Nuclear Theory·nucl-th

Friday·December 29, 2023

22 papers—10 primary·12 cross-listed

01
[Submitted on 23 Dec 2023]
Time Scales in Many-Body Fast Neutrino Flavor Conversion
Ramya Bhaskar🇺🇸 · Alessandro Roggero🇺🇸 · Martin J. Savage🇺🇸
Time scales associated with many-body fast neutrino flavor conversions in core-collapse supernova are explored in the context of an effective two-flavor model with axial symmetry. We present a preliminary study of time scales obtained from a linear stability analysis and from the distributions of Loschmidt echo crossing times (intimately connected to dynamical phase transitions in non-equilibrium systems) determined by time evolution with the exact many-body Hamiltonian. Starting from a tensor-product initial state describing systems of $N$ neutrinos, with $N /2$ electron-type and $N /2$ heavy-type, with uniform angular distributions, the Loschmidt echo crossing times, $t_{L_{\times}}$ , are found to exhibit two distinct time scales that are exponentially separated. The second peak structure at longer times, effectively absent for $N = 4$ , develops with increasing $N$ . When re-scaled in terms of $lo g t_{L_{\times}}$ , the distributions are found to become increasingly well described by the sum of two stable distributions. The distribution of Loschmidt echo crossing times differs somewhat from the results of the (numerical) linear stability analysis, which exhibits a peak at finite frequency and a second peak consistent with zero frequency. The exact analysis suggests that the zero-frequency instability manifests itself as a modest flavor-conversion time scale.
Comments:
13 pages, 5 figures; Updated references, and acknowledgments section
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2312.16212 [pdf]
8 citations
02
[Submitted on 27 Dec 2023]
Frame transformation and stable-causal hydrodynamic theory
Sayantani Bhattacharyya🇬🇧 · Sukanya Mitra🇮🇳 · Shuvayu Roy🇮🇳
In this work, a connection has been indicated between the different existing formulations of relativistic hydrodynamic theories, which, in order to be causal and stable, (i) either requires `non-fluid' variables apart from velocity and temperature to be promoted to new degrees of freedom, or, (ii) needs to be in a generalized hydrodynamic frame other than those given by Landau or Eckart. The BDNK stress tensor (originally in a general frame) has been rewritten in the Landau frame using linearized all-order gradient-corrected redefinitions of the temperature and velocity fields. The redefinitions indicate that, while the BDNK formalism has a finite number of derivatives in the general frame, when written in the Landau frame, it either has an infinite number of derivatives, or one has to introduce MIS-like `non-fluid' variables by summing the infinite number of derivatives in the field redefinitions. There can be non-unique ways of performing these infinite-order summations. Finally, the dispersion relations and the corresponding spectra of these different systems of MIS type equations have been analyzed to check that the systems of equations presented here are indeed equivalent to the BDNK formalism, at least in the hydrodynamic regime.
Comments:
28 pages
Subjects:
Nuclear Theory (nucl-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2312.16407 [pdf]
10 citations
03
[Submitted on 28 Dec 2023]
Multiphoton fusion of light nuclei in intense laser fields
Binbing Wu · Zhengfeng Fan · Difa Ye · Tao Ye · Congzhang Gao · Chengxin Yu · Xuefeng Xu · Cunbo Zhang · Jie Liu
We investigate the fusion cross sections of light nuclei in the presence of linearly polarized intense laser fields. By combining the Coulomb-Volkov solutions with the complex spherical square-well nuclear potential, we derive an explicit formulation of the multiphoton cross section in a self-consistent manner. Our analysis is specifically focused on deuteron-triton (DT) and proton-boron (p $^{11} B$ ) fusion reactions, both of which have garnered widespread attention. The theoretical results reveal that, under conditions of longer laser wavelengths and lower incident particle kinetic energies, a few thousands of photons can participate in the fusion reactions, resulting in a substantial enhancement of fusion cross sections by almost ten orders of magnitude. We elucidate the multiphoton mechanism underlying these findings and discuss their implications.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2312.16777 [pdf]
PRC(2024)·6 citations
04
[Submitted on 28 Dec 2023]
The mixed phase quark core in massive hybrid stars
Xuhao Wu🇨🇳 · Peng-Cheng Chu🇨🇳 · Min Ju🇨🇳 · He Liu🇨🇳
We investigate the properties of hybrid star and the mixed phase core to explore the radius ratio of the mixed phase in hybrid star. In the context of observed massive neutron stars (NSs), we examine the internal structure, phase transitions, and the impacts of the equation of state (EOS) in maximum hybrid star. We investigate the stiffness changes in the EOS during the hadron-quark phase transition within the hybrid stars. The relativistic mean-field (RMF) model is used to describe hadronic matter, while to the represent quark matter, the Nambu-Jona-Lasinio (NJL) model is applied. We explore the strength of vector coupling in quark matter, which delays the onset density of the mixed phase and reduces the size of the mixed-phase core in a hybrid star, but does not exhibit a clear correlation with the central density. In a hybrid star with a maximum mass of approximately 2 solar masses ( $M_{⊙}$ ), a mixed-phase core of $\sim$ 5 km may exist, comprising about $40%$ of the total radius. However, our results do not support the existence of a sizable quark core containing the mixed phase ( $R_{MP} > 1/2 R_{total}$ ) for the maximum-mass hybrid star or for a 2~ $M_{⊙}$ massive star.
