Nuclear Theory·nucl-th

Friday·August 14, 2026

8 papers—3 primary·5 cross-listed

01
Relativistic dynamical effects in proton emission: the Wentzel-Kramers-Brillouin method for 1+1 dimensional Dirac equation
Guangping Chen · Wenmin Deng · Ganlong Ding · Sibo Wang · Jing Peng · Haozhao Liang
Starting from the $1 + 1$ dimensional (one spatial and one temporal dimension) Dirac equation, we employ the Wentzel-Kramers-Brillouin (WKB) approximation to derive the corresponding relativistic penetration probability. The derivation shows that the semiclassical momentum is determined by the Schrödinger-equivalent potential $U_{eff} (r) = S (r) + \frac{E}{m} V (r) + \frac{S ^{2} ( r ) - V ^{2} ( r )}{2 m}$ , instead of the simple sum of scalar and vector potentials $S (r) + V (r)$ , which has been adopted widely in the studies of relativistic quantum tunneling. We then quantify the relativistic dynamical effects in proton emission by comparing the results obtained with $U_{eff} (r)$ and those obtained with $S (r) + V (r)$ . Incorporating $U_{eff} (r)$ systematically reduces the penetration probability and the assault frequency, and consequently increases the predicted half-life. The relativistic dynamical effect becomes more pronounced with higher orbital angular momentum and can reach about $84%$ in the half-life of $^{144} Tm$ .
nucl-thnucl-ex0 citations
02
Parametric Matrix Models for Emulation in Nuclear and Many-Body Physics
Patrick Cook
Progress in nuclear and many-body physics today is predicated on the ability to solve large-scale, strongly correlated quantum many-body problems. As the theoretical models become more sophisticated, they also become more computationally complex. Simultaneously, quantifying uncertainty in model predictions and fitting free parameters to experimental observations requires repeated evaluation of these expensive models. Surrogate models---known as emulators---provide the means of accomplishing these goals. This thesis provides an introduction into the current state of emulation in nuclear and many-body physics. The motivations, goals, and origins of currently popular emulation methods are discussed along with selected examples. We see how many methods are closely mathematically related and how trade-offs are made to optimize specific properties or applications. The central work in this thesis is the method of parametric matrix models (PMMs), an emulation and general machine learning framework which combines aspects of traditional reduced basis method with modern parametric machine learning. PMMs are able to retain as much or as little physical information about the underlying system as desired, yielding not only excellent performance but also nearly unparalleled adaptability, interpretability, and trustworthiness as an emulation method. A formal mathematical framework for PMMs is developed and accompanied by practical step-by-step procedures for the application of the method. As part of this thesis, the open-source pyPMM package was developed. This package enables any researcher to construct, train, share, and deploy PMM-based emulators with modular, extendable, and graphics processing unit (GPU)-optimized code. All PMM examples in this thesis were created using this package.
nucl-thphysics.comp-ph0 citations
03
Effective field theory of quasi-hydrodynamics from kinetic theory
Lorenzo Gavassino🇬🇧
Quasi-hydrodynamics describes systems with quasi-conserved degrees of freedom, namely observables that relax on timescales that are finite but parametrically longer than microscopic relaxation times. Examples include kinetic chemistry and linear viscoelasticity. Here, we develop a rigorous effective-field-theory framework for linear quasi-hydrodynamics from kinetic-type theories. Starting from any linearized, causal kinetic-like theory endowed with slow degrees of freedom, we show that the exact dynamics of conserved and quasi-conserved observables admits a systematic expansion in the fast relaxation timescale. At zeroth order, the resulting equations form a causal, symmetric-hyperbolic theory belonging to the appropriate transient-hydrodynamic universality class, establishing Israel-Stewart-like dynamics as the universal description of slow relaxation modes. Higher-order corrections can be computed systematically and inherit universal symmetry, Onsager, positivity, and causality constraints from the underlying microscopic theory.
nucl-thhep-thmath-phmath.MP0 citations
04
How Neutron Star Radii Encode the Dense-Matter Equation of State and Hadron-Quark Transition
Bao-An Li🇺🇸 · Xavier Grundler🇺🇸
We investigate how future high-precision neutron star (NS) radius measurements encode microscopic information about the dense-matter equation of state (EOS), focusing on a possible first-order hadron--quark phase transition and the resulting mass--radius topology. Within a Bayesian framework using meta-model EOSs with nine microscopic parameters, we analyze mock radius measurements $R_{1.4} = 11.9 \pm σ_{R}$ km with $σ_{R} = 0.9$ and $0.1$ km for canonical NSs. We introduce inverse EOS--radius mappings that give the posterior mean of each EOS parameter as a function of $R_{1.4}$ . Their slope measures radius sensitivity, while their curvature determines the leading precision dependence of the posterior mean through the Jensen expansion. Resolving the mappings into four mass--radius topologies, Connected, Disconnected, Both, and No-Quark-Matter, reveals a clear hierarchy of information. The symmetry-energy parameters $L$ (slope) and $K_{sym}$ (curvature) are strongly encoded in $R_{1.4}$ and their posterior means shift appreciably with improved radius precision, whereas the higher-order hadronic parameters show stronger topology dependence. Among the transition parameters, the transition density $ρ_{t}$ is the most strongly encoded in $R_{1.4}$ , while the energy-density jump and quark-matter sound speed are more strongly associated with the topology of the full mass--radius sequence. Since the different topologies have strongly overlapping $R_{1.4}$ distributions, even precise radius measurements cannot by themselves identify the topology or uniquely determine the high-density transition properties. These results provide a parameter-dependent hierarchy for assessing the scientific return of future high-precision radius measurements and complementary probes of high-density
↳ astro-ph.HEhep-phnucl-exnucl-th1 citation
05
Massive cold hybrid stars in a modified Polyakov-Nambu-Jona-Lasinio model
Sk Md Adil Imam · Pedro Costa · Mariana Dutra · Odilon Lourenço · Renan Pereira · Constança Providência
We propose a modified Polyakov-loop Nambu--Jona-Lasinio (mPNJL) model in which the Polyakov potential is given by an explicit dependence on the quark chemical potential, allowing it to remain finite at zero temperature and thus to describe the confinement-deconfinement transition in cold dense matter. Combining this modified quark sector with hadronic equations of state via a Maxwell construction, we find that, depending on the model parameters, the equation of state can exhibit either two phase transitions, from hadronic matter to confined (quarkyonic) quark matter and subsequently to deconfined quark matter, or a single transition directly from hadronic to deconfined quark matter or from hadronic to quarkyonic quark matter. Stable massive cold hybrid stars with only quarkyonic and/or deconfined quark phase are obtained. We systematically examine how the parameters of the modified Polyakov potential and the quark vector interactions control the location of these transitions, and find that repulsive vector interactions are essential to obtain a stable quark core. Hybrid stars with quarkyonic and/or a deconfined core can reach maximum masses above $2 M_{⊙}$ , provided a sufficiently stiff hadronic equation of state is used at low density. In the core of the maximum-mass configurations, the speed of sound exceeds the conformal limit, $c_{s}^{2} = 1/3$ , for the quarkyonic core stars. This work establishes the qualitative role of each model parameter in shaping hybrid-star structure.
↳ hep-phastro-ph.HEgr-qcnucl-th0 citations
06
Magnetization and Magnetic Field-Induced Correction: Implications for QGP Thermal Photon Production in Magnetohydrodynamic
Jing Jing🇨🇳 · Duan She🇨🇳 · Ze-Fang Jiang🇨🇳
