22,945 research outputs found
Nonequilibrium Work distributions for a trapped Brownian particle in a time dependent magnetic field
We study the dynamics of a trapped, charged Brownian particle in presence of
a time dependent magnetic field. We calculate work distributions for different
time dependent protocols. In our problem thermodynamic work is related to
variation of vector potential with time as opposed to the earlier studies where
the work is related to time variation of the potentials which depends only on
the coordinates of the particle. Using Jarzynski identity and Crook's equality
we show that the free energy of the particle is independent of the magnetic
field, thus complementing the Bohr-van Leeuwen theorem. We also show that our
system exhibits a parametric resonance in certain parameter space.Comment: 4 pages and 5 figure
Entropy production theorems and some consequences
The total entropy production fluctuations are studied in some exactly
solvable models. For these systems, the detailed fluctuation theorem holds even
in the transient state, provided initially the system is prepared in thermal
equilibrium. The nature of entropy production during the relaxation of a system
to equilibrium is analyzed. The averaged entropy production over a finite time
interval gives a better bound for the average work performed on the system than
that obtained from the well known Jarzynski equality. Moreover, the average
entropy production as a quantifier for information theoretic nature of
irreversibility for finite time nonequilibrium processes is discussed.Comment: 12 pages, 3 figure
Nonlinear Spinor Fields and its role in Cosmology
Different characteristic of matter influencing the evolution of the Universe
has been simulated by means of a nonlinear spinor field. Exploiting the spinor
description of perfect fluid and dark energy evolution of the Universe given by
an anisotropic Bianchi type-VI, VI, V, III, I or isotropic
Friedmann-Robertson-Walker (FRW) one has been studied. It is shown that due to
some restrictions on metric functions, initial anisotropy in the models Bianchi
type-VI, VI, V and III does not die away, while the anisotropic Bianchi
type-I models evolves into the isotropic one.Comment: 22 pages, 12 Figure
Interacting spinor and scalar fields in Bianchi type-I Universe filled with viscous fluid: exact and numerical solutions
We consider a self-consistent system of spinor and scalar fields within the
framework of a Bianchi type I gravitational field filled with viscous fluid in
presence of a term. Exact self-consistent solutions to the
corresponding spinor, scalar and BI gravitational field equations are obtained
in terms of , where is the volume scale of BI universe. System of
equations for and \ve, where \ve is the energy of the viscous fluid,
is deduced. Some special cases allowing exact solutions are thoroughly studied.Comment: 18 pages, 6 figure
Role of c-axis pairs in V2O3 from the band-structure point of view
The common interpretation of the LDA band structure of VO is that
the apparent splitting of the band into a low intensity structure deep
below the Fermi energy and a high intensity feature above it, is due to the
bonding-antibonding coupling of the vertical V-V pair. Using tight-binding
fitting to --as well as first-principles NMTO downfolding of-- the spin-up
LDA+U band, we show that there are other hopping integrals which are
equally important for the band shape as the integral for hopping between the
partners of the pair
Optical properties of random alloys : Application to Cu_{50}Au_{50} and Ni_{50}Pt_{50}
In an earlier paper [K. K. Saha and A. Mookerjee, Phys. Rev. B 70 (2004) (in
press) or, cond-mat/0403456] we had presented a formulation for the calculation
of the configuration-averaged optical conductivity in random alloys. Our
formulation is based on the augmented-space theorem introduced by one of us [A.
Mookerjee, J. Phys. C: Solid State Phys. 6, 1340 (1973)]. In this communication
we shall combine our formulation with the tight-binding linear muffin-tin
orbitals (TB-LMTO) technique to study the optical conductivities of two alloys
Cu_{50}Au_{50} and Ni_{50}Pt_{50}.Comment: 5 pages, 7 figure
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