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Nuclear Theory·nucl-th

Friday·October 3, 2025

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 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
  2. 02

    Gamow shell model description of exceptional point in 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 Li, an EP is found for the 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 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
  3. 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 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
  4. 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 Li from the \textit{p}-shell, F from the \textit{sd}-shell, and two heavier nuclei (Po, and Pb). We run circuits representing their ground states on a noisy simulator (IBM's \textit{FakeFez} backend) and quantum hardware (). For heavier nuclei, we demonstrate the feasibility of simulating Po and 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

Affiliations

first authorsco-authorsvia INSPIRE