Nuclear Theory·nucl-th

Tuesday·December 23, 2025

18 papers—9 primary·9 cross-listed

10
[Submitted on 19 Dec 2025] (cross-list from physics.flu-dyn)
Achieving angular-momentum conservation with physics-informed neural networks in computational relativistic spin hydrodynamics
Hidefumi Matsuda🇨🇳 · Koichi Hattori🇨🇳 · Koichi Murase🇯🇵
We propose physics-informed neural networks (PINNs) as a numerical solver for relativistic spin hydrodynamics and demonstrate that the total angular momentum, i.e., the sum of orbital and spin angular momentum, is accurately conserved throughout the fluid evolution by imposing the conservation law directly in the loss function as a training target. This enables controlled numerical studies of the mutual conversion between spin and orbital angular momentum, a central feature of relativistic spin hydrodynamics driven by the rotational viscous effect. We present two physical scenarios with a rotating fluid confined in a cylindrical container: one case in which initial orbital angular momentum is converted into spin angular momentum in analogy with the Barnett effect, and the opposite case in which initial spin angular momentum is converted into orbital angular momentum in analogy with the Einstein-de Haas effect. We investigate these conversion processes governed by the rotational viscous effect by analyzing the spacetime profiles of thermal vorticity and spin potential. Our PINNs-based framework provides the first numerical evidence for spin-orbit angular momentum conversion with fully nonlinear computational relativistic spin hydrodynamics.
Comments:
24pages, 16figures
Subjects:
Fluid Dynamics (physics.flu-dyn); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
2512.17971 [pdf]
3 citations
11
[Submitted on 19 Dec 2025] (cross-list from astro-ph.HE)
Constrained Gaussian-process bridge prior for neutron-star equation-of-state inference
Tyler Gorda🇺🇸 · Oleg Komoltsev🇩🇪 · Aleksi Kurkela🇳🇴 · Eirik Sunde🇳🇴
We set forth a new method for generating model-agnostic, nonparametric priors for neutron star equation-of-state inference that are stable, causal and thermodynamically consistent by construction. This generalizes Gaussian processes to include global thermodynamic constraints, specifically allowing the inclusion of any number of training points in the form $(μ, n, p)$ while retaining thermodynamic consistency between them. The method is based on constructing constrained Gaussian-process bridges, whose correlation properties can be tuned at will allowing flexibility between a conservative prior and a theory-informed prior. The method does not require any shooting to obey multiple constraints and provides an efficient and informed way to include both chiral effective field theory and perturbative quantum chromodynamics constraints within the same framework.
Comments:
Version 2: the published version. 17 pages, 9 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2512.18044 [pdf]
ApJ(2026)·11 citations
12
[Submitted on 19 Dec 2025] (cross-list from hep-ph)
Quantum simulation of real-time current correlators and DIS-inspired observables in the Schwinger model
Kazuki Ikeda🇺🇸 · Zhong-Bo Kang🇺🇸 · Dmitri E. Kharzeev🇺🇸 · Wenyang Qian🇪🇸
Hadronic tensors encode the nonperturbative structure of hadrons probed in deep inelastic scattering (DIS), yet their direct evaluation requires real-time evolution that presents a challenge for traditional Euclidean lattice approaches. In this work, we present the first quantum simulation of real-time hadronic current-current correlators in a confining gauge theory, from which DIS-inspired structure functions are extracted as a proof-of-principle demonstration in the Schwinger model, i.e (1+1)-dimensional QED. Using two complementary quantum-simulation strategies -- quantum-circuit and tensor-network methods -- we compute the real-time current-current correlator directly on the lattice and validate our results against exact diagonalization where applicable. From this correlator, we compute the hadronic tensor and determine the longitudinal structure function, the sole nonvanishing DIS observable in two space-time dimensions. Our study demonstrates that quantum simulation offers a viable complementary pathway towards the evaluation of real-time observables relevant for hadronic structure. It also provides a foundation for extending the calculations from Schwinger model to other gauge theories.
