Nuclear Theory·nucl-th

Friday·January 24, 2025

11 papers—1 primary·10 cross-listed

01
[Submitted on 21 Jan 2025]
Strongly Interacting Matter Under Extreme Conditions
Somenath Pal🇮🇳
Different variants of the Hadron Resonance Gas model have been used to describe the hadronic phase of strongly interacting matter. HRG model is improved by including repulsive interaction through the inclusion of excluded volume in Excluded Volume Hadron Resonance Gas (EVHRG) model. Here, the EVHRG model is further improved by incorporating unequal radii of hadrons which has been named as Modified Excluded Volume Hadron Resonance Gas (MEVHRG) model and also by taking their Lorentz contraction in Lorentz contracted MEVHRG model, namely, LMEVHRG model. Another way of incorporating the repulsive interactions in the HRG model is through the introduction of a mean-field potential. This is done in the HRG mean-field (HRGMF) model where the single particle energies are modified by a density dependent term. Both the inclusion of unequal radii and the Lorentz contraction have significant effects on the thermodynamic quantities and susceptibilities of conserved charges. The centre of mass energy dependence of some thermodynamic quantities in presence of repulsive interaction has been studied. Our study clearly indicates that proper modelling of repulsive interaction among hadrons is very important to explain the thermodynamic quantities and susceptibilities of conserved charges. The effect of static magnetic field in HRG and EVHRG models by the means of Landau levels has also been investigated. The vacuum part of the pressure, in presence of magnetic field, has been properly renormalised. The magnetic field is found to effect the thermodynamic quantities and the susceptibilities significantly. The electric charge susceptibility is influenced more strongly by the magnetic field than the baryon susceptibility. The total magnetization of hadronic matter is found to be positive.
Comments:
PhD Thesis, 124 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2501.13123 [pdf]
1 citation
02
[Submitted on 20 Jan 2025] (cross-list from hep-lat)
QCD Equation of State with $N_{f} = 3$ Flavors up to the Electroweak Scale
Matteo Bresciani (Milan Bicocca U. and INFN, Milan Bicocca)🇮🇹 · Mattia Dalla Brida (Milan Bicocca U. and INFN, Milan Bicocca)🇮🇹 · Leonardo Giusti (Milan Bicocca U. and INFN, Milan Bicocca)🇮🇹 · Michele Pepe (INFN, Milan Bicocca)🇮🇹
The equation of state of Quantum Chromodynamics with $N_{f} = 3$ flavors is determined non-perturbatively in the range of temperatures between $3$ and $165$ ~GeV with a precision of about $0.5$ - $1.0$ \%. The calculation is carried out by numerical simulations of lattice gauge theory discretized à la Wilson with shifted boundary conditions in the compact direction. At each given temperature the entropy density is computed at several lattice spacings in order to extrapolate the results to the continuum limit. Taken at face value, data point straight to the Stefan-Boltzmann value by following a linear behavior in the strong coupling constant squared. They are also compatible with the known perturbative formula supplemented by higher order terms in the coupling constant, a parametrization which describes well our data together with those present in the literature down to $500$ MeV.
Comments:
9 pages, 6 plots, version published in Phys. Rev. Lett
Subjects:
High Energy Physics — Lattice (hep-lat); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2501.11603 [pdf]
PRL(2025)·23 citations
03
[Submitted on 21 Jan 2025] (cross-list from gr-qc)
Extending Israel-Stewart theory: Causal bulk viscosity at large gradients
Lorenzo Gavassino🇺🇸
We present a class of relativistic fluid models for cold and dense matter with bulk viscosity, whose equilibrium equation of state is polytropic. These models reduce to Israel-Stewart theory for small values of the viscous stress $Π$ . However, when $Π$ becomes comparable to the equilibrium pressure $P$ , the evolution equations "adjust" to prevent the onset of far-from-equilibrium pathologies that would otherwise plague Israel-Stewart. Specifically, the equations of motion remain symmetric hyperbolic and causal at all times along any continuously differentiable flow, and across the whole thermodynamic state space. This means that, no matter how fast the fluid expands or contracts, the hydrodynamic equations are always well-behaved (away from singularities). The second law of thermodynamics is enforced exactly. Near equilibrium, these models can accommodate an arbitrarily complicated dependence of the bulk viscosity coefficient $ζ$ on both density and temperature.
Comments:
14 pages, 7 figure, published on PRD (see https://journals.aps.org/prd/abstract/10.1103/PhysRevD.111.083014)
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2501.12543 [pdf]
PRD(2025)·1 citation
04
[Submitted on 22 Jan 2025] (cross-list from hep-lat)
Symmetry of screening masses of mesons in two-flavor lattice QCD at high temperatures
Yasumichi Aoki🇯🇵 · Hidenori Fukaya🇯🇵 · Shoji Hashimoto🇯🇵 · Issaku Kanamori🇯🇵 · Yoshifumi Nakamura🇯🇵 · Christian Rohrhofer🇯🇵 · Kei Suzuki🇯🇵 · David Ward🇯🇵
We investigate spatial two-point correlation functions of mesonic operators in two-flavor lattice QCD at high temperatures. The simulated temperatures over the range $T \in [147, 330]$ MeV, where the critical temperature is estimated around 165 MeV. To ensure a good control of the chiral symmetry we employ the Möbius domain-wall fermion action for two degenerate flavors of quarks. With a lattice cut off $a^{- 1} \sim 2.6$ GeV, the residual mass is reduced to 0.14 MeV. With the energy spectrum obtained from the screening mass at incremental values of the temperature range, we examine the $S U (2)_{L} \times S U (2)_{R}$ chiral symmetry, the anomalous axial $U (1)$ as well as an enhanced symmetry which exchanges the spin degrees of freedom. We also study how the data approaches the perturbative prediction given by twice the Matsubara frequency of free quarks.
Comments:
27 pages + 2 page appendix, 13 figures, v2 added author name to arXiv metadata, v3 added citations, additional footnotes, and reorganized appendix plots, v4 added DOI, additional plots and revisions from review
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2501.12675 [pdf]
PRD(2025)·8 citations
05
[Submitted on 22 Jan 2025] (cross-list from hep-lat)
Non-relativistic QCD Study of Excited Bottomonia at Finite Temperatures on a Fine Lattice
Heng-Tong Ding🇨🇳 · Wei-Ping Huang🇨🇳 · Rasmus Larsen🇩🇪 · Stefan Meinel🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸
The temperature dependence of bottomonium correlators up to the 3S and 3P excited states are presented in the range $T ≃ 133 - 250$ MeV. These lattice calculations employ the non-relativistic QCD (NRQCD) approach for bottom quarks on (2+1)-flavor gauge backgrounds, using the highly improved staggered quark (HISQ) action near the physical point. The study utilizes a fine lattice spacing of 0.0493 fm at all temperatures. Extended bottomonium operators are implemented to achieve optimized overlaps with the targeted excited states, enhancing sensitivity to thermal effects. To probe in-medium modifications of excited bottomonia, we extract thermal widths and in-medium masses from bottomonium correlators, parameterizing the spectral function with a Gaussian ansatz. Our results confirm nonzero thermal widths for various bottomonium states as the temperature increases, while no significant mass shifts are observed. Additionally, we check that the in-medium properties of bottomonia are almost not affected by variations in the choice of extended operators.
Comments:
11 pages, 4 figures, talk presented at the 41st International Symposium on Lattice Field Theory (Lattice2024), July 28th - August 3rd, 2024, Liverpool, UK
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2501.12777 [pdf]
PoS(2025)·0 citations
06
[Submitted on 22 Jan 2025] (cross-list from hep-ph)
Simultaneous description of high density QCD matter in heavy ion collisions and neutron star observations
Jan Steinheimer🇩🇪 · Manjunath Omana Kuttan🇩🇪 · Tom Reichert🇩🇪 · Yasushi Nara🇯🇵 · Marcus Bleicher🇩🇪
A combined constraint on the QCD equation of state, at high densities, from connecting neutron star observations to data from heavy ion reactions is presented. We use the Chiral Mean Field Model which can describe neutron star and iso-spin symmetric matter and allows the consistent calculation of the density and momentum dependent potentials of baryons which are then implemented in the UrQMD transport model. In contrast to previous studies, the same equation of state constrained from neutron star properties is also able to describe experimental observables in heavy ion reactions at the HADES experiment. Unlike many other approaches our results are not constraint to densities up to nuclear saturation or perturbative results which allows a continuous description of the equation of state over a large range in baryon density.
