Nuclear Theory·nucl-th

Thursday·April 9, 2026

10 papers—3 primary·7 cross-listed

01
Relativistic Barnett effect and Curie law in a rigidly rotating free Fermi gas
M. Abedlou Ahadi🇮🇷 · N. Sadooghi🇮🇷
By combining methods from thermal field theory and statistical mechanics, we reexamine the spin polarization caused by the relativistic Barnett effect in a rigidly rotating Fermi gas. We determine the pressure of this medium and show that it depends on an effective chemical potential, which includes contributions from orbital angular momentum-rotation and spin-rotation coupling. We introduce a specific regularization scheme to sum over the angular momentum quantum numbers. As a result, the thermal pressure and all thermodynamic quantities are separated into two parts that differ only in the spin fugacities of spin-up and spin-down fermions. We calculate the Fermi energy for both components and show that the Fermi energy of the spin-down fermions is lower than that of the spin-up ones. This difference arises from the spin-rotation coupling and leads to a spin polarization consistent with the Barnett effect. In particular, we introduce the spin-chemicorotational ratio $η \equiv Ω^{(0)} /2 μ^{(0)}$ , which adjusts the spin polarization of the Fermi gas. Here, $Ω^{(0)}$ and $μ^{(0)}$ represent the angular velocity and chemical potential at zero temperature, respectively. The factor $1/2$ accounts for the fermion's spin. We explore the temperature dependence of $μ$ and $Ω$ , while assuming that the number of spin-up and spin-down fermions remains temperature independent. Our findings indicate that the spin-down component of the rotating Fermi gas dilutes at lower temperatures compared to the spin-up component. Additionally, we calculate the magnetic susceptibility arising from the Barnett magnetization and demonstrate that it is proportional to the moment of inertia $I$ of the rotating Fermi gas. Finally, we prove that $I$ exhibits a $1/ T$ behavior in the high-temperature limit, similar to the Curie law of paramagnetism.
nucl-thcond-mat.quant-gashep-ph0 citations
02
How acausal equations emerge from causal dynamics
Lorenzo Gavassino🇬🇧
We construct a causal and covariantly stable kinetic model whose spectrum at real wavenumbers $k$ reproduces any rest-frame stable dissipative dispersion relation $ω (k)$ via suitable initialization of the microscopic degrees of freedom. Macroscopic observables can therefore obey arbitrary linear evolution equations (including forms that would be acausal if taken as fundamental), while the underlying dynamics remains causal, and all apparent propagation is encoded in the initial data. This provides an explicit counterexample to the idea that microscopic causality alone constrains the analytic form of dispersion relations at real $k$ . In particular, bounds on transport coefficients based solely on the analytic structure of $ω (k)$ , such as the hydrohedron bounds, require additional assumptions about the region in the complex $k$ -plane where $ω (k)$ corresponds to physical modes.
nucl-thhep-thmath-phmath.MP4 citations
03
Nuclear giant resonances from first principles
Sonia Bacca · Francesco Marino · Andrea Porro
This chapter presents an ab initio perspective on giant resonances in atomic nuclei and surveys the principal theoretical frameworks that aim to describe these collective excitations from first principles. While the study of nuclear giant resonances has traditionally been dominated by the energy density functional approach, recent years have witnessed the development of advanced many-body approaches grounded directly in realistic nuclear interactions, namely, Hamiltonians that reproduce nucleon-nucleon phase shifts and accurately describe the binding energies of light nuclei. Within this modern framework, we review the main many-body methods currently used to compute nuclear response functions. These include the random phase approximation, the Lorentz integral transform coupled-cluster theory, the projected generator-coordinate method, and the self-consistent Green's functions approach. After giving a general conceptual and historical overview of giant-resonance phenomena, we outline the theoretical foundations and computational implementations of each method. We conclude with a critical comparison of their predictions for selected benchmark nuclei, $^{16}$ O and $^{40}$ Ca, emphasizing points of agreement and divergence, while maintaining a close connection to the relevant experimental observables.
