2,390 research outputs found
Extreme nonlinear electrodynamics in metamaterials with very small linear dielectric permittivity
We consider a sub-wavelength periodic layered medium whose slabs are filled
by arbitrary linear metamaterials and standard nonlinear Kerr media and we show
that the homogenized medium behaves as a Kerr medium whose parameters can
assume values not available in standard materials. Exploiting such a parameter
availability, we focus on the situation where the linear relative dielectric
permittivity is very small thus allowing the observation of the extreme
nonlinear regime where the nonlinear polarization is comparable with or even
greater than the linear part of the overall dielectric response. The behavior
of the electromagnetic field in the extreme nonlinear regime is very peculiar
and characterized by novel features as, for example, the transverse power flow
reversing. In order to probe the novel regime, we consider a class of fields
(transverse magnetic nonlinear guided waves) admitting full analytical
description and we show that these waves are allowed to propagate even in media
with since the nonlinear polarization produces a
positive overall effective permittivity. The considered nonlinear waves
exhibit, in addition to the mentioned features, a number of interesting
properties like hyper-focusing induced by the phase difference between the
field components.Comment: 12 pages, 7 figure
Large Rapidity Gap Processes in Proton-Nucleus Collisions
The cross sections for a variety of channels of proton-nucleus interaction
associated with large gaps in rapidity are calculated within the Glauber-Gribov
theory. We found inelastic shadowing corrections to be dramatically enhanced
for such events. We employ the light-cone dipole formalism which allows to
calculate the inelastic corrections to all orders of the multiple interaction.
Although Gribov corrections are known to make nuclear matter more transparent,
we demonstrate that in some instances they lead to an opaqueness. Numerical
calculations are performed for the energies of the HERA-B experiment, and the
RHIC-LHC colliders.Comment: 19 page
Transparent Nuclei and Deuteron-Gold Collisions at RHIC
The current normalization of the cross section of inclusive high-pT particle
production in deuteron-gold collisions measured RHIC relies on Glauber
calculations for the inelastic d-Au cross section. These calculations should be
corrected for diffraction. Moreover, they miss the Gribov's inelastic shadowing
which makes nuclei more transparent (color transparency). The magnitude of this
effect rises with energy and it may dramatically affect the normalization of
the RHIC data. We evaluate these corrections employing the light-cone dipole
formalism and found a rather modest corrections for the current normalization
of the d-Au data. The results of experiments insensitive to diffraction
(PHENIX, PHOBOS) should be renormalized by about 20% down, while those which
include diffraction (STAR), by only 10%. Such a correction completely
eliminates the Cronin enhancement in the PHENIX data for pions. The largest
theoretical uncertainty comes from the part of the inelastic shadowing which is
related to diffractive gluon radiation, or gluon shadowing. Our estimate is
adjusted to data for the triple-Pomeron coupling, however, other models do not
have such a restrictions and predict much stronger gluon shadowing. Therefore,
the current data for high-pT hadron production in d-Au collisions at RHIC
cannot exclude in a model independent way the possibility if initial state
suppression proposed by Kharzeev-Levin-McLerran. Probably the only way to
settle this uncertainty is a direct measurement of the inelastic d-Au cross
sections at RHIC. Also d-Au collisions with a tagged spectator nucleon may
serve as a sensitive probe for nuclear transparency and inelastic shadowing. We
found an illuminating quantum-mechanical effect: the nucleus acts like a lens
focusing spectators into a very narrow cone.Comment: Latex 50 pages. Based on lectures given by the author at Workshop on
High-pT Correlations at RHIC, Columbia University, May-June, 2003. The
version to appear in PR
Dynamical Casimir-Polder interaction between an atom and surface plasmons
We investigate the time-dependent Casimir-Polder potential of a polarizable
two-level atom placed near a surface of arbitrary material, after a sudden
change in the parameters of the system. Different initial conditions are taken