Comments:
22 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2512.18062 [pdf]
JHEP(2026)·4 citations
13
[Submitted on 21 Dec 2025] (cross-list from hep-ph)
Collapse of Coulomb Bound States of Vector Bosons
V.V. Flambaum🇦🇺 · H. B. Tran Tan🇺🇸
Charged spin 1 (vector) particles behave very differently from electrons or scalars in a Coulomb field. For an infinitely heavy point-like nucleus their bound state wave functions fall to the centre, and embedding the system in a renormalisable electroweak-type theory does not remedy this short-distance pathology. We therefore solve the pure Coulomb problem for a finite nuclear radius $R$ and recover the point nucleus limit by letting $R \to 0$ . This approach allows us to include the crucial Upsilon term in the wave equations, which for the point-like nucleus is proportional to delta(r) and was ignored in the previous calculations of the energy spectrum. Several unusual effects emerge: (i) The Upsilon term supports a tower of states located mainly inside the nucleus. As R -> 0 their number diverges, most lying in the negative energy continuum (energy epsilon < - m c^2). They trigger vacuum breakdown - particle-antiparticle pair creation that ultimately screens the nuclear charge. (ii) Ordinary Sommerfeld-like states (with binding energy smaller m c^2) persist, but a finite fraction of each wave function leaks into the nucleus, even as R -> 0. (iii) Charge density of a negatively charged vector particle changes sign in a vicinity of the nucleus and becomes positive charge density, whereas the Upsilon term ensures its density inside the nucleus remains negative. (iv) For weak coupling, Z alpha << 1, yet with mR <Z alpha, the non-relativistic solution differs qualitatively from Schrodinger theory despite binding energies are well below m c^2; agreement is recovered only when Z alpha << mR. These phenomena highlight the distinctive and subtle behaviour of spin-1 particles in the Coulomb field.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2512.18691 [pdf]
PRD(2026)·0 citations
14
[Submitted on 21 Dec 2025] (cross-list from hep-ph)
Emergent chiral spin symmetry, non-perturbative dynamics and thermoparticles in hot QCD
Owe Philipsen🇩🇪
Several non-perturbative results for hot QCD are challenging some aspects of the phase diagram and its associated degrees of freedom which were previously believed to be well understood. With increasing temperature, the chiral crossover is followed by an intermediate region with an approximate chiral spin symmetry larger than chiral symmetry, in which pseudo-scalar mesons continue to exist as hadron-like excitations, before at some higher temperature the expected chiral symmetry is recovered. By testing general formal considerations against lattice data, it can be shown that thermally modified versions of stable vacuum particles, so-called thermoparticles, form the constituents of thermal quantum field theories, with properties quite different from what is expected perturbatively. This ``viewpoint'' aims to raise broader and, in particular, phenomenological interest in these directions.
Comments:
Invited EPJA viewpoint, 9 pages, 5 figures; typos corrected, reference added, matches published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2512.18830 [pdf]
EPJA(2026)·1 citation
15
[Submitted on 22 Dec 2025] (cross-list from hep-ph)
Hydrodynamic Short-Range Correlations from Boltzmann-Langevin Equation
Li Yan🇨🇳 · Derek Teaney🇺🇸
We investigate hydrodynamic contributions to short-range two-particle correlations in relativistic heavy-ion collisions using the Boltzmann-Langevin equation. We derive and solve the transport equation for equal-time two-point correlations, obtaining both local and non-local contributions that scale with transport coefficients. The non-local correlations emerging from 2-to-2 scattering dynamics provide a hydrodynamic signature in short-range correlation measurements.
Comments:
Contribution to Proceedings of Quark Matter 2025
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2512.19039 [pdf]
EPJ Web Conf.(2026)·0 citations
16
[Submitted on 22 Dec 2025] (cross-list from nucl-ex)
Measurement of Fifth- and Sixth-Order Fluctuations of (Net-)proton Number in Au+Au Collisions from Phase II of the Beam Energy Scan Program at RHIC
The STAR Collaboration
We report high-statistics measurements of fifth- and sixth-order factorial cumulants and cumulant ratios of (net-)proton multiplicity distributions in Au+Au collisions at $s_{N N} = 7.7$ --27 GeV, using data from the STAR experiment collected during the Beam Energy Scan Phase~II at RHIC. Protons and antiprotons are identified at midrapidity ( $∣ y ∣ < 0.5$ ) with transverse momentum $0.4 < p_{T} < 2.0$ GeV/ $c$ . The proton factorial cumulants $κ_{4}$ , $κ_{5}$ , and $κ_{6}$ increase with order but exhibit no sign alternation within current uncertainties, offering no evidence for a two-component structure in the proton multiplicity distribution, as might be expected near a first-order phase transition. The cumulant ratios $C_{5} / C_{1}$ and $C_{6} / C_{2}$ fluctuate around zero in collisions at 0--40\% centrality. The results are consistent with both the negative predictions from lattice QCD (LQCD) and the positive trends obtained from the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. At $s_{N N} ≳ 27$ GeV, the $C_{4} / C_{2}$ and $C_{5} / C_{1}$ results are compatible with predictions from lattice QCD, functional renormalization group (FRG), and hadron resonance gas (HRG) models, while UrQMD describes the data better at lower energies. These measurements place constraints on baryon number fluctuations and offer valuable insights into the QCD phase structure.
Comments:
8 pages and 5 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2512.19352 [pdf]
PRC(2026)·2 citations
17
[Submitted on 22 Dec 2025] (cross-list from astro-ph.HE)
Strong model-agnostic constraints for twin-star solutions
Sofia Blomqvist🇫🇮 · Christian Ecker🇩🇪 · Tyler Gorda🇺🇸 · Aleksi Vuorinen🇫🇮
We perform a model-agnostic Bayesian analysis of the neutron-star-matter equation of state (EoS), using known ab-initio constraints and astrophysical observations to limit its behavior at intermediate densities. Permitting explicit first-order phase transitions allows us to systematically search for twin-star solutions, i.e. the existence of stars degenerate in mass but differing in radius. We find that current observational constraints exclude all but two classes of twin stars. The first is characterized by a first-order transition occurring at a very low density, where the material properties of the system either stay largely intact or move away from the conformal limit. In the second, more interesting class, the discontinuity in the mass-radius curve emerges after a rapid crossover transition at a significantly higher density, with the speed of sound exhibiting two sharp peaks at distinct densities. Since neither class shows clear conformalization upon entering the second branch, the standard twin-star scenario linking the mass-radius discontinuity to deconfinement can be firmly ruled out, while even the remaining solutions -- disfavored by per-mille Bayes factors and in tension with theoretical bounds -- are likely to be excluded in the future.
Comments:
9 pages, 3 figures, 2 appendices
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2512.19477 [pdf]
PRD(2026)·9 citations
18
[Submitted on 22 Dec 2025] (cross-list from quant-ph)
Trigonometric continuous-variable gates and hybrid quantum simulations of the sine-Gordon model
Tommaso Rainaldi🇺🇸 · Victor Ale🇺🇸 · Matt Grau🇺🇸 · Dmitri Kharzeev🇺🇸 · Enrique Rico🇨🇭 · Felix Ringer🇺🇸 · Pubasha Shome🇺🇸 · George Siopsis🇺🇸
Hybrid qubit-qumode quantum computing platforms provide a natural setting for simulating interacting bosonic quantum field theories. However, existing continuous-variable gate constructions rely predominantly on polynomial functions of canonical quadratures. In this work, we introduce a complementary universality paradigm based on trigonometric continuous-variable gates, which enable a Fourier-like representation of bosonic operators and are particularly well suited for periodic and non-perturbative interactions. We present a deterministic ancilla-based method for implementing unitary and non-unitary trigonometric gates whose arguments are arbitrary Hermitian functions of qumode quadratures. As a concrete application, we develop a hybrid qubit-qumode quantum simulation of the lattice sine-Gordon model. Using these gates, we prepare ground states via quantum imaginary-time evolution, simulate real-time dynamics, compute time-dependent vertex two-point correlation functions, and extract quantum kink profiles under topological boundary conditions. Our results demonstrate that trigonometric continuous-variable gates provide a physically natural framework for simulating interacting field theories on near-term hybrid quantum hardware, while establishing a parallel route to universality beyond polynomial gate constructions. We expect that the trigonometric gates introduced here to find broader applications, including quantum simulations of condensed matter systems, quantum chemistry, and biological models.
Comments:
26 pages, 8 figures
Subjects:
Quantum Physics (quant-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2512.19582 [pdf]
JHEP(2026)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE