70,308 research outputs found
Comment on "Classical and Quantum Interaction of the Dipole"
In this paper I have presented Comment on Anandan's paper (J. Anandan, Phys.
Rev. Lett. 85, 1354 (2000)) [hep-th/9910018].Comment: 1 page, revtex; small changes, mainly typos, according to the
published version in Phys. Rev. Let
Comment on "R\"{o}ntgen Quantum Phase Shift: A Semiclassical Local Electrodynamical Effect?''
This paper is Comment on the paper: S.A.R. Horsley and M. Babiker, Phys. Rev.
Lett. 95, 010405 (2005).Comment: minor changes in the text, some references are changed, according to
the version which is accepted for publication in Phys. Rev. Let
Electric-Magnetic Duality and Topological Insulators
We work out the action of the SL(2,Z) electric-magnetic duality group for an
insulator with a non-trivial permittivity, permeability and theta-angle. This
theory has recently been proposed to be the correct low-energy effective action
for topological insulators. As applications, we give manifestly SL(2,Z)
covariant expressions for the Faraday rotation at orthogonal incidence at the
interface of two such materials, as well as for the induced magnetic and
electric charges, slightly clarifying the meaning of expressions previously
derived in the literature. We also use electric-magnetic duality to find a
gravitational dual for a strongly coupled version of this theory using the
AdS/CFT correspondence.Comment: 4 pages; version accepted by PR
Biot-Savart-like law in electrostatics
The Biot-Savart law is a well-known and powerful theoretical tool used to
calculate magnetic fields due to currents in magnetostatics. We extend the
range of applicability and the formal structure of the Biot-Savart law to
electrostatics by deriving a Biot-Savart-like law suitable for calculating
electric fields. We show that, under certain circumstances, the traditional
Dirichlet problem can be mapped onto a much simpler Biot-Savart-like problem.
We find an integral expression for the electric field due to an arbitrarily
shaped, planar region kept at a fixed electric potential, in an otherwise
grounded plane. As a by-product we present a very simple formula to compute the
field produced in the plane defined by such a region. We illustrate the
usefulness of our approach by calculating the electric field produced by planar
regions of a few nontrivial shapes.Comment: 14 pages, 6 figures, RevTex, accepted for publication in the European
Journal of Physic
The total nucleon-nucleon cross section at large N_c
It is shown that at sufficiently large for incident momenta which are
much larger than the QCD, the total nucleon-nucleon cross section is
independent of incident momentum and given by . This result is valid in the extreme large
regime of and has corrections of relative order . A possible connection of this result to the
Froissart-Martin bound is discussed.Comment: 4 page
A simple variational principle for classical spinning particle with anomalous magnetic momentum
We obtain Bargmann-Michel-Telegdi equations of motion of classical spinning
particle using Lagrangian variational principle with Grassmann variables.Comment: 3 pages, late
Towards a bulk theory of flexoelectricity
Flexoelectricity is the linear response of polarization to a strain gradient.
Here we address the simplest class of dielectrics, namely elemental cubic
crystals, and we prove that therein there is no extrinsic (i.e. surface)
contribution to flexoelectricity in the thermodynamic limit. The flexoelectric
tensor is expressed as a bulk response of the solid, manifestly independent of
surface configurations. Furthermore, we prove that the flexoelectric responses
induced by a long-wavelength phonon and by a uniform strain gradient are
identical.Comment: 5 pages, 1 figure (2 panels
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