nucl-th5 citations
04
Anisotropic hybrid stars: Interplay of superconductivity and magnetic field leading to gravitational waves
Zenia Zuraiq🇮🇳 · Banibrata Mukhopadhyay🇮🇳
Neutron stars, at their cores, are highly dense and, thus, are expected to have a number of exotic processes. This includes a possible phase transition to deconfined quark matter at the core, leading to a hybrid star. The quark matter is expected to additionally be color superconducting. The physics of superconductivity plays an important role in understanding the high density matter in the interiors of neutron/hybrid stars. At their high densities, additionally, both proton superconductivity and neutron superfluidity are expected. We study the effect of superconducting (quark/proton) matter, along with the internal magnetic field, leading to pressure anisotropy within hybrid stars. We aim to probe the effect of superconductivity, especially from color superconducting quarks, in hybrid star structure. We propose new phenomenological model anisotropy profiles within a one-dimensional framework. We model quark matter using the vector interaction enhanced Bag model, and hadron matter with the DD2 equation of state. A Maxwell construction joins both phases. We further investigate the possible observational signatures of these hybrid stars. These include mass enhancement and continuous gravitational waves, possibly arising from the anisotropy induced deformation, helping us further constrain our model and its physical parameters.
↳ astro-ph.HEnucl-th1 citation
05
Distribution amplitudes and functions of ground-state scalar and pseudoscalar charmonia
X.-Y. Zeng🇨🇳 · Y.-Y. Xiao🇨🇳 · Z.-N. Xu🇨🇳 · C. D. Roberts🇨🇳 · J. Rodríguez-Quintero🇨🇳
Charmonia are often supposed to provide simple hydrogen-like ``atomic'' systems that can be used to obtain insights into heavier-quark QCD. We use continuum Schwinger function methods to analyse this hypothesis in connection with ground-state scalar and pseudoscalar charmonia and find that a more complex picture of these states may be necessary. For instance, considering orbital angular momentum, the $χ_{c 0}$ is not a simple $P$ -wave system; similarly, the $η_{c}$ wave function contains more than merely $S$ -wave contributions. The distribution amplitudes (DAs) and distribution functions (DFs) of these mesons are also nontrivial. For instance, the $χ_{c 0}$ DA is not positive definite: owing to QCD symmetries, it possesses domains of balanced negative and positive support. This feature is also expressed in the $χ_{c 0}$ DF, but differences between $χ_{c 0}$ and $η_{c}$ DFs diminish under scale evolution. Notably, the light-front momentum fraction carried by glue is the same in both states: it is 10\% less than the in-pion glue momentum fraction. Whilst experimental confirmation of the predictions herein is unlikely, our results should serve as benchmarks for complementary theory attempts to understand local and global structural features of heavier-quark hadrons.
↳ hep-phhep-exhep-latnucl-ex+11 citation
06
Quantum simulation of baryon scattering in SU(2) lattice gauge theory
João Barata🇨🇭 · Juan Hormaza🇨🇴 · Zhong-Bo Kang🇺🇸 · Wenyang Qian🇨🇳
We present a first real-time study of hadronic scattering in a $(1 + 1)$ -dimensional SU(2) lattice gauge theory with fundamental fermions using tensor-network techniques. Working in the gaugeless Hamiltonian formulation, we investigate scattering processes across sectors of fixed global baryon number $B = 0, 1, 2$ , corresponding respectively to meson--meson, meson--baryon, and baryon--baryon collisions. At strong coupling, the $B = 0$ and $B = 2$ channels exhibit predominantly elastic dynamics closely resembling the U(1) Schwinger model. The mixed $B = 1$ sector displays qualitatively new behavior: meson and baryon wavepackets become entangled during the collision, with the slower state becoming spatially delocalized while the faster one propagates ballistically. We characterize these processes through local observables, entanglement entropy, and the information lattice.
