Effects of the hyperscaling violation and dynamical exponents on the imaginary potential and entropic force of heavy quarkonium via holography

The imaginary potential and entropic force are two important different mechanisms to characterize the dissociation of heavy quarkonia. In this paper, we calculate these two quantities in strongly coupled theories with anisotropic Lifshitz scaling and hyperscaling violation exponent using holographic methods. We study how the results are affected by the hyperscaling violation parameter $$ \theta $$ θ and the dynamical exponent z at finite temperature and chemical potential. Also, we investigate the effect of the chemical potential on these quantities. As a result, we find that both mechanisms show the same results: the thermal width and the dissociation length decrease as the dynamical exponent and chemical potential increase or as the hyperscaling violating parameter decreases.

Improved global α optical model potentials at low energies

Many nuclear astrophysics applications involve radiative α-particle captures, α decays and Qi-particle transfer reactions. Theoretical estimates of the corresponding reaction rates within the framework of the statistical model of Hauser-Feshbach remain highly uncertain due to the poor knowledge of the α-nucleus optical model potential, especially at low energies far below the Coulomb barrier. In the present paper we propose new global α-optical potentials that take into account the strong energy dependence and nuclear structure effects that characterize the alpha-nucleus interaction. The real part of the potential is calculated using a double-folding procedure over the M3KY effective nucleon-nucleon interaction. A Woods-Saxon potential is used for the imaginary potential where now a new parametrization is introduced to describe its energy dependence. Three potentials are developed, one with purely volume absorption, one with volume plus surface absorption, and finally, one where in addition to volume and surface absorption, the dispersive contributions obtained from the dispersive relation are included. The three potentials considered are able to reproduce the bulk of experimental data on (a,7), (α,η), (a,p) and (η,α) reactions as well as the existing elastic scattering data at energies of relevance to astrophysical applications. However, when considering reaction rates for nuclei in the experimentally unexplored mass region, deviations within a factor of 10 are found. These uncertainties are mainly due to the difficulty in constraining the diffuseness of the imaginary potential from analyses of existing experimental data

The dispersion in spherical statistical optical potential (SOM) from the interaction of fast neutrons with197Au nucle

A statistical optical potential has been used to analyze andevaluate the neutron interaction with heavy nuclei 197Au at theneutron energy range (1-20 MeV). Empirical formulae of the opticalpotentials parameters are predicted by using ABAREX Code withminimize accuracy compared with experimental bench work data.The total elastic, absorption, shape elastic and total compound crosssections are calculated for different target nuclei and differentincident neutron energies to predict the appropriate opticalparameters that suit the present interaction. Also the dispersionrelation linking between real and imaginary potential is analyzedwith more accuracy. The results indicate the behavior of thedispersion contribution in imaginary potential has a parabolic changeabout the Fermi surface energy while in the real potential it fall withincreasing the neutron energy. Good agreements have been achievedwith the available experimental data