Action-at-a-distance electrodynamics in Quasi-steady-state cosmology

Action-at-a-distance electrodynamics - alternative approach to field theory - can be extended to cosmological models using conformal symmetry. An advantage of this is that the origin of arrow of time in electromagnetism can be attributed to the cosmological structure. Different cosmological models can be investigated, based on Wheeler-Feynman absorber theory, and only those models can be considered viable for our universe which have net full retarded electromagnetic interactions i.e. forward direction of time. This work evaluates quasi-steady-state model and demonstrates that it admits full retarded and not advanced solution. Thus QSSC satisfies this necessary condition for a correct cosmological model, based on action-at-a-distance formulation.Comment: Section 4 added with supplementary calculation; 8 pages; 1 figure; Communicated by Prof. J. V. Narlikar (IUCAA, Pune, India); Submitted to Pramana (Journal of Physics published by Indian Academy of Sciences) on Sep 4, 201

Effect of pressure on the electronic and magnetic properties of CdV2_2O4_4: Density functional theory studies

We investigate the effect of pressure on the electronic and magnetic states of CdV$_2$O$_4$ by using ab initio electronic structure calculations. The Coulomb correlation and spin-orbit coupling play important role in deciding the structural, electronic and magnetic properties of the compound. The total magnetic moment of V ion is found to be $\sim$1.3 $\mu_B$ and making an angle of $\sim$9.5 degree with the z-axis. In the tetragonal phase, the ground state is the orbital ordered state where V $d_{xz}$ and $d_{yz}$ obtitals are mainly occupied at the neighbouring sites. This work predicts the electronic phase transition from orbital-ordered-insulator to orbital-ordered-metal to orbital-disordered-metal with increasing pressure. The pressure induced broadening of lower and upper Hubbard bands gives rise to metal-insulator transition above 35 GPa. The simple mean-field theory used in the present work is able to describe the pressure dependent variation of the antiferromagnetic transition temperature suggesting the applicability of the method in the study of the magnetic behaviour of similar geometrically frustrated systems.Comment: 12 pages, 7 figures, to appear in Phys. Rev.