Nuclear Theory·nucl-th

Monday·May 20, 2024

7 papers—5 primary·2 cross-listed

01
Proto-neutron stars with quark cores
Adamu Issifu🇧🇷 · Débora P. Menezes🇧🇷 · Zeinab Rezaei🇮🇷 · Tobias Frederico🇧🇷
This work investigates the evolution of proto-neutron stars (PNSs) from birth as neutrino-rich objects to maturity as cold-catalyzed neutrino-poor objects with nucleonic and non-nucleonic degrees of freedom. The focus is on the star's core where the nucleons, hyperons, and the $Δ$ -isobars are expected to dissolve into a ``soup" of deconfined quarks, at higher baryon densities, to establish a possible hadron-quark phase transition. We separately calculate the nuclear equations of state (EoS) for the hadronic matter (composed of all the baryon octet and $Δ$ -isobars) and the strange quark matter (SQM) under the same thermodynamic conditions characteristic of PNS and proto-strange star (PSS) evolution and construct the hybrid EoS using Maxwell's construction. The study allows us to determine the hadron-quark phase transitions along the evolution lines of the star. We observed a phase transition from hadronic matter to quark matter (QM) phase when the neutrinos have completely escaped from the star's core. The EoSs utilized are constrained to meet the $2 M_{⊙}$ threshold in accordance with the observational data.
nucl-thJCAP(2025)·16 citations
02
Renormalizability of the leading order operator for neutrinoless double beta decay with the effects of finite nucleon size
Tai-Xing Liu🇨🇳 · Ri-Guang Huang🇨🇳 · Dong-Liang Fang🇨🇳
The fundamental process of neutrinoless double beta decay, $nn \to pp e^{-} e^{-}$ , dominated by the exchange of light Majorana neutrinos, is studied in the framework of chiral effective field theory. Considering neutrinos as virtual states, we evaluate the contributions of finite nucleon size to the transition amplitude in a non-perturbative manner, as opposed to expanding these effects in powers of momentum. Based on the nucleon form factors expressed in terms of the dipole and Kelly parametrizations, we find that, at the leading order, the present scheme could renormalize the amplitude in the context of the standard mechanism and provide predictions consistent with the previous investigations. Consequently, we argue that the impact of the effects of finite nucleon size on the amplitude is comparable to that of the leading-order contact term introduced in [Phys. Rev. Lett.120, 202001(2018)] in a perturbative scheme. Our results provide not only a benchmark calculation for the transition amplitude between two schemes but also evidence for the reasonableness of non-perturbative treatment for the effects of finite nucleon size in conventional nuclear many-body methods.
nucl-thhep-phPRC(2025)·2 citations
03
Model orthogonalization and Bayesian forecast mixing via Principal Component Analysis
Pablo Giuliani · Kyle Godbey · Vojtech Kejzlar · Witold Nazarewicz
One can improve predictability in the unknown domain by combining forecasts of imperfect complex computational models using a Bayesian statistical machine learning framework. In many cases, however, the models used in the mixing process are similar. In addition to contaminating the model space, the existence of such similar, or even redundant, models during the multimodeling process can result in misinterpretation of results and deterioration of predictive performance. In this work we describe a method based on the Principal Component Analysis that eliminates model redundancy. We show that by adding model orthogonalization to the proposed Bayesian Model Combination framework, one can arrive at better prediction accuracy and reach excellent uncertainty quantification performance.
nucl-thphysics.data-anstat.MLPRResearch(2024)·12 citations
04
The Convergence Problem Of Gradient Expansion In The Relaxation Time Approximation
Reghukrishnan Gangadharan🇮🇳 · Victor Roy🇮🇳
We obtain a formal integral solution to the 3+1 D Boltzmann Equation in relaxation time approximation. The gradient series obtained from this integral solution contains exponentially decaying non-hydrodynamic terms. It is shown that this gradient expansion can have a finite radius of convergence under certain assumptions of analyticity. We then argue that, in the relaxation time model, proximity to local thermal equilibrium is not necessary for the system to be described by hydrodynamic equations.
nucl-thhep-phhep-thmath-ph+1PRD(2025)·4 citations
05
Modelling stochastic fluctuations in relativistic kinetic theory
Gabriel Soares Rocha · Lorenzo Gavassino · Nicki Mullins
Using the information current, we develop a Lorentz-covariant framework for modeling equilibrium fluctuations in relativistic kinetic theory in the grand-canonical ensemble. The resulting stochastic theory is proven to be causal and covariantly stable, and its predictions do not depend on the choice of spacetime foliation used to define the grand-canonical probabilities. As expected, in a box containing $N > 5$ particles, Boltzmann's molecular chaos postulate is broken with (almost exact) probability $N^{- 1/2}$ , leading to a breakdown of the Boltzmann equation in small systems. We also verify that, in ultrarelativistic gases, transient hydrodynamics already accounts for at least 80% of the equilibrium fluctuations of the stress-energy tensor at a given time. Finally, we compute the correlators at non-equal times for two selected collision kernels: That of a chemically active diluted solution, and that of ultrarelativistic scalar particles self-interacting via a quartic potential. For the former, we compute the density-density correlators analytically in real space, and dehydrodynamization of the stochastic theory is proven to occur whenever the mean free path diverges at high energy.
nucl-thPRD(2024)·17 citations
06
Analytical insights into the interplay of momentum, multiplicity and the speed of sound in heavy-ion collisions
Gabriel Soares Rocha🇺🇸 · Lorenzo Gavassino🇺🇸 · Mayank Singh🇺🇸 · Jean-François Paquet🇺🇸
We introduce a minimal model of ultracentral heavy-ion collisions to study the relation between the speed of sound of the produced plasma and the final particles' energy and multiplicity. We discuss how the particles' multiplicity $N_{tot}$ and average energy $E_{tot} / N_{tot}$ is related to the speed of sound $c_{s}$ by $c_{s}^{2} = d ln (E_{tot} / N_{tot}) / d ln N_{tot}$ if the fluid is inviscid, its speed of sound is constant and all final particles can be measured. We show that finite rapidity cuts on the particles' multiplicity $N$ and energy $E$ introduce corrections between $c_{s}^{2}$ and $d ln (E / N) / d ln N$ that depend on the system's lifetime. We study analytically these deviations with the Gubser hydrodynamic solution, finding that, for ultrarelativistic bosons, they scale as the ratio of the freezeout temperature $T_{FO}$ over the maximum initial temperature of the fluid $T_{0}$ ; the non-thermodynamic aspect of these corrections is highlighted through their dependence on the system's initial conditions.
↳ hep-phnucl-thPRC(2024)·8 citations
07
Solar Models and Astrophysical S-factors Constrained by Helioseismic Results and Updated Neutrino Fluxes
Wuming Yang · Zhijia Tian
The ratio of metal abundance to hydrogen abundance of the solar photosphere, $(Z / X)_{s}$ , has been revised several times. Standard solar models, based on these revised solar abundances, are in disagreement with seismically inferred results. Recently, Magg et al. introduced a new value for $(Z / X)_{s}$ , which is still in debate in the community. The solar abundance problem or solar modeling problem remains a topic of ongoing debate. We constructed rotating solar models in accordance with various abundance scales where the effects of convection overshoot and enhanced diffusion were included. Among these models, those utilizing Magg's abundance scale exhibit superior sound-speed and density profiles compared to models using other abundance scales. Additionally, they reproduce the observed frequency separation ratios $r_{02}$ and $r_{13}$ . These models also match the seismically inferred surface helium abundance and convection zone depth within $1 σ$ level. Furthermore, the calculated neutrino fluxes from these models agree with detected ones at the level of $1 σ$ . We found that neutrino fluxes and density profile are influenced by nuclear reactions, allowing us to use the combination of detected neutrino fluxes and seismically inferred density for diagnosing astrophysical $S$ -factors. This diagnostic approach shows that $S_{11}$ may be underestimated by $2%$ , while $S_{33}$ may be overestimated by about $3%$ in previous determinations. The $S$ -factors favored by updated neutrino fluxes and helioseismic results can lead to significant improvements in solar models.
↳ astro-ph.SRhep-exnucl-thApJ(2024)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Proto-neutron stars with quark cores

Renormalizability of the leading order operator for neutrinoless double beta decay with the effects of finite nucleon size

Model orthogonalization and Bayesian forecast mixing via Principal Component Analysis

The Convergence Problem Of Gradient Expansion In The Relaxation Time Approximation

Modelling stochastic fluctuations in relativistic kinetic theory

Analytical insights into the interplay of momentum, multiplicity and the speed of sound in heavy-ion collisions

Solar Models and Astrophysical S-factors Constrained by Helioseismic Results and Updated Neutrino Fluxes

Affiliations