Nuclear Theory·nucl-th

Tuesday·August 26, 2025

16 papers—11 primary·5 cross-listed

12
$r$ -process Heating Feedback on Disk Outflows from Neutron Star Mergers
Li-Ting Ma · Kuo-Chuan Pan · Meng-Ru Wu · Rodrigo Fernández
Neutron star mergers produce $r$ -process elements, with yields that are sensitive to the kinematic and thermodynamic properties of the ejecta. These ejecta properties are potentially affected by dynamically-important feedback from $r$ -process heating, which is usually not coupled to the hydrodynamics in post-merger simulations modeling the ejecta launching and expansion. The multi-messenger detection of GW170817 showed the importance of producing reliable ejecta predictions, to maximize the diagnostic potential of future events. In this paper, we develop a prescription for including $r$ -process heating as a source term in the hydrodynamic equations. This prescription depends on local fluid properties and on the $Y_{e}$ history as recorded by dedicated tracer particles, which exchange information with the grid using the Cloud-in-Cell method. The method is implemented in long-term viscous hydrodynamic simulations of accretion disk outflows to investigate its feedback on ejecta properties. We find that $r$ -process heating can increase the unbound disk ejecta mass by $\sim 10%$ relative to a baseline case that only considers alpha particle recombination. Nuclear heating also enhances the radial velocity of the ejecta with $Y_{e} < 0.25$ by up to a factor of two, while concurrently suppressing marginally-bound convective ejecta.
↳ astro-ph.HEnucl-thApJ(2026)·3 citations
13
A Journey of Seeking Pressure and Forces in the Nucleon
Xiangdong Ji🇺🇸 · Chen Yang🇺🇸
Momentum current density (MCD) $T^{ij}$ is a general physics concept describing the momentum conservation through momentum flow generated from both the kinetic motion of particles and the interacting forces among them. It has been suggested by M. Polyakov et al. that the MCD in the nucleon, characterized by the form factor $C / D$ of the QCD energy-momentum tensor, can be interpreted as the pressure and shear forces between adjacent parts of the system because the nucleon interior approximates a continuous medium. While intuitively appealing, we find that the interpretation is hard to justify from a detailed examination of the physical mechanisms for the momentum flow in QCD. After reviewing through a broad range of classical and quantum systems, we find that while thermal and/or quantum average of isotropic motion contributes to kinetic MCD a pressure term proportional to $δ^{ij}$ , when there is an anisotropic motion, the pressure cannot simply be identified from the MCD tensor. Furthermore, kinetic pressure cannot be considered as the surface force between adjacent parts of a system. More importantly, at the scale of the nucleon dimension, the color forces among quarks and gluons is by no means short-ranged as in a continuous medium, and the resulting interaction MCD cannot be interpreted as normal or shear ``stress'' force, although an isotropic term from the QCD trace anomaly may be interpreted as a ``vacuum pressure.'' Following our previous study of force densities through divergences of kinetic MCDs, we affirm that the vacuum pressure term provides a confining potential on the quarks through color Lorentz forces.
↳ hep-phhep-latnucl-thNPB(2026)·30 citations
14
Baryon Electric Charge Correlation as QCD Magnetometer
Heng-Tong Ding🇨🇳 · Jin-Biao Gu🇨🇳 · Arpith Kumar🇨🇳 · Sheng-Tai Li🇨🇳
The detection of strong magnetic fields in peripheral heavy-ion collisions is crucial for observing effects such as the chiral magnetic effect but has proven exceptionally difficult. To address this, we propose the baryon electric charge correlation $χ_{11}^{BQ}$ and the chemical potential ratio $μ_{Q} / μ_{B}$ as sensitive probes of magnetic fields, based on (2+1)-flavor lattice QCD simulations at the physical pion mass. Along the transition line, $χ_{11}^{BQ}$ and $(μ_{Q} / μ_{B})_{LO}$ in Pb-Pb collisions increase by factors of 2.1 and 2.4 at $e B ≃ 8 M_{π}^{2}$ , respectively. To bridge theoretical predictions with experimental observables, we implement systematic kinematic cuts that emulate detector acceptances of the STAR and ALICE experiments within the hadron resonance gas model. This allows us to construct experimentally relevant proxy observables. Furthermore, we demonstrate that $(μ_{Q} / μ_{B})_{LO}$ is also sensitive to the collision system, showing a $1.5$ -fold increase from Zr-Zr to Ru-Ru isobar collisions. Our findings offer new insights into thermo-magnetic effects and provide experimentally relevant guidance for the detection of magnetic fields in heavy-ion collisions.
↳ hep-lathep-phnucl-exnucl-thEPJ Web Conf.(2026)·2 citations
15
Spontaneous breaking of global U(1) symmetry in an interacting Bose gas under rigid rotation
E. Siri🇮🇷 · N. Sadooghi🇮🇷
We investigate the impact of rigid rotation on the spontaneous breaking of U(1) symmetry in a Bose gas, which is described by a self-interacting complex scalar field Lagrangian. Rigid rotation is introduced through a specific metric that explicitly depends on the angular velocity $Ω$ . We begin by determining the free propagator for this model at finite temperature $T$ and chemical potential $μ$ . Using this propagator, we calculate the thermodynamic potential in terms of an energy dispersion relation $ϵ_{k}$ . It is found that in both the U(1) symmetric phase and the symmetry-broken phase, two energy branches emerge. In the symmetry-broken phase, they are identified with a massive phonon and a massless roton mode. Notably, rotation does not alter $ϵ_{k}$ at low momentum. Setting $μ = 0$ , we use the total thermodynamic potential, which includes classical, thermal, vacuum, and nonperturbative ring contributions, to explore how the condensate depends on $T$ and $Ω$ . We first focus on the classical and thermal parts of the thermodynamic potential and find that the critical temperature of the U(1) phase transition scales as $Ω^{1/3}$ . By identifying the (pseudo-)Goldstone and non-Goldstone modes of this model with $π$ and $σ$ mesons, we calculate the $T$ and $Ω$ dependence of masses $m_{π}$ and $m_{σ}$ . We demonstrate that the Goldstone theorem holds only when the one-loop (thermal) corrections to $m_{σ}$ and $m_{π}$ are taken into account. We further explore the $T$ and $Ω$ dependence of the condensate, determine the $σ$ dissociation temperatures for fixed $Ω$ , and compare them with the critical temperature of the phase transition. Additionally, we emphasize the role played by the nonperturbative ring potential, especially in altering the order of the phase transition with and without rotation.
↳ hep-phcond-mat.quant-gashep-thnucl-th4 citations
16
Sensitivity of neutrinoless double beta decays from a combined analysis of ground and excited states
C. R. Ding🇨🇳 · K. Han🇨🇳 · S.B. Wang🇨🇳 · J. M. Yao🇨🇳
Next-generation neutrinoless double-beta ( $0 ν β β$ ) decay experiments, with projected half-life sensitivities approaching $1 0^{28}$ years, aim to probe the entire parameter space of the inverted neutrino mass ordering in the light-neutrino-exchange scenario. However, this reach remains uncertain by the substantial model dependence of the nuclear matrix elements (NMEs). In this work, we propose a strategy based on a combined analysis of $0 ν β β$ decays to both the ground state and the first excited $0^{+}$ state of the daughter nucleus. We show that such a multi-channel approach can significantly enhance experimental sensitivity, depending on the underlying NME predictions. This method is particularly well-suited for large liquid xenon detectors, such as the proposed PandaX-xT and XLZD experiments, which can efficiently identify transitions of $^{136}$ Xe to excited states. Our results highlight the importance of exploiting multiple decay channels in future $0 ν β β$ searches to maximize their discovery potential.
↳ hep-phhep-exnucl-exnucl-thPLB(2026)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

r-process Heating Feedback on Disk Outflows from Neutron Star Mergers

A Journey of Seeking Pressure and Forces in the Nucleon

Baryon Electric Charge Correlation as QCD Magnetometer

Spontaneous breaking of global U(1) symmetry in an interacting Bose gas under rigid rotation

Sensitivity of neutrinoless double beta decays from a combined analysis of ground and excited states

Affiliations

$r$ -process Heating Feedback on Disk Outflows from Neutron Star Mergers