Comments:
9 fighres
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2312.16843 [pdf]
EPJC(2025)·5 citations
05
[Submitted on 28 Dec 2023]
Spin alignment of vector mesons by second-order hydrodynamic gradients
Avdhesh Kumar🇹🇼 · Philipp Gubler🇹🇼 · Di-Lun Yang🇯🇵
Starting with the polarization dependent Wigner function of vector mesons, we derive an expression for the 00-component ( $ρ_{00}$ ) of spin density matrix in terms of the second order gradients of the vector meson distribution functions. We further apply a thermal model to analyze the transverse momentum and the azimuthal angle dependence of $ρ_{00}$ for $ϕ$ and $K^{* 0}$ mesons resulting from distribution gradients in Au-Au collisions with $s_{N N} = 130$ GeV at mid-rapidity. Our results for the transverse momentum dependence indicate that the deviations of $ρ_{00}$ from $1/3$ as the signal for spin alignment are greatly enhanced at large transverse momenta and have a strong centrality dependence while analysis of the azimuthal angle ( $ϕ_{q}$ ) dependence suggest that such deviations have a $cos (2 ϕ_{q})$ structure with opposite sign for $ϕ$ and $K^{* 0}$ . Our finding may be considered as a baseline for probing spin-alignment mechanisms beyond hydrodynamic gradients.
Comments:
30 pages, 3 figures, minor revisions, journal version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2312.16900 [pdf]
PRD(2024)·35 citations
06
[Submitted on 28 Dec 2023]
Constraining the p{\Lambda} interaction from a combined analysis of scattering data and correlation functions
D. L. Mihaylov🇩🇪 · J. Haidenbauer🇩🇪 · V. Mantovani Sarti🇩🇪
This work provides the first combined analysis of low-energy p $Λ$ scattering, considering both cross section and correlation data. The obtained results establish the most stringent constraints to date on the two-body p $Λ$ interaction, pointing to a weaker attraction than so far accepted. The best set of scattering lengths for the spin singlet and triplet are found to range from $f_{0}, f_{1} = (2.1, 1.56)$ to $(3.34, 1.18)$ fm. With a chiral NY potential fine-tuned to those scattering parameters, the in-medium properties of the $Λ$ are explored and a potential depth of $U_{Λ} = - 36.3 \pm 1.3 (stat)_{- 6.2}^{+ 2.5} (syst)$ MeV is found at nuclear matter saturation density.
Comments:
The initial upload contained a wrong entry in Table 1. The 'f1' for point iv) was WRONGLY written as 1.54 fm, whereas the CORRECT value is 1.32 fm
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2312.16970 [pdf]
PLB(2024)·25 citations
07
[Submitted on 28 Dec 2023]
Production of super-heavy nuclei in hot-fusion reactions
V. Yu. Denisov
A model for hot-fusion reactions leading to the synthesis of super-heavy nuclei is discussed. The values of the hot-fusion cross-sections obtained in the model agree with the available experimental data. The hot-fusion cross-sections are found for two different models of the fission barrier heights of super-heavy nuclei. The calculations of the cross-sections for the various hot-fusion reactions leading to the 119 and 120 elements are presented. Simple expressions useful for qualitative analysis of the cross-section for forming super-heavy nuclei are obtained. It is shown that the super-heavy nuclei production cross section is proportional to the transmission coefficient of the capture barrier, realization probability of the $x n$ -evaporation channel, and exponentially depends on the quasi-elastic barrier, fusion reaction Q-value, compound nucleus formation barrier, neutron separation energies, and fission barrier heights.
