium isotopes $^{6 - 9}$ Li from the \textit{p}-shell, $^{18}$ F from the \textit{sd}-shell, and two heavier nuclei ( $^{210}$ Po, and $^{210}$ Pb). We run circuits representing their ground states on a noisy simulator (IBM's \textit{FakeFez} backend) and quantum hardware ( $ibm_p i tt s b u r g h$ ). For heavier nuclei, we demonstrate the feasibility of simulating $^{210}$ Po and $^{210}$ Pb as 22- and 29-qubit systems, respectively. Additionally, we employ Zero-Noise Extrapolation (ZNE) via two-qubit gate folding to mitigate errors in both simulated and hardware-executed results. Post-mitigation, the best results show less than 4 \% deviation from shell model predictions across all nuclei studied. This SD-based qubit mapping proves particularly effective for lighter nuclei and two-nucleon systems, offering a promising route for near-term quantum simulations in nuclear physics.
nucl-thDiscover Quant.Sci.(2026)·9 citations
05
Hadron resonance gas is not a good model for hadronic matter in a strong magnetic field
Pasi Huovinen🇵🇱 · Michał Marczenko🇵🇱 · Michał Szymański🇵🇱 · Bithika Karmakar🇵🇱 · Pok Man Lo🇵🇱 · Chihiro Sasaki🇵🇱 · Krzysztof Redlich🇵🇱
We study the effect of magnetic field on particle yields and charge fluctuations in hadron resonance gas. We argue that the big changes in the proton yield and baryon number susceptibility are due to ill-defined description of higher-spin states, and that because of detailed balance, neutral resonances must be affected by the field too.
↳ hep-phnucl-thEPJ Web Conf.(2026)·2 citations
06
Singly heavy tetraquark resonant states with multiple strange quarks
Xin-He Zheng🇨🇳 · Yao Ma🇨🇳 · Shi-Lin Zhu🇨🇳
We systematically investigate the S-wave singly heavy tetraquark systems containing two or three strange quarks, $Q s s ˉ s ˉ$ , $Q n s ˉ s ˉ$ and $Q s s ˉ n ˉ (Q = c, b, n = u, d)$ , within the constituent quark potential model. We solve the four-body Schrödinger equation using the Gaussian expansion method (GEM) and identify resonances via the complex scaling method (CSM). There are no bound states below the lowest two-meson thresholds. We obtain several compact resonances with $J^{P} = 0^{+}, 2^{+}$ in $Q s s ˉ s ˉ$ , and $J^{P} = 2^{+}$ in $Q n s ˉ s ˉ$ and $Q s s ˉ n ˉ$ . The pole positions are mainly distributed around $7.0 - 7.2$ GeV (bottom) and $3.7 - 3.9$ GeV (charm), with widths from a few to several tens of MeV. These resonances decay into $D_{s} η^{'}, D_{(s)}^{*} ϕ, D_{s}^{*} K^{*}$ and $D_{s}^{*} K ˉ^{*}$ (and their bottom counterparts), providing targets for future experimental searches.
↳ hep-phhep-exhep-latnucl-thPRD(2026)·5 citations
07
Particle momentum spectra, correlations, and maximum entropy principle in high-multiplicity collision events
S.V. Akkelin🇺🇦
In this paper, we utilize the maximum entropy prescription to determine a quantum state of a small collision system at the kinetic freeze-out. We derive expressions for multiplicity-selected particle momentum spectra and correlation functions by applying a fixed particle number constraint to this state. The results of our analysis can be useful for interpreting the multiplicity dependence of the particle momentum spectra and correlations in high-multiplicity $pp$ collision events at a fixed LHC energy.
↳ hep-phhep-thnucl-thPRD(2025)·0 citations
08
Dispersion relations: foundations
Bastian Kubis🇩🇪
We give a pedagogical introduction to the founding ideas of dispersion relations in particle physics. Starting from elementary mechanical systems, we show how the physical principle of causality is closely related to the mathematical property of analyticity, and how both are implemented in quantum mechanical scattering theory. We present a personal selection of elementary applications such as the relation between hadronic production amplitudes or form factors to scattering, and the extraction of resonance properties on unphysical Riemann sheets. More advanced topics such as Roy equations for pion--pion scattering and dispersion relations for three-body decays are briefly touched upon.
↳ hep-phnucl-th5 citations
09
Light S-wave pentaquarks on the light front
Fangcheng He🇺🇸 · Edward Shuryak🇺🇸 · Wan Wu🇺🇸 · Ismail Zahed🇺🇸
We construct an explicit basis set for pentaquark states on a regular 4-simplex, that diagonalizes the Hamiltonian for light pentaquarks with confinement on the light front (LF). The ensuing eigenstates are free of the center of mass motion and satisfy exact Dirichlet boundary conditions. Hyperfine interactions in the form of color-spin or flavor-spin are shown to lift the degeneracy of the 16 pentastates, with a spectrum that compares fairly with some of the empirical nucleon excited states. The quark PDF for the light pentastates is discussed.
↳ hep-phnucl-thPRD(2026)·3 citations
10
Parton distributions in the shockwave formalism
Shohini Bhattacharya🇺🇸 · Chuan-Qi He🇺🇸 · Zhong-Bo Kang🇺🇸 · Diego Padilla🇺🇸 · Jani Penttala🇺🇸
In this work, we calculate a broad class of parton distributions - including parton distribution functions (PDFs), transverse-momentum-dependent distributions (TMDs), generalized parton distributions (GPDs), generalized transverse-momentum-dependent distributions (GTMDs), and diffractive parton distributions - directly from their operator-level definition in the shockwave approximation for the target nucleon. This approximation is valid in the high-energy limit of scattering, corresponding to the small- $x$ regime. The shockwave framework allows us to employ the eikonal approximation and express the parton distributions in terms of Wilson-line correlators, naturally formulated within the color-glass condensate effective field theory. We present a comprehensive set of Feynman rules for evaluating parton distributions in this limit, and demonstrate how they can be systematically applied to calculate all phenomenologically relevant leading-twist parton distributions at leading order. This work establishes a unified starting point for future studies that aim to bridge the color-glass condensate approach with the partonic description of the nucleon.
↳ hep-phnucl-thJHEP(2026)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE