Nuclear Theory·nucl-th

Friday·July 17, 2020

9 papers—4 primary·5 cross-listed

01
Excluded-volume model for quarkyonic matter II: Three-flavor shell-like distribution of baryons in phase space
Dyana C. Duarte🇺🇸 · Saul Hernandez-Ortiz🇺🇸 · Kie Sang Jeong🇺🇸
We extend the excluded-volume model of isospin symmetric two-flavor dense quarkyonic matter [Phys. Rev. C 101, 035201 (2020)] including strange particles and address its implications for neutron stars. The effective sizes of baryons are defined from the diverging hard-core potentials in the short interdistance regime. Around the hard-core density, the repulsive core between baryons at short distances leads to a saturation in the number density of baryons and generates perturbative quarks from the lower phase space, which leads to the shell-like distribution of baryons by the Pauli exclusion principle. The strange-quark Fermi sea always appears at high densities but the $Λ$ hyperon shell only appears when the effective size of the $Λ$ hyperon is smaller than the effective size of nucleons. We find that the pressure of strange quarkyonic matter can be large enough to support neutron stars with two times solar mass and can have a large sound speed, $c_{s}^{2} ≃ 0.7$ . The fraction of the baryon number carried by perturbative quarks is about 30% at the inner core of most massive neutron stars.
nucl-thhep-phPRC(2020)·35 citations
02
Second-forbidden nonunique $β^{-}$ decays of $^{24}$ Na and $^{36}$ Cl assessed by the nuclear shell model
Anil Kumar · Praveen C. Srivastava · Joel Kostensalo · Jouni Suhonen
We have performed a systematic study of the log $f t$ values, shape factors and electron spectra for the second-forbidden nonunique $β^{-}$ decays of $^{24}$ Na $(4^{+}) \to^{24}$ Mg $(2^{+})$ and $^{36}$ Cl $(2^{+}) \to^{36}$ Ar $(0^{+})$ transitions under the framework of the nuclear shell model. We have performed the shell model calculations in the $s d$ model space, using more recent microscopic effective interactions such as Daejeon16, chiral N3LO, and JISP16. These interactions are derived from the no-core shell model wave functions using Okubo-Lee-Suzuki transformation.For comparison, we have also shown the results obtain from the phenomenological USDB interaction. To test the predictive power of these interactions first we have computed low-lying energy spectra of parent and daughter nuclei involved in these transitions. The computed results for energy spectra, nuclear matrix elements, log $f t$ values, shape factors, electron spectra and decomposition of the integrated shape factor are reported and compare with the available experimental data.
nucl-thnucl-exPRC(2020)·36 citations
03
Possibilities of direct production of superheavy nuclei with Z=112--118 in different evaporation channels
J. Hong · G. G. Adamian · N. V. Antonenko · P. Jachimowicz · M. Kowal
The production cross sections of heaviest isotopes of superheavy nuclei with charge numbers 112--118 are predicted in the $x n$ --, $p x n$ --, and $α x n$ --evaporation channels of the $^{48}$ Ca-induced complete fusion reactions for future experiments. The estimates of synthesis capabilities are based on a uniform and consistent set of input nuclear data. Nuclear masses, deformations, shell corrections, fission barriers, and decay energies are calculated within the macroscopic-microscopic approach for even-even, odd-Z, and odd-N nuclei. For odd systems, the blocking procedure is used. To find, the ground states via minimization and saddle points using Immersion Water flow technique, multidimensional deformation spaces, containing non-axially are used. As shown, current calculations based on a new set of mass and barriers, agree very well with experimentally known cross-sections, especially in the $3 n$ --evaporation channel. The dependencies of these predictions on the mass/fission barriers tables and fusion models are discussed. A way is shown to produce directly unknown superheavy isotopes in the $1 n$ -- or $2 n$ --evaporation channels. The synthesis of new superheavy isotopes unattainable in reactions with emission of neutrons is proposed in the promising channels with emission of protons ( $σ_{p x n} ≃ 10 - 200$ fb) and alphas ( $σ_{α x n} ≃ 5 - 500$ fb).
nucl-thPLB(2020)·18 citations
04
Nucleon polarizabilities in covariant baryon chiral perturbation theory with explicit $Δ$ degrees of freedom
M. Thürmann🇩🇪 · E. Epelbaum🇩🇪 · A. M. Gasparyan🇩🇪 · H. Krebs🇩🇪
We compute various nucleon polarizabilities in chiral perturbation theory implementing the $Δ$ -full ( $Δ$ -less) approach up to order $ϵ^{3} + q^{4}$ ( $q^{4}$ ) in the small-scale (chiral) expansion. The calculation is carried out using the covariant formulation of $χ$ PT by utilizing the extended on-mass shell renormalization scheme. Except for the spin-independent dipole polarizabilities used to fix the values of certain low-energy constants, our results for the nucleon polarizabilities are pure predictions. We compare our calculations with available experimental data and other theoretical results. The importance of the explicit treatment of the $Δ$ degree of freedom in the effective field theory description of the nucleon polarizabilities is analyzed. We also study the convergence of the $1/ m$ expansion and analyze the efficiency of the heavy-baryon approach for the nucleon polarizabilities.
nucl-thPRC(2021)·13 citations
05
Hybrid stars from a three-flavor NJL model with two kinds of tensor condensates
M. Morimoto🇯🇵 · Y. Tsue🇯🇵 · J. da Providencia🇵🇹 · C. Providencia🇵🇹 · M. Yamamura🇯🇵
To obtain the equation of state of quark matter and construct hybrid stars, we calculate the thermodynamic potential in the three-flavor Nambu-Jona-Lasinio model including the tensor-type four-point interaction and the Kobayashi-Maskawa-'t Hooft interaction. To construct the hybrid stars, it is necessary to impose the beta-equilibrium and charge neutrality conditions on the system. It is shown that tensor condensed phases appear at large chemical potential. Under the possibility of the existence of the tensor condensates, the relationship between the radius and mass of hybrid stars is estimated.
↳ hep-phnucl-thIJMPE(2020)·2 citations
06
Exact equilibrium distributions in statistical quantum field theory with rotation and acceleration: scalar field
F. Becattini🇮🇹 · M. Buzzegoli🇮🇹 · A. Palermo (University of Florence and INFN)🇮🇹
We derive a general exact form of the phase space distribution function and the thermal expectation values of local operators for the free quantum scalar field at equilibrium with rotation and acceleration in flat space-time without solving field equations in curvilinear coordinates. After factorizing the density operator with group theoretical methods, we obtain the exact form of the phase space distribution function as a formal series in thermal vorticity through an iterative method and we calculate thermal expectation values by means of analytic continuation techniques. We separately discuss the cases of pure rotation and pure acceleration and derive analytic results for the stress-energy tensor of the massless field. The expressions found agree with the exact analytic solutions obtained by solving the field equation in suitable curvilinear coordinates for the two cases at stake and already - or implicitly - known in literature. In order to extract finite values for the pure acceleration case we introduce the concept of analytic distillation of a complex function. For the massless field, the obtained expressions of the currents are polynomials in the acceleration/temperature ratios which vanish at $2 π$ , in full accordance with the Unruh effect.
↳ hep-thcond-mat.stat-mechgr-qcmath-ph+2JHEP(2021)·52 citations
07
Production of Light Nuclei in Heavy Ion Collisions via Hagedorn Resonances
Kai Gallmeister🇩🇪 · Carsten Greiner (Goethe University, Frankfurt am Main)🇩🇪
The physical processes behind the production of light nuclei in heavy ion collisions are unclear. The nice theoretical description of experimental yields by thermal models conflicts with the very small binding energies of the observed states, being fragile in such a hot and dense environment. Other available ideas are delayed production via coalescence, or a cooling of the system after the chemical freeze-out according a Saha equation, or a `quench' instead of a thermal freeze-out. A recently derived prescription of an (interacting) Hagedorn gas is applied to consolidate the above pictures. The tabulation of decay rates of Hagedorn states into light nuclei allows to calculate yields usually unaccessable due to very poor Monte Carlo statistics. Decay yields of stable hadrons and light nuclei are calculated. While the scale-free decays of Hagedorn states alone are not compatible with the experimental data, a thermalized hadron and Hagedorn state gas is able to describe the experimental data. Applying a cooling of the system according a Saha-equation with conservation of nucleons and anti-nucleons in number leads to (nearly) temperature independent yields, thus a production of the light nuclei at temperatures much lower than the chemical freeze-out temperature is possible.
↳ hep-phnucl-thEPJA(2021)·6 citations
08
Field of a moving locked charge in classical electrodynamics
Alexander J. Silenko🇨🇳
The paradox of a field of a moving locked charge (confined in a closed space) is considered and solved with the use of the integral Maxwell equations. While known formulas obtained for instantaneous fields of charges moving along straight and curved lines are fully correct, measurable quantities are average electric and magnetic fields of locked charges. It is shown that the average electric field of locked charges does not depend on their motion. The average electric field of protons moving in nuclei coincides with that of protons being at rest and having the same spatial distribution of the charge density. The electric field of a twisted electron is equivalent to the field of a centroid with immobile charges which spatial distribution is defined by the wave function of the twisted electron.
↳ physics.class-phhep-phnucl-thMod.Phys.Lett.A(2020)·1 citation
09
GW190814 as a massive rapidly-rotating neutron star with exotic degrees of freedom
V. Dexheimer🇺🇸 · R.O. Gomes🇩🇪 · T. Klähn🇺🇸 · S. Han🇺🇸 · M. Salinas🇺🇸
In the context of the massive secondary object recently observed in the compact-star merger GW190814, we investigate the possibility of producing massive neutron stars from a few different equation of state models that contain exotic degrees of freedom, such as hyperons and quarks. Our work shows that state-of-the-art relativistic mean field models can generate massive stars reaching $≳ 2.05 \Msun$ , while being in good agreement with gravitational-wave events and x-ray pulsar observations, when quark vector interactions and non-standard self-vector interactions are introduced. In particular, we present a new version of the Chiral Mean Field (CMF) model in which a different quark-deconfinement potential allows for stable stars with a pure quark core. When rapid rotation is considered, our models generate stellar masses that approach, and in some cases surpass $2.5 \Msun$ . We find that in such cases fast rotation does not necessarily suppress exotic degrees of freedom due to changes in stellar central density, but require a larger amount of baryons than what is allowed in the non-rotating stars. This is not the case for pure quark stars, which can easily reach $2.5 \Msun$ and still possess approximately the same amount of baryons as stable non-rotating stars. We also briefly discuss possible origins for fast rotating stars with a large amount of baryons and their stability, showing how the event GW190814 can be associated with a star containing quarks as one of its progenitors.
↳ astro-ph.HEastro-ph.SRnucl-thPRC(2021)·176 citations

Affiliations

first authorsco-authorsvia INSPIRE