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Nuclear Theory·nucl-th

Wednesday·April 10, 2024

13 papers—5 primary·8 cross-listed

All13Primary5Cross-lists8
  1. 01

    Equation of State of Hot Neutron Star Matter using Finite Range Simple Effective Interaction

    T. R. Routray🇮🇳 · S. Sahoo🇮🇳 · X. Viñas🇪🇸 · D. N. Basu🇮🇳 · M. Centelles🇪🇸

    The equation of state of hot neutron star matter of n+p+e+ composition in -equilibrium is studied for both neutrino-free isothermal and neutrino-trapped isentropic conditions, using the formalism where the thermal evolution is built upon its zero-temperature predictions in a self-consistent manner. The accuracy of the parabolic approximation, often used in the finite temperature calculation of hot neutron star matter, is verified by comparing with the results obtained from the exact evaluation in the neutrino-free neutron star matter. The equation of state of neutrino-trapped isentropic matter at low entropic condition, relevant to the core-collapsing supernovae, is formulated. In the isentropic matter, the particle fractions and equation of state have marginal variance as entropy per particle varies between 1 to 3 (in the unit of k), but the temperature profile shows marked variation. The isentropes are found to be much less sensitive to the nuclear matter incompressibility, but have a large dependence on the slope parameter L. The bulk properties of the neutron stars predicted by the isentropic equation of state for different entropy are calculated. A model calculation for the early stage evolution of the protoneutron star to neutron star configuration is also given.

    nucl-thastro-ph.HEJ.Phys.G(2024)·8 citations
  2. 02

    Shape transition and coexistence in Te isotopes studied with the quadrupole collective Hamiltonian based on a relativistic energy density functional

    K. Suzuki · K. Nomura

    Evolution and coexistence of shape and the related spectroscopic properties of even-even Te isotopes are investigated within the quadrupole collective model that is based on the nuclear density functional theory. By means of the constrained self-consistent mean-field calculations performed within the relativistic Hartree-Bogoliubov method with a choice of the energy density functional and pairing interaction, the deformation-dependent mass parameters and moments of inertia as well as collective potential of the triaxial quadrupole collective Hamiltonian are completely determined. The collective model produces for the near mid-shell nuclei, e.g., Te and Te, the low-energy state, which can be interpreted as the intruder state originating from the strongly deformed prolate minimum in the potential energy surface, along with the ground state that is attributed to the normal state based on a weakly oblate deformed global minimum. The collective model calculation suggests a parabolic behavior of the energy level near the neutron mid-shell , as observed experimentally. Sensitivities of the calculated low-energy spectra to the pairing strength and collective mass parameters are analyzed.

    nucl-thnucl-exPRC(2024)·4 citations
  3. 03

    Variational Optimization for Constructing Inverse Potentials of Proton-Proton Scattering: A Phase Function Method Study

    Lalit Kumar · Arushi Sharma · Anil Khachi · Ayushi Awasthi · O. S. K. S. Sastri

    Background: The phase-shift analysis for proton-proton scattering has been studied by various research groups using the realistic potentials to be comprised of various internal interactions based on an exchange of pions and mesons, involving a large number of parameters. Purpose: The goal of the research is to construct inverse potentials for various l-channels of proton-proton (pp) elastic scattering using the 3-parameter Morse function in combination with atomic Hulthen by utilizing the phase function method and variational optimization technique. Methodology: The implementation of variational optimization begins with randomly assigning initial values to the Morse model parameters. Utilizing the Morse + Hulthen potential as input, the phase equations for various l-channels are numerically solved using the RK-5 method for obtaining the simulated Scattering Phase Shift (SPS). Mean Squared error between simulated and expected SPS has been chosen as the cost function. Variational optimization proceeds iteratively by adjusting potential parameters and re-evaluating the cost function until convergence is achieved. Results: All the obtained scattering phase shifts for various l-channels have been found to converge to a mean squared error <= 0.3. The computed cross-sections matched the experimental ones to less than 1% for energies up to 25 MeV. The scattering parameters are also found to closely match the experimental data. Conclusion: The inverse potentials constructed for various l-channels using Morse + atomic Hulthen are on par with the currently available high-precision realistic potentials.

    nucl-thIndian J.Phys.(2026)·0 citations
  4. 04

    From chiral EFT to perturbative QCD: a Bayesian model mixing approach to symmetric nuclear matter

    A. C. Semposki🇺🇸 · C. Drischler🇺🇸 · R. J. Furnstahl🇺🇸 · J. A. Melendez🇺🇸 · D. R. Phillips🇺🇸

    Constraining the equation of state (EOS) of strongly interacting, dense matter is the focus of intense experimental, observational, and theoretical effort. Chiral effective field theory (EFT) can describe the EOS between the typical densities of nuclei and those in the outer cores of neutron stars while perturbative QCD (pQCD) can be applied to properties of deconfined quark matter, both with quantified theoretical uncertainties. However, describing the full range of densities in between with a single EOS that has well-quantified uncertainties is a challenging problem. Bayesian multi-model inference from EFT and pQCD can help bridge the gap between the two theories. In this work, we introduce a correlated Bayesian model mixing framework that uses a Gaussian Process (GP) to assimilate different information into a single QCD EOS for symmetric nuclear matter. The present implementation uses a stationary GP to infer this mixed EOS solely from the EOSs of EFT and pQCD while accounting for the truncation errors of each theory. The GP is trained on the pressure as a function of number density in the low- and high-density regions where EFT and pQCD are, respectively, valid. We impose priors on the GP kernel hyperparameters to suppress unphysical correlations between these regimes. This, together with the assumption of stationarity, results in smooth EFT-to-pQCD curves for both the pressure and the speed of sound. We show that using uncorrelated mixing requires uncontrolled extrapolation of at least one of EFT or pQCD into regions where the perturbative series breaks down and leads to an acausal EOS. We also discuss extensions of this framework to non-stationary and less differentiable GP kernels, its future application to neutron-star matter, and the incorporation of additional constraints from nuclear theory, experiment, and multi-messenger astronomy.

    nucl-thastro-ph.HEhep-phPRC(2025)·30 citations
  5. 05

    Thermal fluctuations of matter composition and quark nucleation in compact stars

    Mirco Guerrini🇮🇹 · Giuseppe Pagliara🇮🇹 · Alessandro Drago🇮🇹 · Andrea Lavagno🇮🇹

    At the extreme densities reached in the core of neutron stars, it is possible that quark deconfined matter is produced. The formation of this new phase of strongly interacting matter is likely to occur via a first-order phase transition for the typical temperatures reached in astrophysical processes. The first seeds of quark matter would then form through a process of nucleation within the metastable hadronic phase. Here we address the role of the thermal fluctuations in the hadronic composition on the nucleation of two-flavour quark matter. At finite temperature, thermodynamic quantities in a system fluctuate around average values. Being nucleation a local process, it is possible that it occurs in a subsystem whose composition makes the nucleation easier. We will consider the total probability of the nucleation as the product between the probability that a subsystem has a certain hadronic composition different from the average in the bulk, and the nucleation probability in that subsystem. We will show how those fluctuations of the hadronic composition can increase the efficiency of nucleation already for temperatures keV. However, for temperatures MeV, the needed overpressure exceeds the maximum pressure reached in compact stars. Finally, for even larger temperatures the process of nucleation can take place, even taking into account finite size effects.

    nucl-thastro-ph.HEApJ(2024)·5 citations

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first authorsco-authorsvia INSPIRE