Comments:
16 pages, 12 figures, 1 table. arXiv admin note: text overlap with arXiv:2309.14995
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2312.17084 [pdf]
PRC(2024)·9 citations
08
[Submitted on 28 Dec 2023]
Two-flavor color superconducting quark stars may not exist
Wen-Li Yuan🇨🇳 · Ang Li🇨🇳
Large uncertainties in the determinations of the equation of state of dense stellar matter allow the intriguing possibility that the bulk quark matter in beta equilibrium might be the true ground state of the matter at zero pressure. And quarks will form Cooper pairs very readily since the dominant interaction between quarks is attractive in some channels. As a result, quark matter will generically exhibit color superconductivity, with the favored pairing pattern at intermediately high densities being two-flavor pairing. In the light of several possible candidates for such self-bound quark stars, including the very low-mass central compact object in supernova remnant HESS J1731-347 reported recently, we carry out one field-theoretic model, the Nambu-Jona-Lasinio model, of investigation on the stability of beta-stable two-flavor color superconducting (2SC) phase of quark matter, nevertheless find no physically-allowed parameter space for the existence of 2SC quark stars.
Comments:
13 pages, 6 figures, with appendix; ApJ (2024) accepted
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2312.17102 [pdf]
ApJ(2024)·18 citations
09
[Submitted on 28 Dec 2023]
Extended Skyrme effective interactions for transport model and neutron stars
Si-Pei Wang🇨🇳 · Rui Wang🇮🇹 · Jun-Ting Ye🇨🇳 · Lie-Wen Chen🇨🇳
It is important to develop a unified theoretical framework to describe the nuclear experiments and astrophysical observations based on the same effective nuclear interactions. Based on the so-called Skyrme pseudopotential up to next-to-next-to-next-to-leading order, we construct a series of extended Skyrme interactions by modifying the density-dependent term and fitting the empirical nucleon optical potential up to above $1$ GeV, the empirical properties of isospin symmetric nuclear matter, the microscopic calculations of pure neutron matter and the properties of neutron stars from astrophysical observations. The modification of the density-dependent term in the extended Skyrme interactions follows the idea of Fermi momentum expansion and this leads to a highly flexible density behavior of the symmetry energy. In particular, the values of the density slope parameter $L$ of the symmetry energy for the new extended Skyrme interactions range from $L = - 5$ MeV to $L = 125$ MeV by construction, to cover the large uncertainty of the density dependence of the symmetry energy. Furthermore, in order to consider the effects of isoscalar and isovector nucleon effective masses, we adjust the momentum dependency of the single-nucleon optical potential and the symmetry potential of these new extended Skyrme interactions and construct a parameter set family, by which we systematically study the impacts of the symmetry energy and the nucleon effective masses on the properties of nuclear matter and neutron stars. The new extended Skyrme interactions constructed in the present work will be useful to determine the equation of state of isospin asymmetric nuclear matter, especially the symmetry energy, as well as the nucleon effective masses and their isospin splitting, in transport model simulations for heavy-ion collisions, nuclear structure calculations and neutron star studies.
Comments:
38 pages, 16 figures, 8 tables. Discussions added and typos fixed. Accepted version to appear in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2312.17105 [pdf]
PRC(2024)·19 citations
10
[Submitted on 28 Dec 2023]
QGP Physics from Attractor Perturbations
Xin An🇵🇱 · Michał Spaliński🇵🇱
The strong longitudinal expansion characteristic of heavy-ion collisions leads to universal attractor behavior of the resulting drop of quark-gluon plasma (QGP) already at very early times. Assuming approximate boost invariance and neglecting transverse expansion at the initial time, we incorporate subsequent transverse dynamics of this system by linearizing the Mueller-Israel-Stewart theory around the transversely homogeneous attractor. The result is a system of coupled ordinary differential equations which describes the proper-time evolution of Fourier modes encoding the transverse structure of the initial energy deposition. The late-time asymptotic behavior of these solutions is described by transseries which make manifest the stability of the attractor against transverse perturbations. In this framework, information about the structure of the plasma in the transverse plane resides mostly in exponentially suppressed corrections to evolution along the attractor, which are not yet negligible at freeze-out. These findings also suggest a simple numerical approach to QGP dynamics using a finite number of Fourier modes. Physical observables can be expressed in terms of the asymptotic data evaluated at freeze-out. We demonstrate the efficacy of this approach by calculating the final multiplicity distributions and collective flow coefficients.
Comments:
A much expanded version, which includes extended discussions and a calculation of flow coefficients. 30 pages and 7 figures. Accepted for publication in PRD
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2312.17237 [pdf]
PRD(2024)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE