10,159 research outputs found
Non-Abelian gauge fields in the gradient expansion: generalized Boltzmann and Eilenberger equations
We present a microscopic derivation of the generalized Boltzmann and
Eilenberger equations in the presence of non-Abelian gauges, for the case of a
non-relativistic disordered Fermi gas. A unified and symmetric treatment of the
charge and spin degrees of freedom is achieved. Within this
framework, just as the Lorentz force generates the Hall effect, so does
its counterpart give rise to the spin Hall effect. Considering elastic
and spin-independent disorder we obtain diffusion equations for charge and spin
densities and show how the interplay between an in-plane magnetic field and a
time dependent Rashba term generates in-plane charge currents.Comment: 11 pages, 1 figure; some corrections and updated/extended reference
Superconductivity-Related Insulating Behavior
We present the results of an experimental study of superconducting,
disordered, thin-films of amorphous Indium Oxide. These films can be driven
from the superconducting phase to a reentrant insulating state by the
application of a perpendicular magnetic field (). We find that the high-
insulator exhibits activated transport with a characteristic temperature,
. has a maximum value () that is close to the
superconducting transition temperature () at = 0, suggesting a
possible relation between the conduction mechanisms in the superconducting and
insulating phases. and display opposite dependences on the
disorder strength.Comment: Tex file and 5 figures; Revised version; To appear in Phys. Rev.
Lett. (2004
Mesoscopic Spin-Hall Effect in 2D electron systems with smooth boundaries
Spin-Hall effect in ballistic 2D electron gas with Rashba-type spin-orbit
coupling and smooth edge confinement is studied. We predict that the interplay
of semiclassical electron motion and quantum dynamics of spins leads to several
distinct features in spin density along the edge that originate from
accumulation of turning points from many classical trajectories. Strong peak is
found near a point of the vanishing of electron Fermi velocity in the lower
spin-split subband. It is followed by a strip of negative spin density that
extends until the crossing of the local Fermi energy with the degeneracy point
where the two spin subbands intersect. Beyond this crossing there is a wide
region of a smooth positive spin density. The total amount of spin accumulated
in each of these features exceeds greatly the net spin across the entire edge.
The features become more pronounced for shallower boundary potentials,
controlled by gating in typical experimental setups.Comment: 4 pages, 4 figures, published versio
Vlasov scaling for the Glauber dynamics in continuum
We consider Vlasov-type scaling for the Glauber dynamics in continuum with a
positive integrable potential, and construct rescaled and limiting evolutions
of correlation functions. Convergence to the limiting evolution for the
positive density system in infinite volume is shown. Chaos preservation
property of this evolution gives a possibility to derive a non-linear
Vlasov-type equation for the particle density of the limiting system.Comment: 32 page
Revision of the green lacewing subgenus Ankylopteryx (Sencera) (Neuroptera, Chrysopidae)
The Australasian and Oriental green lacewing subgenus Ankylopteryx (Sencera) Navás (Chrysopinae: Ankylopterygini) is examined and its diversity and placement among other members of the tribe Ankylopterygini is discussed. After study of specimens spanning the full distribution and anatomical range of variation for the subgenus, all prior putative species, resulting in the sole valid species are newly synonymized, Ankylopteryx (Sencera) anomala (Brauer). Accordingly, the following new synonymies are established: Sencera scioneura Navás, syn. n., Sencera feae Navás, syn. n., and Sencera exquisita Nakahara, syn. n. [all under the name Ankylopteryx (Sencera) anomala]. A lectotype is newly designated for Ankylopteryx (Sencera) anomala so as to stabilize the application of the name. To support our hypotheses, the wing and general body coloration as well as the male genitalia are reviewed. We elaborate on the possibility of Ankylopteryx (Sencera) anomala being nothing more than an autapomorphic species of Ankylopteryx Brauer, as it was originally described. The species is not sufficiently distinct to warrant recognition as a separate subgenus within the group, and most certainly not as its own genus as has been advocated by past authors. Nonetheless, we do not for now go so far as to synonymize the subgenus until a more extensive phylogenetic analysis is undertaken with multiple representative species from across Ankylopteryx and other ankylopterygine genera. Lastly, we comment on the biology of Ankylopteryx (Sencera) anomala in terms of the attraction of males to methyl eugenol and on the widespread practice of splitting within Chrysopidae
Revision of the green lacewing subgenus Ankylopteryx (Sencera) (Neuroptera, Chrysopidae)
The Australasian and Oriental green lacewing subgenus Ankylopteryx (Sencera) Navás (Chrysopinae: Ankylopterygini) is examined and its diversity and placement among other members of the tribe Ankylopterygini is discussed. After study of specimens spanning the full distribution and anatomical range of variation for the subgenus, all prior putative species, resulting in the sole valid species are newly synonymized, Ankylopteryx (Sencera) anomala (Brauer). Accordingly, the following new synonymies are established: Sencera scioneura Navás, syn. n., Sencera feae Navás, syn. n., and Sencera exquisita Nakahara, syn. n. [all under the name Ankylopteryx (Sencera) anomala]. A lectotype is newly designated for Ankylopteryx (Sencera) anomala so as to stabilize the application of the name. To support our hypotheses, the wing and general body coloration as well as the male genitalia are reviewed. We elaborate on the possibility of Ankylopteryx (Sencera) anomala being nothing more than an autapomorphic species of Ankylopteryx Brauer, as it was originally described. The species is not sufficiently distinct to warrant recognition as a separate subgenus within the group, and most certainly not as its own genus as has been advocated by past authors. Nonetheless, we do not for now go so far as to synonymize the subgenus until a more extensive phylogenetic analysis is undertaken with multiple representative species from across Ankylopteryx and other ankylopterygine genera. Lastly, we comment on the biology of Ankylopteryx (Sencera) anomala in terms of the attraction of males to methyl eugenol and on the widespread practice of splitting within Chrysopidae
Shape of primary proton spectrum in multi-TeV region from data on vertical muon flux
It is shown, that primary proton spectrum, reconstructed from sea-level and
underground data on muon spectrum with the use of QGSJET 01, QGSJET II, NEXUS
3.97 and SIBYLL 2.1 interaction models, demonstrates not only model-dependent
intensity, but also model-dependent form. For correct reproduction of muon
spectrum shape primary proton flux should have non-constant power index for all
considered models, except SIBYLL 2.1, with break at energies around 10-15 TeV
and value of exponent before break close to that obtained in ATIC-2 experiment.
To validate presence of this break understanding of inclusive spectra behavior
in fragmentation region in p-air collisions should be improved, but we show,
that it is impossible to do on the basis of the existing experimental data on
primary nuclei, atmospheric muon and hadron fluxes.Comment: Submitted to Phys. Rev.
Out-of-plane spin polarization from in-plane electric and magnetic fields
We show that the joint effect of spin-orbit and magnetic fields leads to a
spin polarization perpendicular to the plane of a two-dimensional electron
system with Rashba spin-orbit coupling and in-plane parallel dc magnetic and
electric fields, for angle-dependent impurity scattering or nonparabolic energy
spectrum, while only in-plane polarization persists for simplified models. We
derive Bloch equations, describing the main features of recent experiments,
including the magnetic field dependence of static and dynamic responses.Comment: 5 pages and 1 figure in main text, 5 pages in appendi
Drop Splashing on a Dry Smooth Surface
The corona splash due to the impact of a liquid drop on a smooth dry
substrate is investigated with high speed photography. A striking phenomenon is
observed: splashing can be completely suppressed by decreasing the pressure of
the surrounding gas. The threshold pressure where a splash first occurs is
measured as a function of the impact velocity and found to scale with the
molecular weight of the gas and the viscosity of the liquid. Both experimental
scaling relations support a model in which compressible effects in the gas are
responsible for splashing in liquid solid impacts.Comment: 11 pages, 4 figure
Tunneling currents in ferromagnetic systems with multiple broken symmetries
SHORTENED ABSTRACT: A system exhibiting multiple simultaneously broken
symmetries offers the opportunity to influence physical phenomena such as
tunneling currents by means of external control parameters. In this paper, we
consider the broken SU(2) (internal spin) symmetry of ferromagnetic systems
coexisting with \textit{i)} the broken U(1) symmetry of superconductors and
\textit{ii)} the broken spatial inversion symmetry induced by a Rashba term in
a spin-orbit coupling Hamiltonian. In order to study the effect of these broken
symmetries, we consider tunneling currents that arise in two different systems;
tunneling junctions consisting of non-unitary spin-triplet ferromagnetic
superconductors and junctions consisting of ferromagnets with spin-orbit
coupling.Comment: Accepted for publication in Phys. Rev.
- …