36,313 research outputs found
Transmission coefficient and two-fold degenerate discrete spectrum of spin-1 bosons in a double-step potential
The scattering of spin-1 bosons in a nonminimal vector double-step potential
is described in terms of eigenstates of the helicity operator and it is shown
that the transmission coefficient is insensitive to the choice of the
polarization of the incident beam. Poles of the transmission amplitude reveal
the existence of a two-fold degenerate spectrum. The results are interpreted in
terms of solutions of two coupled effective Schr\"{o}dinger equations for a
finite square well with additional -functions situated at the borders.Comment: arXiv admin note: substantial text overlap with arXiv:1203.119
New solutions of the D-dimensional Klein-Gordon equation via mapping onto the nonrelativistic one-dimensional Morse potential
New exact analytical bound-state solutions of the D-dimensional Klein-Gordon
equation for a large set of couplings and potential functions are obtained via
mapping onto the nonrelativistic bound-state solutions of the one-dimensional
generalized Morse potential. The eigenfunctions are expressed in terms of
generalized Laguerre polynomials, and the eigenenergies are expressed in terms
of solutions of irrational equations at the worst. Several analytical results
found in the literature, including the so-called Klein-Gordon oscillator, are
obtained as particular cases of this unified approac
Street Flowers: Urban Survivors of the Privileged Land Conference Paper
I have presented papers about Street Flowers: Urban Survivors of the Privileged Land at 'Duration’ - an international, interdisciplinary conference exploring the temporality of contemporary public arts practice
Brownian motion meets Riemann curvature
The general covariance of the diffusion equation is exploited in order to
explore the curvature effects appearing on brownian motion over a d-dimensional
curved manifold. We use the local frame defined by the so called Riemann normal
coordinates to derive a general formula for the mean-square geodesic distance
(MSD) at the short-time regime. This formula is written in terms of
invariants that depend on the Riemann curvature tensor. We study the
n-dimensional sphere case to validate these results. We also show that the
diffusion for positive constant curvature is slower than the diffusion in a
plane space, while the diffusion for negative constant curvature turns out to
be faster. Finally the two-dimensional case is emphasized, as it is relevant
for the single particle diffusion on biomembranes.Comment: 16 pages and 3 figure
Higher particle form factors of branch point twist fields in integrable quantum field theories
In this paper we compute higher particle form factors of branch point twist
fields. These fields were first described in the context of massive
1+1-dimensional integrable quantum field theories and their correlation
functions are related to the bi-partite entanglement entropy. We find analytic
expressions for some form factors and check those expressions for consistency,
mainly by evaluating the conformal dimension of the corresponding twist field
in the underlying conformal field theory. We find that solutions to the form
factor equations are not unique so that various techniques need to be used to
identify those corresponding to the branch point twist field we are interested
in. The models for which we carry out our study are characterized by staircase
patterns of various physical quantities as functions of the energy scale. As
the latter is varied, the beta-function associated to these theories comes
close to vanishing at several points between the deep infrared and deep
ultraviolet regimes. In other words, renormalisation group flows approach the
vicinity of various critical points before ultimately reaching the ultraviolet
fixed point. This feature provides an optimal way of checking the consistency
of higher particle form factor solutions, as the changes on the conformal
dimension of the twist field at various energy scales can only be accounted for
by considering higher particle form factor contributions to the expansion of
certain correlation functions.Comment: 25 pages, 4 figures; v2 contains small correction
Sum Rules for the Optical and Hall Conductivity in Graphene
Graphene has two atoms per unit cell with quasiparticles exhibiting the
Dirac-like behavior. These properties lead to interband in addition to
intraband optical transitions and modify the -sum rule on the longitudinal
conductivity. The expected dependence of the corresponding spectral weight on
the applied gate voltage in a field effect graphene transistor is . For , its temperature dependence is rather
than the usual . For the Hall conductivity, the corresponding spectral
weight is determined by the Hall frequency which is linear in the
carrier imbalance density , and hence proportional to , and is
different from the cyclotron frequency for Dirac quasiparticles.Comment: 16 pages, RevTeX4, 4 EPS figures; v2: to match PRB versio
Interplay of Wiener-Hopf and Hankel operators with almost periodic Fourier symbols on standard and variable exponent Lebesgue spaces
Wiener-Hopf plus Hankel and Wiener-Hopf minus Hankel operators in both frameworks of standard and variable exponent Lebesgue spaces are considered in this paper. The main aim is to describe certain dependencies between the Fredholm property of some Wiener-Hopf operators acting between variable exponent Lebesgue spaces and the invertibility of Wiener-Hopf plus and minus Hankel operators on all the standard Lebesgue spaces. Different types of Fourier symbols will be used but special focus will be considered on the Wiener subclass of almost periodic matrix functions. In the first part of the paper we will give a survey of investigations on related results. This will be useful at the end of the paper to derive the above mentioned dependencies between the operators under study
Impurity induced spin-orbit coupling in graphene
We study the effect of impurities in inducing spin-orbit coupling in
graphene. We show that the sp3 distortion induced by an impurity can lead to a
large increase in the spin-orbit coupling with a value comparable to the one
found in diamond and other zinc-blende semiconductors. The spin-flip scattering
produced by the impurity leads to spin scattering lengths of the order found in
recent experiments. Our results indicate that the spin-orbit coupling can be
controlled via the impurity coverage.Comment: 4 pages, 6 figure
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