Cosmic Evolution in Generalised Brans-Dicke Theory

We have studied the Generalised Brans-Dicke theory and obtained exact solutions of a(t),phi(t),and omega(t) for different epochs of the cosmic evolution .We discuss how inflation,decceleration,cosmic acceleration can result from this solution.The time variation of G(t) is also examined.Comment: 12 pages, no figure

CFD analysis of heat transfer in a helical coil heat exchanger with constant wall heat transfer coefficient

There is a wide application of coiled heat exchanger in the field of cryogenics and other industrial applications for its enhanced heat transfer characteristics and compact structure. Lots of researches are going on to improve the heat transfer rate of the helical coil heat exchanger. Here, in this work, an analysis has been done for a tube-in-tube helical heat exchanger with constant heat transfer coefficient with turbulent flow. There are various factors present that may affect the heat transfer characteristics of the heat exchanger. Here, the experiment has been done by varying the curvature ratio i.e. ratio of coil diameter to inner tube diameter and inlet velocity of the hot fluid in the inner tube. The curvature ratio is varied from 8 to 25 and inlet velocity is varied from 1m/s to 2m/s step wise. The analysis has done using ANSYS 13 CFD methodology. Different parameters are calculated from the results obtained and graphs are plotted between various parameters such as Nusselt number, friction factor, pressure drop and pumping power versus Reynolds number. These graphs have been analyzed and discussed to find out the optimal result for which the heat exchanger would give the best performance

Application of Relativistic Coupled-cluster Theory to Electron Impact Excitations of Mg+^+ in the Plasma Environment

A relativistic coupled-cluster (RCC) theory is implemented to study electron impact excitations of atomic species. As a test case, the electron impact excitations of the $3s ~ ^2S_{1/2} - 3p ~ ^2P_{1/2;3/2}$ resonance transitions are investigated in the singly charged magnesium (Mg$^+$) ion using this theory. Accuracies of wave functions of Mg$^+$ are justified by evaluating its attachment energies of the relevant states and compared with the experimental values. The continuum wave function of the projectile electron are obtained by solving Dirac equations assuming distortion potential as static potential of the ground state of Mg$^+$. Comparison of the calculated electron impact excitation differential and total cross-sections with the available measurements are found to be in very good agreements at various incident electron energies. Further, calculations are carried out in the plasma environment in the Debye H\"uckel model framework, which could be useful in the astrophysics. Influence of plasma strength on the cross-sections as well as linear polarization of the photon emission in the $3p ~ ^2P_{3/2} - 3s ~ ^2S_{1/2}$ transition is investigated for different incident electron energies.Comment: 9 pages, 1 table and 3 figure

Effect of both Z and Z'-mediated flavor-changing neutral currents on the baryonic rare decay lambdablambda_b decays into lambdal+l−lambda l^+l^-

We study the effect of both Z and Z'-mediated flavor-changing neutral currents (FCNCs) on the $lambda_b arrow lambda l^+l^- (l = mu, tau)$ rare decay. We find the branching ratio is reasonably enhanced from its standard model value due to the effect of both Z and Z'-mediated FCNCs, and gives the possibility of new physics beyond the standard model. The contribution of Z'-boson depends upon the precise value of the mass of Z' boson.Comment: 14 page

On some strategies using auxiliary information for estimating finite population mean

This paper presents an empirical investigation of the performance of five strategies for estimating the finite population mean using parameters such as mean or variance or both of an auxiliary variable. The criteria used for the choices of these strategies are bias, efficiency and approach to normality (asymmetry)