We investigate thermal photon emission from magnetized quark-gluon plasma (QGP) within (1+1)-dimensional relativistic magnetohydrodynamics (MHD), systematically incorporating magnetic susceptibility $χ_{m}$ ---encompassing both constant and lattice-QCD-derived temperature-dependent $χ_{m} (T)$ parametrizations---and weak-field quantum corrections to quark distribution functions $f_{EM}$ . Employing the Pu-Bjorken MHD framework, we calculate photon production rates from Compton scattering, $q q ˉ$ annihilation, bremsstrahlung, and annihilation with rescattering, and integrate these over the QGP spacetime evolution to obtain transverse momentum ( $p_{T}$ ) spectra. Our results demonstrate that photon yields are predominantly governed by the initial magnetic field strength and its temporal decay profile, with $χ_{m}$ exerting negligible influence in the explored parameter space. In contrast, the weak-field correction $f_{EM}$ induces a distinct enhancement in thermal photon production at intermediate $p_{T}$ . This work establishes a rigorous theoretical framework for quantifying electromagnetic observables in magnetized QGP and provides the foundation for future dissipative MHD studies incorporating spin-magnetization dynamics.
↳ hep-phnucl-th0 citations
07
Non-perturbative quark production and transport in the evolving glasma: the WAGASHI event generator
Nicholas J. Benoit🇹🇼 · Chiho Nonaka🇯🇵 · Hidetoshi Taya🇯🇵
We study non-perturbative quark-antiquark pair production and the subsequent quark dynamics in the earliest glasma stage of relativistic heavy-ion collisions. For that, we develop a new model, WAGASHI (Wong-precessing Anisotropic Glasma And ScHwinger-produced Initial-conditions), which combines classical Yang-Mills glasma evolution, Wong-equation transport, and Schwinger pair production on an event-by-event basis. We find that a sizeable number of quarks, comparable to the final hadron yields, are produced already during the glasma stage and subsequently undergo substantial momentum broadening and spin randomization, suggesting a significant contribution toward the early equilibration of the quark-gluon plasma. We also determine the event-by-event distributions of baryon number, electric charge, strangeness, and spin polarization in Pb-Pb and O-O collisions at LHC energies, finding particularly large fluctuations in the smaller O-O system. These results provide dynamical initial conditions for the subsequent hydrodynamic evolution of the quark-gluon plasma.
↳ hep-phhep-exnucl-exnucl-th0 citations
08
The Production of Electron-Capture Elements in Thermonuclear Supernovae: Theory vs. Observations
S. Shiber · P. Hoeflich · T. Mera · E. Fereidouni · Z. Levy · D. Maci · C. Ashall · K. Medler · J. M. DerKacy · E. Baron · M. Shahbandeh · C. M. Pfeffer
Type Ia supernovae (SNe Ia) explosively destroy carbon-oxygen white dwarfs (WDs) in multiple stellar systems. They produce approximately 50% of the iron-group elements in the Universe, synthesize electron-capture (EC) elements, drive nuclear physics experiments, and underpin high-precision cosmology. To first order, the outcome is governed by nuclear physics, a property often described as stellar amnesia. Recently, this stellar amnesia has begun to be broken by the nearly universal detection of EC elements with JWST. These elements trace high-density burning, largely ruling out the currently popular helium-triggered, sub-Mch detonation models as the dominant channel. Instead, the ubiquitous presence of EC is shifting back the focus to dynamical and secular mergers, and near-Mch explosions similar to the deflagration model W7, but in which the nuclear flame undergoes a deflagration-to-detonation transition. The early deflagration phase is especially important because spherical simulations identify the central WD density, and thus the WD mass, as a key parameter governing the explosion. Here, we present detailed magneto-hydrodynamical simulations. We find that small-scale, pre-existing turbulence expected from the pre-explosion smoldering phase is essential for overcoming the fundamental challenges imposed by the intrinsic 3D physics. This turbulence systematically reduces the production of EC elements by about a factor of two, implying the need for WD central densities closer to those associated with accretion-induced collapse to a neutron star. We also demonstrate the effect of magnetic fields near the saturation field strength and highlight the need for higher-precision EC rates at low Ye.
↳ astro-ph.SRastro-ph.HEnucl-thphysics.plasm-ph0 citations

Affiliations

first authorsco-authorsvia INSPIRE