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Nuclear Theory·nucl-th

Monday·May 20, 2024

7 papers—5 primary·2 cross-listed

All7Primary5Cross-lists2
  1. 01

    [Submitted on 16 May 2024]

    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 -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 -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 threshold in accordance with the observational data.

    Comments:
    20 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2405.10386 [pdf]
    JCAP(2025)·16 citations
  2. 02

    [Submitted on 17 May 2024]

    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, , 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.

    Comments:
    7 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2405.10503 [pdf]
    PRC(2025)·2 citations
  3. 03

    [Submitted on 17 May 2024]

    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.

    Comments:
    10 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); Data Analysis, Statistics and Probability (physics.data-an); Machine Learning (stat.ML)
    arXiv:
    2405.10839 [pdf]
    PRResearch(2024)·12 citations
  4. 04

    [Submitted on 17 May 2024]

    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.

    Comments:
    12 pages, 0 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Mathematical Physics (math-ph); math.MP (math.MP)
    arXiv:
    2405.10846 [pdf]
    PRD(2025)·4 citations
  5. 05

    [Submitted on 17 May 2024]

    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 particles, Boltzmann's molecular chaos postulate is broken with (almost exact) probability , 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.

    Comments:
    36 pages, 8 figures. v2: published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2405.10878 [pdf]
    PRD(2024)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE