19,092 research outputs found
Electric and Magnetic fields due to Dirac particles in FRW spacetime
Some solutions of the Maxwell equations with Dirac particles for the source
in FRW spacetime are discussed. The Green's function of the equation for the
radial component of the Maxwell fields, F_{r\eta} and F_{\theta\phi} is solved.
Green's function is found to reduce to that of Minkowskian spacetime in the
appropriate limit. Also, the Lienard-Wiechert type solution is derived. Also,
the solutions with the Dirac particle current is also presented. It is found
that the F_{r\eta} is composed of even angular momentum states while the odd
states constitue F_{\theta\phi} .Comment: 8 pages including 2 figure
Spectral density and metal-insulator phase transition in Mott insulators within RDMFT
We present a method for calculating the spectrum of periodic solids within
reduced density matrix functional theory. This method is validated by a
detailed comparison of the angular momentum projected spectral density with
that of well established many-body techniques, in all cases finding an
excellent agreement. The physics behind the pressure induced insulator-metal
phase transition in MnO is investigated. The driving mechanism of this
transition is identified as increased crystal field splitting with pressure,
resulting in a charge redistribution between the Mn and symmetry
projected states.Comment: arXiv admin note: text overlap with arXiv:0912.111
Reduced Density Matrix Functional for Many-Electron Systems
Reduced density matrix functional theory for the case of solids is presented
and a new exchange correlation functional based on a fractional power of the
density matrix is introduced. We show that compared to other functionals, this
produces more accurate results for both finite systems. Moreover, it captures
the correct band gap behavior for conventional semiconductors as well as
strongly correlated Mott insulators, where a gap is obtained in absence of any
magnetic ordering.Comment: 4 figs and 1 tabl
Orbital currents in the Colle-Salvetti correlation energy functional and the degeneracy problem
Popular density functionals for the exchange-correlation energy typically
fail to reproduce the degeneracy of different ground states of open-shell
atoms. As a remedy, functionals which explicitly depend on the current density
have been suggested. We present an analysis of this problem by investigating
functionals that explicitly depend on the Kohn-Sham orbitals. Going beyond the
exact-exchange approximation by adding correlation in the form of the
Colle-Salvetti functional we show how current-dependent terms enter the
Colle-Salvetti expression and their relevance is evaluated. A very good
description of the degeneracy of ground-states for atoms of the first and
second row of the periodic table is obtained
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