Comments:
9 pages 7 figures and 1 table
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2501.12849 [pdf]
PLB(2025)·22 citations
07
[Submitted on 22 Jan 2025] (cross-list from astro-ph.HE)
The impact of hyperons on neutron star mergers: gravitational waves, mass ejection and black hole formation
Hristijan Kochankovski🇪🇸 · Georgios Lioutas🇩🇪 · Sebastian Blacker🇩🇪 · Andreas Bauswein🇩🇪 · Angels Ramos🇪🇸 · Laura Tolos🇪🇸
We study the influence of hyperons in binary neutron star (NS) mergers considering a total of 14 temperature dependent equations of state (EoSs) models which include hyperonic degrees of freedom and partly delta resonances. Thermally produced hyperons induce a higher heat capacity and a lower thermal index, i.e. a reduced thermal pressure for a given amount of thermal energy, compared to purely nucleonic models. We run a large set of relativistic hydrodynamics simulations of NS mergers to explore the impact on observables of these events. In symmetric binaries, we describe a characteristic increase of the dominant postmerger gravitational-wave (GW) frequency by a few per cent, which is specifically linked to the occurrence of hyperons and can thus be potentially used as a discriminator between purely nucleonic and hyperonic systems. We corroborate that this effect occurs similarly for asymmetric binaries and becomes more prominent with increasing total binary mass. Hyperonic models tend to stick out in relations between the dominant postmerger GW frequency and the tidal deformability of massive stars providing a signature to identify the presence of hyperons. Distinct secondary postmerger GW spectral features are differently affected by the presence of hyperons, in the sense that one feature exhibits a characteristic frequency shift due to the specific thermal properties of hyperonic EoSs while the other does not. The dynamical mass ejection of mergers is tentatively enhanced for hyperonic models in comparison to nucleonic EoSs which yield roughly the same stellar properties of cold NSs. This may serve useful to identify exotic degrees of freedom in these systems by kilonova observations. Also, for hyperonic EoSs the threshold mass for prompt black hole formation is reduced by about 0.05 $M_{⊙}$ in comparison to nucleonic systems with the same stellar parameters of cold NSs.
Comments:
31 pages, 28 figures, accepted for publication in PRD
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2501.12905 [pdf]
PRD(2025)·19 citations
08
[Submitted on 7 Jan 2025] (cross-list from hep-ph)
The Open Relativistic Two-body Problem
A.V.Koshelkin🇷🇺
The open relativistic two-body problem, when two interacting particles also are in external potentials, is considered in terms of the principle of the least action. Based on the consistent modification of the relativistic version Newton's third law in external fields, the exact covariant operator equations, which govern dynamics of either a scalar particle or each of the components of the 16 component spinor of spin- $1/2$ fermions, depending on the particle type, are derived in the center-mass and relative motion variables, beyond the consideration in the Breit frame only. The class of external fields and interaction potentials, when the two-body problem can be covariantly reformulated in (3+1) phase space of relative motion variables, uncoupled from the center-mass motion of such a system, is outlined. In the case of fermions the new $γ$ -matrix basis generating the Dirac-like equation for the 16 component spinors in the (3+1) phase space is found. The chosen basis allows us to decouple the derived Dirac-like equation into four independent equations governing the dynamics of the four-component spinors. The developed approach is examined in studying the low-energy positronium states in magnetic fields.
Comments:
24 pages. 0 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2501.13110 [pdf]
Int.J.Theor.Phys.(2025)·1 citation
09
[Submitted on 22 Jan 2025] (cross-list from astro-ph.HE)
Comparison of Three Methods for Triggering Core-collapse Supernova Explosions in Spherical Symmetry
Liliya Imasheva (1,2) · H.-Thomas Janka (1) · Achim Weiss (1,2) ((1) MPI Astrophysics, Garching, (2) LMU Munich)
Despite the three-dimensional nature of core-collapse supernovae (CCSNe), simulations in spherical symmetry (1D) play an important role to study large model sets for the progenitor-remnant connection, explosion properties, remnant masses, and CCSN nucleosynthesis. To trigger explosions in 1D, various numerical recipes have been applied, mostly with gross simplifications of the complex microphysics governing stellar core collapse, the formation of the compact remnant, and the mechanism of the explosion. Here we investigate the two most popular treatments, piston-driven and thermal-bomb explosions, in comparison to 1D explosions powered by a parametric neutrino engine in the P-HOTB code. For this comparison we calculate CCSNe for eight stars and evolution times up to 10,000 s, targeting the same progenitor-specific explosion energies as obtained by the neutrino-engine results. Otherwise we employ widely-used ("classic") modelling assumptions, and alternatively to the standard contraction-expansion trajectory for pistons, we also test suitably selected Lagrangian mass shells adopted from the neutrino-driven explosions as "special trajectories." Although the 56Ni production agrees within roughly a factor of two between the different explosion triggers, neither piston nor thermal bombs can reproduce the correlation of 56Ni yields and explosion energies found in neutrino-driven explosions. This shortcoming as well as the problem of massive fallback witnessed in classical piston models, which diminishes or extinguishes the ejected nickel, can be largely cured by the special trajectories. These and the choice of the explosion energies, however, make the modelling dependent on pre-existing neutrino-driven explosion results.
Comments:
21 pages, 13 figures, 7 tables; including minor revisions due to referee comments; accepted by MNRAS
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2501.13172 [pdf]
MNRAS(2025)·15 citations
10
[Submitted on 22 Jan 2025] (cross-list from hep-ph)
Distribution Functions of a Radially Excited Pion
Z.-N. Xu🇪🇸 · Z.-Q. Yao🇪🇸 · D. Binosi🇮🇹 · M. Ding🇨🇳 · C. D. Roberts🇨🇳 · J. Rodríguez-Quintero🇪🇸
A nonperturbatively-improved, symmetry-preserving approximation to the quantum field equations relevant in calculations of meson masses and interactions is used to deliver predictions for all distribution functions (DFs) of the ground state pion, $π_{0}$ , and its first radial excitation, $π_{1}$ , viz. valence, glue, and sea. Regarding Mellin moments of the valence DFs, the $m = 0, 1$ moments in both states are identical; but for each $m \geq 2$ , that in the $π_{0}$ is greater than its partner in the $π_{1}$ . Working with such information, pointwise reconstructions of the hadron-scale $π_{0, 1}$ valence DFs are developed. The predicted $π_{0}$ valence DF is consistent with extant results. The $π_{1}$ valence DF is novel: it possesses three-peaks, with the central maximum partnered by secondary peaks on either side, each separated from the centre by a zero: the zeroes lie at $x \approx 0.2, 0.8$ and the secondary peaks at $x \approx 0.1, 0.9$ . Evolution to $ζ = 3.2$ GeV, a typical scale for nonperturbative calculations, is accomplished using an evolution scheme for parton DFs that is all-orders exact. At this higher scale, differences between the $π_{0, 1}$ valence DFs remain significant, but analogous differences between glue and sea DFs are far smaller. This analysis shows that, owing to constraints imposed by chiral symmetry and the pattern by which it is broken in Nature, there are noticeable differences between the structural properties of the pion ground state and its radial excitations.
Comments:
11 pages, 5 figures, 4 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2501.13243 [pdf]
EPJC(2025)·7 citations
11
[Submitted on 23 Jan 2025] (cross-list from hep-lat)
Towards a parameter-free analysis of the QCD chiral phase transition and its universal critical behavior
Sabarnya Mitra🇩🇪 · Frithjof Karsch🇩🇪
To quantify the universal properties of chiral phase transition in (2+1)-flavor QCD, we use an improved, renormalized order parameter for the chiral symmetry breaking. We construct ratios of this divergence-free order parameter from its values for different pairs of light quark masses. From this, we determine in a parameter-independent manner, the chiral phase transition temperature $T_{c}$ and the associated critical exponent $δ$ of the universality class. We present first numerical results of these calculations on $N_{τ} = 8$ lattices, with staggered fermions.
Comments:
4 pages, 2 figures, Contribution to the proceedings of 26th DAE BRNS High Energy Physics symposium 2024
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2501.13653 [pdf]
Springer Proc.Phys.(2026)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE