Nuclear Theory·nucl-th

Wednesday·June 3, 2026

16 papers—10 primary·6 cross-listed

11
Hybrid stars among mass gap objects are excluded by twin stars at $1.4 M_{⊙}$
Alexander Ayriyan🇵🇱 · David Blaschke🇵🇱 · Marcin Dubaj🇵🇱 · Oleksandr Vitiuk🇵🇱 · Adrian Wojcik
We investigate the question whether compact objects in the so called mass gap ( $2.5 < M / M_{⊙} < 5.0$ ) can be neutron stars or hybrid stars. Using a generic hybrid star equation of state with a first-order deconfinement transition, we map the allowed parameter space in a Seidov-type diagram and confront it with modern mass--radius constraints. We find that mass-gap hybrid stars require an extremely early onset of deconfinement and very stiff quark matter. The Bayesian analysis, however, favors equations of state with deconfinement at typical neutron-star masses around $1.4 M_{⊙}$ with mass-twin stars that, if confirmed, would rule out hybrid stars as candidates for observed mass-gap compact objects.
↳ astro-ph.HEhep-phnucl-th0 citations
12
Stochastic Dynamics of Heavy Quarks in Strongly Coupled Plasma
Krishna Rajagopal🇺🇸 · Bruno Scheihing-Hitschfeld🇺🇸 · Urs Achim Wiedemann🇨🇭
We study the stochastic dynamics of heavy quarks propagating through the strongly coupled plasma of $N = 4$ supersymmetric Yang-Mills (SYM) theory at nonzero temperature in terms of the corresponding Kolmogorov equation, which correctly describes their kinetic equilibration and the non-Gaussian fluctuations in their momenta without having to restrict their velocity to the non-relativistic regime. Leveraging the heavy quark limit, we show that the evolution of the momentum space distribution function can be reformulated as a Hamilton-Jacobi problem, and therefore can be solved in terms of first-order ordinary differential equations. We solve these evolution equations in an infinite thermal plasma with a constant temperature for initial conditions specified by spherically symmetric heavy quark momentum distributions with a phenomenologically motivated shape that is steeply falling at large momentum. To highlight the distinctive features of the kinetic equilibration process, we compare their solutions with Fokker-Planck dynamics with the same drag coefficient and fluctuations chosen by hand to guarantee equilibration. We find qualitatively similar dynamics at small momentum, and very different dynamics at large momentum, where, much like in jet quenching phenomena, the steepness of the momentum distribution gives a larger relevance to unlikely events in which a heavy quark loses little momentum in a given time step. Such events are much less unlikely in the Kolmogorov evolution than in Fokker-Planck evolution with the same mean energy loss, meaning that equilibration at large momentum is significantly delayed. Our results provide a systematic description of heavy quarks propagating through strongly coupled plasma from the ultra-relativistic to the non-relativistic regime and point the way towards implementation in phenomenological studies.
↳ hep-phhep-thnucl-th4 citations
13
Projected Energy Correlators: Two-Loop Jet Functions and NNLL Resummation
Kyle Lee🇺🇸 · Yibei Li🇩🇪 · Zhen Xu🇩🇪 · Xiaoyuan Zhang🇺🇸
We present the next-to-next-to-leading logarithmic (NNLL) collinear resummation of projected $N$ -point energy correlators (ENCs) up to $N = 6$ , matched to fixed-order predictions at NLO, in both electron-positron annihilation and Higgs decay to gluons. The key new ingredient is the two-loop jet function for $N = 4, 5, 6$ , which we compute semi-analytically using Integration-by-Parts and differential equations. We further include the leading non-perturbative corrections for ENCs, described by two universal soft matrix elements $Ω_{1 q}, Ω_{1 g}$ of order $Λ_{QCD}$ , whose evolution is governed by anomalous dimensions for $(N - 1)$ -point correlators. The matched distributions are compared with parton-shower simulations from Pythia8 and Herwig7, and we study the sensitivity of both the absolute spectra and their ratios to the two-point energy correlator under variations of $α_{s}$ and $Ω_{1 q, 1 g}$ . Our results show that higher-point projected energy correlators are now under quantitative control at NNLL accuracy, opening the door to future $α_{s}$ extractions with complementary systematics.
↳ hep-phhep-exnucl-th5 citations
14
Magnetized bottom-up thermalization in heavy-ion collisions
Ritesh Ghosh🇹🇼 · Igor A. Shovkovy🇺🇸
We investigate how a strong magnetic field generated in noncentral heavy-ion collisions may modify the bottom-up equilibration scenario. In the conventional weak-coupling picture, the earliest stages of the evolution are dominated by overoccupied gluons, while quark production is parametrically delayed. In a background magnetic field, however, additional inelastic channels become kinematically allowed or enhanced, most notably gluon decay into quark-antiquark pairs, $g \to q + q ˉ$ . Using parametric estimates, we show that for sufficiently strong fields, with $∣ e B ∣$ approaching the saturation scale squared, $Q_{s}^{2}$ , magnetic-field-induced quark production can become important during the earliest stages of bottom-up evolution. This mechanism can populate the hard quark sector, modify the chemical composition of the pre-equilibrium matter, and provide an additional pathway toward chemical equilibration. We also discuss possible back-reaction effects, including quark-antiquark annihilation, depletion of the hard-gluon sector, and the potential feedback of early quark production on the electromagnetic conductivity of the medium. This exploratory study of a magnetically assisted bottom-up scenario provides a natural extension of the standard framework, with qualitative predictions that depend sensitively on the lifetime and spacetime profile of the magnetic field.
↳ hep-phnucl-th0 citations
15
Chiral Quark Soliton Model And Nucleon Parton Distribution Functions
Masashi Wakamatsu🇯🇵
The chiral quark soliton model (CQSM) is an effective quark model of baryons maximally taking account of the most important feature of low-energy QCD, i.e., the spontaneous chiral symmetry breaking of the QCD vacuum and the associated appearance of Nambu--Goldstone pions. It shares many common features with the famous Skyrme model in that the baryons are viewed as rotating hedgehog objects in both models. Despite many similarities, it turned out that the CQSM can give more realistic predictions on most baryon observables. Above all, a decisive advantage of the CQSM over the Skyrme-like models is that it can handle non-local quark--quark correlations in baryons, which is absolutely impossible within the framework of effective meson theories. This feature is decisively important for making theoretical predictions on the quark distribution functions inside the nucleon, which are defined as nucleon matrix elements of bilinear quark operators with light-cone separation. In the present paper, we try to elucidate why and how the CQSM can give successful predictions for a variety of types of nucleon quark distribution functions, especially for the flavor asymmetry of the unpolarized and longitudinally polarized sea-quark (anti-quark) distribution functions in the nucleon.
↳ hep-phhep-exnucl-thSymmetry(2026)·0 citations
16
Phase structure of strong interaction matter from Functional QCD
Christian S. Fischer🇩🇪 · Jan M. Pawlowski🇩🇪
In this contribution to the Encyclopedia of Nuclear Physics, we aim to provide a pedagogical introduction to the functional approach to QCD at finite temperature and chemical potential. We briefly outline the general framework and address its complementarity to other first-principle approaches to non-perturbative QCD. We discuss selected results obtained with Dyson-Schwinger equations (DSE) and the functional renormalisation group (fRG) in the context of a general physics perspective on the QCD phase diagram. This article is specifically aimed at students and non-practitioners of functional methods alike and may serve as a short guide to further literature.
↳ hep-phhep-exhep-latnucl-th5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Hybrid stars among mass gap objects are excluded by twin stars at 1.4M⊙​

Stochastic Dynamics of Heavy Quarks in Strongly Coupled Plasma

Projected Energy Correlators: Two-Loop Jet Functions and NNLL Resummation

Magnetized bottom-up thermalization in heavy-ion collisions

Chiral Quark Soliton Model And Nucleon Parton Distribution Functions

Phase structure of strong interaction matter from Functional QCD

Affiliations

Hybrid stars among mass gap objects are excluded by twin stars at $1.4 M_{⊙}$