Narrow Results

A new class of solutions describing analytical solutions for compact stellar structures has been developed within the tenets of General Relativity. Considering the inherent anisotropy in compact stars, a stable and causal model for realistic anisotropic neutron stars was obtained using the general theory of relativity. Assuming a physically acceptable nonsingular form of one metric potential and radial pressure containing the curvature parameter $R$, the constant $k$ and the radius $r$, analytical solutions to Einstein’s field equations for anisotropic matter distribution were obtained. Taking the value of $k$ as −0.44, it was found that the proposed model obeys all necessary physical conditions, and it is potentially stable and realistic. The model also exhibits a linear equation of state, which can be applied to describe compact stars.

An interesting method of obtaining the equation of state for nuclear matter, from a density dependent M3Y interaction, by minimizing the energy per nucleon is described. The density dependence parameters of the interaction are obtained by reproducing the saturation energy per nucleon and the saturation density of spin and isospin symmetric cold infinite nuclear matter. The nuclear matter equation of state thus obtained is then used to calculate the pressure, energy density, nuclear incompressibility and velocity of sound in nuclear medium. The results obtained are in good agreement with experimental data and provide a unified description of radioactivity, scattering and nuclear matter.

The estimate of the energy deposition rate (EDR) for neutrino pair annihilation has been carried out. The EDR for the neutrinos coming from the equatorial plane of a rotating neutron star is calculated along the rotation axis using the Cook–Shapiro–Teukolsky metric. The neutrino trajectories and hence the neutrinos emitted from the disk are affected by the redshift due to disk rotation and gravitation. The EDR is very sensitive to the value of the temperature and its variation along the disk. The rotation of the star has a negative effect on the EDR; it decreases with increase in rotational velocity.

We study the effects of isovector-scalar ($\delta$)-meson on neutron and hyperon stars. Influence of $\delta$-meson on both static and rotating stars is discussed. The $\delta$-meson in a neutron star consisting of protons, neutrons and electrons, makes the equations of states (EOS) stiffer at higher density, and consequently increases the maximum mass of the star. But induction of $\delta$-meson in the hyperon star decreases the maximum mass. This is due to the early evolution of hyperons in presence of $\delta$-meson.

A noninteracting hadron resonance gas model is used often to study the hadronic phase formed in heavy ion collisions. Interaction among various hadronic constituents can be included using an S-matrix-based virial expansion approach. The virial coefficients require the dynamical information about the scattering phase shifts, which is used to compute various thermodynamic observables of an interacting hadronic gas. The attractive part of the phase shifts are calculated using K-matrix formalism while the repulsive part is obtained by fitting to experimental data. Calculation of various thermodynamic variables like pressure, energy density, specific heat capacity, etc., along with the second and higher-order correlations and fluctuations of conserved charges are done, first with only attraction and then with both attraction and repulsion included. Comparison of S-matrix results indicate a better agreement with lattice QCD data than the ideal HRG model across all thermodynamic variables.

The nucleon–nucleon (NN) potential is the residual interaction of the strong interaction in the low-energy region and is also the fundamental input to the study of atomic nuclei. Based on the nonperturbative properties of the quantum chromodynamics (QCD), NN potential is not yet directly accessible from QCD theory. Therefore, various models of NN interactions have been constructed based on Yukawa’s meson exchange pictures since the 1930s, including one-boson-exchange models, coordinate operator models and chiral effective field models. Analysis of extensive NN scattering data has shown that the two-body nuclear force exhibits a short-range repulsion and intermediate-range attraction, and decays rapidly with increasing distance. A series of charge-dependent high-precision NN interactions have been further developed in the past 30 years such as the AV18 potential, CD-Bonn potential, pvCD-Bonn potentials and the chiral effective nuclear potentials with momentum expansion up to the fifth order. In this work, the phase shifts at different channels, the cross-sections, the entanglement entropy in spin space, and the equations of state of symmetric nuclear matter and pure neutron matter from these high-precision NN interactions are calculated and systematically compared. It can be found that they have significant differences in the cases with high-angular momentum, high-laboratory energy and high-density regions.

A simple and straightforward theoretical model is developed to investigate the elastic constants of alkaline earth oxide solids under the effect of temperature. The calculation are performed with the help of high temperature equation of state (EOS) derived from Tallon's method based on thermodynamic analysis. The results obtained for these solids are discussed and compared with experimental data under the effect of high temperature. The results are found to be in good agreement with available experimental results

Recent results on multi-strange and heavy flavor production at RHIC are discussed and compared with model predictions. The idea of heavy flavor collectivity and light flavor thermalization is presented in the light of recent heavy flavor measurement at RHIC.