↳ hep-lathep-phnucl-thquant-phJ.Subatomic Part.Cosmol.(2026)·0 citations
07
Measurement of inclusive $J / ψ$ polarization in Ru+Ru and Zr+Zr collisions at $s_{NN} = 200$ GeV at STAR
STAR Collaboration
The first measurement of inclusive J/psi polarization at mid-rapidity (|y^{J/psi}| < 0.8) in 200 GeV Ru+Ru and Zr+Zr collisions at sqrt(s_NN) = 200 GeV with the STAR experiment at RHIC is presented. J/psi mesons are reconstructed through their di-electron (e+e-) decay channel. The polarization parameters (lambda_theta, lambda_phi) are measured as a function of the J/psi transverse momentum (p_T) and collision centrality in both the helicity and the Collins-Soper frames. These polarization parameters are found to be consistent with zero across the measured J/psi p_T range of 0.2 < p_T < 10 GeV/c and across collision centralities within 0-80 percent in both frames. These results are consistent with corresponding measurements p+p collisions at the same collision energy and with transport-model calculations.
↳ nucl-exnucl-th0 citations
08
QED radiative corrections in inverse beta decay from virtual pions
Oleksandr Tomalak🇨🇳
Inverse beta decay (IBD), $ν_{e} p \to e^{+} n (γ)$ , is the main detection channel for reactor and supernova antineutrinos. To provide precise IBD cross sections at antineutrino energies $E_{ν_{e}} ≳ 10 MeV$ , we evaluate radiative corrections from virtual pions within the framework of heavy baryon chiral perturbation theory. At leading order, only the pion isospin-breaking contributions are not suppressed by the electron mass. At next-to-leading order, besides recoil effects, only the Wilson coefficient $c_{4}$ contributes to the kinematic dependence. However, its precise value is not relevant for IBD at relatively low energies since all next-to-leading order radiative corrections are relatively small. We find the kinematic dependence of the pion-induced QED radiative corrections at the level and below the uncertainty from the momentum dependence of the nucleon form factors. Our results enable sub-permille theoretical precision of charged-current elastic (anti)neutrino-nucleon scattering at antineutrino energies $E_{ν_{e}} ≳ 10 MeV$ .
↳ hep-phhep-exnucl-exnucl-thJHEP(2026)·2 citations
09
Recent ALICE results from light-ion collision systems
Abhi Modak (on behalf of the ALICE Collaboration)🇮🇹
This article presents recent measurements by the ALICE Collaboration in proton--oxygen (pO), oxygen--oxygen (OO), and neon--neon (Ne--Ne) collisions delivered by the LHC in July 2025. Measurements of the primary charged-particle pseudorapidity density and the elliptic and triangular flow coefficients of charged particles are reported. Experimental evidence of the suppression of neutral pion yields in OO collisions relative to the proton--proton baseline is also discussed. Comparisons of these new data with theoretical models provide key input to understand particle production, collective phenomena, and parton energy loss in small collision systems.
↳ nucl-exhep-exnucl-th2 citations
10
Light mesons in the symmetric-vertex approximation
M.N. Ferreira🇧🇷 · A.S. Miramontes🇪🇸 · J.M. Morgado🇪🇸 · J. Papavassiliou🇪🇸
We compute the spectrum of light mesons, composed by up, down, and strange quarks, using a symmetry-preserving approximation that permits the inclusion of fully-dressed quark-gluon vertices in the key dynamical equations. This method is characterized by the use of the standard symmetric kinematic configuration as a seed in the corresponding Schwinger-Dyson equation, yielding finally the full kinematic dependence of all eight form factors composing the transversely-projected quark-gluon vertex. The extension of this approach to the case of distinct nonvanishing current quark masses is discussed, and the compatibility with the fundamental Ward-Takahashi identities demonstrated. The corresponding Bethe-Salpeter kernel is composed by three different diagrammatic structures, which may be deduced from the attendant quark gap equation by applying the standard "cutting" rules. The masses of the light mesons are computed by first determining the eigenvalue of the Bethe-Salpeter equation as a function of Euclidean momenta, and then using the Schlessinger extrapolation method to determine the Minkowski momentum for which this eigenvalue becomes unity. The resulting meson masses are in good agreement with experimental values, and substantially improve upon predictions from the rainbow-ladder approximation.
↳ hep-phhep-latnucl-thEPJC(2026)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE