4,160 research outputs found
Nonadiabatic charge pumping across two superconductors connected through a normal metal region by periodically driven potentials
Periodically driven systems exhibit resonance when the difference between an
excited state energy and the ground state energy is an integer multiple of
times the driving frequency. On the other hand, when a superconducting
phase difference is maintained between two superconductors, subgap states
appear which carry a Josephson current. A driven Josephson junction therefore
opens up an interesting avenue where the excitations due to applied driving
affect the current flowing from one superconductor to the other. Motivated by
this, we study charge transport in a superconductor-normal metal-superconductor
(SNS) junction where oscillating potentials are applied to the normal metal
region. We find that for small amplitudes of the oscillating potential, driving
at one site reverses the direction of current at the superconducting phase
differences when difference between the subgap eigenenergies of the undriven
Hamiltonian is integer multiple of times the driving frequency. For
larger amplitudes of oscillating potential, driving at one site exhibits richer
features. We show that even when the two superconductors are maintained at same
superconducting phase, a current can be driven by applying oscillating
potentials to two sites in the normal metal differing by a phase. We find that
when there is a nonzero Josephson current in the undriven system, the local
peaks and valleys in current of the system driven with an amplitude of
oscillating potential smaller than the superconducting gap indicates sharp
excitations in the system. In the adiabatic limit, we find that charge
transferred in one time period diverges as a powerlaw with pumping frequency
when a Josephson current flows in the undriven system. Our calculations are
exact and can be applied to finite systems. We discuss possible experimental
setups where our predictions can be tested.Comment: 9 pages, 9 figures. Published versio
On the -algebra in the Calegero-Sutherland model using the Exchange operators
We study the algebra in the Calegero-Sutherland model using the
exchange operators. The presence of all the sub-algebras of is shown
in this model. A simplified proof for this algebra, in the symmetric ordered
basics, is given. It is pointed out that the algebra contains in general,
nonlinear terms. Possible connection to the nonlinear is discussed.Comment: Plain Tex, no figures, 13 page
Consistent Non-Minimal Couplings of Massive Higher-Spin Particles
The mutual compatibility of the dynamical equations and constraints
describing a massive particle of arbitrary spin, though essential for
consistency, is generically lost in the presence of interactions. The
conventional Lagrangian approach avoids this difficulty, but fails to ensure
light-cone propagation and becomes very cumbersome. In this paper, we take an
alternative route--the involutive form of the equations and constraints--to
guarantee their algebraic consistency. This approach enormously simplifies the
search for consistent interactions, now seen as deformations of the involutive
system, by keeping manifest the causal propagation of the correct number of
degrees of freedom. We consider massive particles of arbitrary integer spin in
electromagnetic and gravitational backgrounds to find their possible
non-minimal local couplings. Apart from easily reproducing some well-known
results, we find restrictions on the backgrounds for consistent propagation of
such a particle in isolation. The results can be altered by non-local
interactions that may arise from additional massive states in the interacting
theory.Comment: 26 pages; to appear in Nuclear Physics B; analyses of consistent
backgrounds improve
Hamiltonian vs Lagrangian Embedding of a Massive Spin-one Theory Involving 2-form Field
We consider the Hamiltonian and Lagrangian embedding of a first-order,
massive spin-one, gauge non-invariant theory involving anti-symmetric tensor
field. We apply the BFV-BRST generalised canonical approach to convert the
model to a first class system and construct nil-potent BFV-BRST charge and an
unitarising Hamiltonian. The canonical analysis of the St\"uckelberg
formulation of this model is presented. We bring out the contrasting feature in
the constraint structure, specifically with respect to the reducibility aspect,
of the Hamiltonian and the Lagrangian embedded model. We show that to obtain
manifestly covariant St\"uckelberg Lagrangian from the BFV embedded
Hamiltonian, phase space has to be further enlarged and show how the reducible
gauge structure emerges in the embedded model.Comment: Revtex, 13 pages, no figure, to appear in Int. J. Mod. Phys.
Women empowerment and micro finance : Case study from Kerala
The subject of micro-finance is considered as significant and emerging trend in the present scenario for the empowerment of women. Micro finance programmes are promoted as an important strategy for women’s empowerment. Micro finance builds mutual trust and confidence between bankers and rural poor to encourage banking in a segment of population where formal financial institutions usually find difficult to reach. The present paper examines the economic impact of micro finance beneficiaries and whether the economic empowerment has resulted in the generation of a set of self reliant women. The Thiruvananthapuram district of Kerala State was selected for the case study. The survey shows about the positive impact of the development programme of Kudumbashree, a micro financial institution in Kerala, India.women empowerment micro finance poverty.
The Hydrodynamical Limit of Quantum Hall system
We study the current algebra of FQHE systems in the hydrodynamical limit of
small amplitude, long-wavelength fluctuations. We show that the algebra
simplifies considerably in this limit. The hamiltonian is expressed in a
current-current form and the operators creating inter-Landau level and lowest
Landau level collective excitations are identified.Comment: Revtex, 16 page
Aspects of Noncommutative Scalar/Tensor Duality
We study the noncommutative massless Kalb-Ramond gauge field coupled to a
dynamical U(1) gauge field in the adjoint representation together with a
compensating vector field. We derive the Seiberg-Witten map and obtain the
corresponding mapped action to first order in . The (emergent) gravity
structure found in other situations is not present here. The off-shell dual
scalar theory is derived and it does not coincide with the Seiberg-Witten
mapped scalar theory. Dispersion relations are also discussed. The p-form
generalization of the Seiberg-Witten map to order is also derived.Comment: 7 pages, typos corrected, a footnote removed and a sentence added in
the tex
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