Nuclear Theory·nucl-th

Tuesday·April 9, 2024

14 papers—5 primary·9 cross-listed

01
[Submitted on 6 Apr 2024]
$K_{1}^{\pm}$ mesons moving in nuclear matter
Seokwoo Yeo🇰🇷 · HyungJoo Kim🇯🇵 · Su Houng Lee🇰🇷
Observing the mass shifts of mesons immersed in nuclear matter is interesting, as the changes are expected to shed light on the effects of chiral symmetry breaking on the origin of hadron masses. At the same time, it is important to understand the momentum dependence of the masses for spin-1 mesons, as the changes manifest differently across the two polarization modes. Here, the mass shifts of $K_{1}^{\pm}$ mesons with finite three-momentum in nuclear medium are studied in the QCD sum rule approach. We find that the mass of $K_{1}^{+}$ ( $K_{1}^{-}$ ) meson is increased(decreased) by the non-trivial momentum effect in both the transverse and longitudinal modes. Specifically, compared to its rest mass in the nuclear medium, in the transverse mode, the mass of $K_{1}^{+} (K_{1}^{-})$ is observed to shift by +2(-55) MeV, while in the longitudinal mode, the mass shift is +13(-11) MeV, all at a momentum of 0.5 GeV. Exploring the medium modifications of $K_{1}$ meson through kaon beams at J-PARC will provide insights on the partial restoration of chiral symmetry in nuclear matter.
Comments:
9 pages, 6 figures, acknowledgments added
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2404.04532 [pdf]
PRD(2024)·3 citations
02
[Submitted on 6 Apr 2024]
Branch-cut in the shear-stress response function of massless $λ φ^{4}$ with Boltzmann statistics
Gabriel S. Rocha · Isabella Danhoni · Kevin Ingles · Gabriel S. Denicol · Jorge Noronha
Using an analytical result for the eigensystem of the linearized collision term for a classical system of massless scalar particles with quartic self-interactions, we show that the shear-stress linear response function possesses a branch-cut singularity that covers the whole positive imaginary semi-axis. This is demonstrated in two ways: (1) by truncating the exact, infinite linear system of linear equations for the rank-two tensor modes, which reveals the cut touching the origin; and (2) by employing the Trotterization techniques to invert the linear response problem. The former shows that the first pole tends towards the origin and the average separation between consecutive poles tends towards zero as power laws in the dimension of the basis. The latter allows one to obtain the response function in closed form in terms of Tricomi hypergeometrical functions, which possess a branch-cut on the above-mentioned semi-axis. This suggests that the presence of a cut along the imaginary frequency axis of the shear stress correlator, inferred from previous numerical analyses of weakly coupled scalar $λ φ^{4}$ theories, does not arise due to quantum statistics but instead emerges from the fundamental properties of this system's interactions.
Comments:
18 pages, 3 figures, v2: published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2404.04679 [pdf]
PRD(2024)·18 citations
03
[Submitted on 7 Apr 2024]
Reconciling the HESS J1731-347 constraints with Parity doublet model
Bikai Gao🇯🇵 · Yan Yan🇨🇳 · Masayasu Harada🇯🇵
The recent discovery of a central compact object (CCO) within the supernova remnant HESS J1731-347, characterized by a mass of approximately $0.7 7_{- 0.17}^{+ 0.20} M_{⊙}$ and a radius of about $10. 4_{- 0.78}^{+ 0.86}$ km, has opened up a new window for the study of compact objects. This CCO is particularly intriguing because it is the lightest and smallest compact object ever observed, raising questions and challenging the existing theories. To account for this light compact star, a mean-field model within the framework of parity doublet structure is applied to describe the hadron matter. Inside the model, part of the nucleon mass is associated with the chiral symmetry breaking while the other part is from the chiral invariant mass $m_{0}$ which is insensitive to the temperature/density. The value of $m_{0}$ affects the nuclear equation of state for uniform nuclear matter at low density and exhibits strong correlations with the radii of neutron stars. We point out that HESS J1731-347 can be explained as the lightest neutron star for $m_{0} ≃ 850$ \,MeV.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2404.04786 [pdf]
PRC(2024)·37 citations
04
[Submitted on 8 Apr 2024]
Microscopic description of induced fission in a configuration interaction approach
K. Uzawa · K. Hagino · G. F. Bertsch
Even though more than 80 years have passed since the discovery of fission, its microscopic understanding has still been unclear. To clarify the underlying mechanics of induced fission, we analyze the distribution of a fission width using a miscropic framework based on a configuration-interaction approach. The distribution is known to follow a chi-squared distribution, which is characterized by the effective number of decay channels, $ν$ . We introduce an effective Hamitonian for the space of compound nucleus states and estimate $ν$ from the rank of the imaginary part of the effective Hamiltonian. Applying the model to $^{235}$ U(n,f), we succesfully reproduce the empirical value of $ν = 2.3 \pm 1.1$ . We also find that $ν$ is insensitve to the number of fission channels, which is consistent with an experimental finding.
Comments:
6 pages, 3 figures, Proceedings of FUSION23
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2404.05500 [pdf]
EPJ Web Conf.(2024)·1 citation
05
[Submitted on 8 Apr 2024]
First-order phase transitions in the cores of neutron stars
Oleg Komoltsev🇳🇴
I explore various scenarios for the phase transition within neutron-star matter. I do so by generating large model-agnostic ensemble using Gaussian processes, both with and without explicit inclusion of first-order phase transitions (FOPTs). The ensemble is conditioned with state-of-the-art astrophysical and theoretical inputs in a fully Bayesian approach. I study how the current data affect the posterior probability of the location and the strength of FOPT. I find that the previously observed peak structure of the sound speed remains stable against inclusion of FOPTs. While the current data cannot differentiate between a smooth crossover and a first-order phase transition, 91% of the total evidence consists of equations of state with some form of phase changes, such as FOPT occurring within or terminating the stable branch of neutron stars, or an indication of a crossover to quark matter.
Comments:
Version 5: Used the corrected version of the Marginalized QCD likelihood function. Plots and Bayes factors changed slightly, but the conclusions remain unchanged. 7 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2404.05637 [pdf]
PRD(2024)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE

K1±​ mesons moving in nuclear matter

Branch-cut in the shear-stress response function of massless λφ4 with Boltzmann statistics

Reconciling the HESS J1731-347 constraints with Parity doublet model

Microscopic description of induced fission in a configuration interaction approach

First-order phase transitions in the cores of neutron stars

Affiliations

$K_{1}^{\pm}$ mesons moving in nuclear matter

Branch-cut in the shear-stress response function of massless $λ φ^{4}$ with Boltzmann statistics