A new analytical solution has been obtained for stellar models by solving Einstein's field equations for the spherically symmetric and static case. The density variation is found to be smooth and positive under all conditions. The authors show that if they change the variable r to x=Cr2, where C is a constant, the field equations are reduced to a form which is easier to solve. Two specific cases, namely P

No abstract

The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier ones are produced by the r-process. Approximately half of the heavy elements with mass number A 70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the r-process in supernovae for the production of heavy elements beyond A = 40 with the newest mass values available. The supernova envelopes at a temperature 10 9 K and neutron density of 10 24 cm −3 are considered to be one of the most potential sites for the r-process. The primary goal of the r-process calculations is to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. We have studied the r-process path corresponding to temperatures ranging from 1.0 × 10 9 K to 3.0 × 10 9 K and neutron density ranging from 10 20 cm −3 to 10 30 cm −3 . With temperature and density conditions of 3.0 × 10 9 K and 10 20 cm −3 a nucleus of mass 273 was theoretically found corresponding to atomic number 115. The elements obtained along the r-process path are compared with the observed data at all the above temperature and density range.

The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier ones are produced by the r-process. Approximately half of the heavy elements with mass number A > 70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the r-process in supernovae for production of heavy elements beyond A = 40 with the newest mass values available. The supernovae envelopes at a temperature >10 9 K and neutron density of 10 24 cm −3 are considered to be one of the most potential sites for the r-process. We investigate the r-process in a site-independent, classical approach which assumes a chemical equilibrium between neutron captures and photodisintegrations followed by a β-flow equilibrium. We have studied the r-process path corresponding to temperatures ranging from 1.0 × 10 9 K to 3.0 × 10 9 K and neutron density ranging from 10 20 cm −3 to 10 30 cm −3 . The primary goal of the r-process calculations is to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. The abundances obtained are compared with supernova explosion condition and found in good agreement. The elements ob-R. Baruah ( ) tained along the r-process path are compared with the observed data at all the above temperature and density range.

Matter and radiation densities are compared with a constant vacuum energy density of positive cosmological constant, from a few seconds of the universe till the present epoch. Epoch of acceleration is calculated by estimating baryonic density from consideration of finite thickness of last scattering surface and dark matter density from inflationary flatness condition. The calculated epoch of acceleration is found to be in good agreement with recent supernova observations.