into account. For an initially bare ground-state atom, the time-dependent
Casimir-Polder energy reveals how the atom is "being dressed" by virtual,
matter-assisted photons. We also study the transient behavior of the
Casimir-Polder interaction between the atom and the surface starting from a
partially dressed state, after an externally induced change in the atomic level
structure or transition dipoles. The Heisenberg equations are solved through an
iterative technique for both atomic and field operators in the medium-assisted
electromagnetic field quantization scheme. We analyze in particular how the
time evolution of the interaction energy depends on the optical properties of
the surface, in particular on the dispersion relationof surface plasmon
polaritons. The physical significance and the limits of validity of the
obtained results are discussed in detail.Comment: 12 pages, 8 figure
Winding Numbers, Complex Currents, and Non-Hermitian Localization
The nature of extended states in disordered tight binding models with a
constant imaginary vector potential is explored. Such models, relevant to
vortex physics in superconductors and to population biology, exhibit a
delocalization transition and a band of extended states even for a one
dimensional ring. Using an analysis of eigenvalue trajectories in the complex
plane, we demonstrate that each delocalized state is characterized by an
(integer) winding number, and evaluate the associated complex current. Winding
numbers in higher dimensions are also discussed.Comment: 4 pages, 2 figure
Universal eigenvector statistics in a quantum scattering ensemble
We calculate eigenvector statistics in an ensemble of non-Hermitian matrices
describing open quantum systems [F. Haake et al., Z. Phys. B 88, 359 (1992)] in
the limit of large matrix size. We show that ensemble-averaged eigenvector
correlations corresponding to eigenvalues in the center of the support of the
density of states in the complex plane are described by an expression recently
derived for Ginibre's ensemble of random non-Hermitian matrices.Comment: 4 pages, 5 figure
CP violation in unpolarized e^+ e^- to charginos at one loop level
We study CP violation in e^+ e^- to \tilde\chi_i^+\tilde\chi_j^- in the
framework of the MSSM. Though the cross section of this process is CP-even at
the tree level even for polarized electron-positron beams, we show that it
contains a CP-odd part at the one loop order and there are CP-odd observables
that can in principle be measured even using unpolarized electron-positron
beams. The relevant diagram calculations are briefly discussed and the results
of selected (box) diagram computations are shown.Comment: similar to Phys. Rev. D version, but corrected figs. 4, 5, 6 (factor
four
Microcantilever Studies of Angular Field Dependence of Vortex Dynamics in BSCCO
Using a nanogram-sized single crystal of BSCCO attached to a microcantilever
we demonstrate in a direct way that in magnetic fields nearly parallel to the
{\it ab} plane the magnetic field penetrates the sample in the form of
Josephson vortices rather than in the form of a tilted vortex lattice. We
further investigate the relation between the Josephson vortices and the pancake
vortices generated by the perpendicular field component.Comment: 5 pages, 8 figure
Eigenvector statistics in non-Hermitian random matrix ensembles
We study statistical properties of the eigenvectors of non-Hermitian random
matrices, concentrating on Ginibre's complex Gaussian ensemble, in which the
real and imaginary parts of each element of an N x N matrix, J, are independent
random variables. Calculating ensemble averages based on the quantity , where and are left and right eigenvectors of J, we show for large N that
eigenvectors associated with a pair of eigenvalues are highly correlated if the
two eigenvalues lie close in the complex plane. We examine consequences of
these correlations that are likely to be important in physical applications.Comment: 4 pages, no figure
Long range neutrino forces in the cosmic relic neutrino background
Neutrinos mediate long range forces among macroscopic bodies in vacuum. When
the bodies are placed in the neutrino cosmic background, these forces are
modified. Indeed, at distances long compared to the scale , the relic
neutrinos completely screen off the 2-neutrino exchange force, whereas for
small distances the interaction remains unaffected.Comment: 8 pages, 2 figure
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