Joydev Lahiri

Superconducting gap ratio and isotope-shift exponent in a pair-tunneling model

Abstract The superconducting transition temperature ( T c ), superconducting gap ratio and isotope-shift exponent ( α ) are studied in a narrow band system with a two-dimensional band structure assuming an intra-plane pairing kernel, due to electron–phonon interactions and an interlayer tunneling of Cooper pairs for both isotropic s-wave and d-wave pairing. The pair-tunneling process enhances T c and the gap ratio while lowers α for both cases. The effect of an extended van Hove singularity in the electronic density of states on the gap ratio and α is investigated. The results are compared with the experimental findings of high- T c cuprates.

Angular distributions of neutron-nucleus collisions

We derive the total and the differential cross sections with respect to angle for neutron-induced reactions from an analytical model having a simple functional form to demonstrate the quantitative agreement with the measured cross sections. The energy dependence of the neutron-nucleus interaction cross sections are estimated successfully for energies ranging from 5 to 600 MeV. In this work, the effect of the imaginary part of the nuclear potential is treated more appropriately compared to our earlier work. The angular distributions for neutron scattering also agree reasonably well with the experimental data at forward angles.

Erratum: Cross sections of neutron-induced reactions [Phys. Rev. C 82, 044613 (2010)]

The first equation of Eqs.(3) in [1] was used to describe the mass number and energy dependence of experimental total neutron cross sections for the first time in [2], while the second and third ones for scattering and reaction cross sections in [3]. We are sorry for the omission of these two references which were not in our knowledge. In fact we derived these equations and Eq.(4) of Ref.[12] [J.D. Anderson and S.M. Grimes, Phys. Rev. C 41, 2904 (1990) [4]] of our paper [1] as follows. From partial wave analysis of scattering theory, we know the standard expressions for scattering σsc and reaction σr cross sections as

A COVARIANT APPROACH TO THE GENERALIZED MULTI-INFLATON COSMOLOGICAL PERTURBATION

Following the formalism developed in Astrophys. J.375, 443 (1991), differential equations for the gauge invariant scalar part of the metric perturbation in the Friedmann–Robertson–Walker background with multiple inflatons with arbitrary field metric are obtained without any specific choice of gauge. Subsequently, an algorithm for the solution of these equations in the slow-roll approximation is given without any prior choice of the basis system in the field manifold. Vector and tensor perturbations are also briefly reviewed.