Nuclear Theory·nucl-th
13 papers—6 primary·7 cross-listed
Semyon Potesnov🇩🇪 · David Wagner🇮🇹
Employing a kinetic framework, we calculate all transport coefficients for relativistic dissipative (second-order) hydrodynamics for arbitrary particle masses in the 14-moment approximation. Taking the non-relativistic limit, it is shown that the relativistic theory reduces to the Grad equations computed in the 'order-of-magnitude' approach.
Jing Ye🇨🇳 · Wei-Zhou Jiang🇨🇳
The zero-sound modes at finite temperature are investigated with the relativistic random phase approximation to signal the uncertainty of the equation of state (EOS) of asymmetric nuclear matter. It is observed that in typically selected stiff and soft relativistic mean-field (RMF) models, zero-sound modes arise at low temperature, whereas increasing the temperature gradually breaks the zero sound in soft models, with a smaller density range compared to stiff models. At high density, the presence or absence of zero sound turns out to be correspondingly the character of the stiff or soft RMF EOS. More strikingly, we find by analyzing the dispersion relation and sound velocity that at finite temperature the zero-sound modes in RMF models with the stiff EOS undergo a thermal bifurcation, resulting in the transform of zero sound into the first sound at some momentum . The thermally bifurcated sound branch in the stiff models and the zero-sound branch in the soft models are both highly sensitive to the slope of the symmetry energy, providing promising signals for the pending high-density symmetry energies. In addition, it is found that there exists a nonlinear dispersion relation for both the stiff and soft models that supports the zero sound in the relatively lower density region.
Muhammad Majid · Jameel-Un Nabi · Gul Daraz
The allowed charge-changing transitions are the most common weak interaction processes of spin-isospin form that play a crucial role in several nuclear/astrophysical processes. The first-forbidden (FF) transition becomes important, in the circumstances where allowed Gamow-Teller (GT) transitions are unfavored, specifically for neutron-rich nuclei due to phase space considerations. In this paper deformed proton-neutron quasi-particle random phase approximation (pn-QRPA) model is applied, for the first time, for the estimation of allowed GT and unique first-forbidden (U1F) transitions (J = 2) of neutron rich copper isotopes in mass range 72 A 82 under stellar conditions. We compared our computed terrestrial -decay half-life values with previous calculations and experimental results. It was concluded that the pn-QRPA calculation is in good accordance with measured data. Our study suggests that the addition of rank (0 and 1) operators in FF transitions can further improve the comparison which remain unattended at this stage. The deformed pn-QRPA model was employed for the estimation of GT and U1F stellar electron emission (-decay) rates over wide range of stellar temperature (0.01 GK -- 30 GK) and density (10 -- 10 g/cm) domains for astrophysical applications. Our study shows that, in high density and low temperature regions, the contribution of U1F rates to total electron emission rates of neutron-rich copper nuclei is negligible.
Jameel-Un Nabi · Muhammad Majid
Charge-changing transitions play a significant role in stellar weak-decay processes. The fate of the massive stars is decided by these weak-decay rates including lepton (positron and electron) captures rates, which play a consequential role in the dynamics of core collapse. As per previous simulation results, weak interaction rates on nickel isotopes have significant influence on the stellar core vis--vis controlling the lepton content of stellar matter throughout the silicon shell burning phases of high mass stars up to the presupernova stages. In this paper we perform a microscopic calculation of Gamow-Teller charge-changing transitions, in the -decay and electron capture directions, for neutron-rich nickel isotopes (Ni). We further compute the associated weak-decay rates for these selected nickel isotopes in stellar environment. The computations are accomplished by employing the deformed proton-neutron quasiparticle random phase approximation (pn-QRPA) model. A recent study showed that the deformed pn-QRPA theory is well suited for the estimation of Gamow-Teller transitions. The astral weak-decay rates are determined over densities in the range of 10 -- 10g/cm and temperatures in the range of 0.0110 -- 3010K. The calculated lepton capture rates are compared with the previous calculation of Pruet and Fuller. The overall comparison demonstrates that, at low stellar densities and high temperatures, our electron captures rates are bigger by as much as two orders of magnitude. Our results show that, at higher temperatures, the lepton capture rates are the dominant mode for the stellar weak rates and the corresponding lepton emission rates may be neglected.
Jameel-Un Nabi🇵🇰 · Mahmut Boyukata🇨🇭
The structure and the weak interaction mediated rates of the heavy waiting point (WP) nuclei Zr, Mo, Ru, Pd and Cd along line were studied within the interacting boson model-1 (\mbox{IBM-1}) and the proton-neutron quasi-particle random phase approximation (\mbox{pn-QRPA}). The energy levels of the = WP nuclei were calculated by fitting the essential parameters of \mbox{IBM-1} Hamiltonian and their geometric shapes were predicted by plotting potential energy surfaces (PESs). Half-lives, continuum electron capture rates, positron decay rates, electron capture cross sections of WP nuclei, energy rates of -delayed protons and their emission probabilities were later calculated using the \mbox{pn-QRPA}. The calculated Gamow-Teller strength distributions were compared with previous calculation. We present positron decay continuum electron capture rates on these WP nuclei under -process conditions using the same model. For the -process conditions, the calculated total weak rates are twice the Skyrme HF+BCS+QRPA rates for Zr. For remaining nuclei the two calculations compare well. The electron capture rates are significant and compete well with the corresponding positron decay rates under -process conditions. The finding of the present study supports that electron capture rates form an integral part of the weak rates under -process conditions and has an important role for the nuclear model calculations.
Ashutosh Dwibedi · Dushmanta Sahu · Jayanta Dey · Kangkan Goswami · Sabyasachi Ghosh · Raghunath Sahoo
The Lagrangian for strongly interacting and rotating quark matter is modified with the inclusion of the spinorial connections, which in turn affect the thermodynamic equation of state and transport properties of the medium. In this work, we investigate the transport properties of quark matter under finite rotation, focusing specifically on electrical conductivity and shear viscosity by using a two-flavor Nambu--Jona-Lasinio (NJL) model. The chiral condensate in the NJL model decreases under rotation, leading to enhanced transport properties. Moreover, rotation induces anisotropy in the transport coefficients, which are calculated within the kinetic theory framework using the Boltzmann transport equation. The Coriolis force is introduced in the force term of the Boltzmann transport equation, like the Lorentz force, which is considered for finite magnetic fields. By using a phenomenological temperature-dependent angular velocity, we observe that the variation of anisotropic components with temperature preserves the traditional valley-shaped pattern. However, the magnitude of the anisotropic components is suppressed compared to the usual component one finds in the absence of rotation. Interestingly, at zero net quark density, Hall-like transport phenomena emerge as significant non-dissipative contributions under rotation, which is not expected under finite magnetic fields due to the cancellation of quark and anti-quark Hall currents.
first authorsco-authorsvia INSPIRE