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Nuclear Theory·nucl-th

Monday·May 8, 2023

8 papers—3 primary·5 cross-listed

All8Primary3Cross-lists5
  1. 01

    Nonparametric model for the equations of state of neutron star from deep neural network

    Wenjie Zhou · Jinniu Hu · Ying Zhang · Hong Shen

    It is of great interest to understand the equation of state (EOS) of the neutron star (NS), whose core includes highly dense matter. However, there are large uncertainties in the theoretical predictions for the EOS of NS. It is useful to develop a new framework, which is flexible enough to consider the systematic error in theoretical predictions and to use them as a best guess at the same time. We employ a deep neural network to perform a non-parametric fit of the EOS of NS using currently available data. In this framework, the Gaussian process is applied to represent the EOSs and the training set data required to close physical solutions. Our model is constructed under the assumption that the true EOS of NS is a perturbation of the relativistic mean-field model prediction. We fit the EOSs of NS using two different example datasets, which can satisfy the latest constraints from the massive neutron stars, NICER, and the gravitational wave of the binary neutron stars. Given our assumptions, we find that a maximum neutron star mass is or at confidence level from two different example datasets. It implies that the radius is km or km. These results are consistent with results from previous studies using similar priors. It has demonstrated the recovery of the EOS of NS using a nonparametric model.

    nucl-thastro-ph.HEastro-ph.SRApJ(2023)·23 citations
  2. 02

    Impact of level densities and -strength functions on -process simulations

    Francesco Pogliano · Ann-Cecilie Larsen

    Studies attempting to quantify the sensitivity of the -process abundances to nuclear input have to cope with the fact that the theoretical models they rely on, rarely come with confidence intervals. This problem has been dealt with by either estimating these intervals and propagating them statistically to the final abundances using reaction networks within simplified astrophysical models, or by running more realistic astrophysical simulations using different nuclear-physics models consistently for all the involved nuclei. Both of these approaches have their strengths and weaknesses. In this work, we run -process calculations for five trajectories using 49 different neutron-capture rate models. Our results shed light on the importance of taking into account shell effects and pairing correlations in the network calculations.

    nucl-thPRC(2023)·9 citations
  3. 03

    Impact of the pre-equilibrium phase for the determination of nuclear geometry in high-energy isobar collisions

    Fernando G. Gardim🇧🇷 · André V. Giannini🇧🇷 · Frédérique Grassi🇧🇷 · Kevin P. Pala🇧🇷 · Willian M. Serenone🇧🇷

    Ultrarelativistic isobar collisions have been proposed as a useful tool to investigate nuclear structure. These systems are not created in equilibrium, rather undergo a pre-thermalization stage. In this stage, some of the initial structure information may be lost and additional effects introduced. The objective of this paper is to study this possibility in the extreme case of a "free-streaming" pre-equilibrium stage. We do this by computing estimators for ratios of various measured (or measurable) quantities (elliptic and triangular flows, mean transverse momentum and associated cumulants, correlators between elliptic or triangular flows and mean transverse momentum, symmetric cumulant and two-plane correlator) and study their sensitivity to the duration of the free-streaming stage. We find that the correlators between elliptic or triangular flows and mean transverse momentum, the so-called and , are indeed sensitive to the duration of the free-streaming stage and that the normalized symmetric cumulant, might also depend on this duration.

    nucl-thhep-phPRC(2024)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE