14,522 research outputs found
Lower Bound for the Fermi Level Density of States of a Disordered D-Wave Superconductor in Two Dimensions
We consider a disordered d--wave superconductor in two dimensions. Recently,
we have shown in an exact calculation that for a lattice model with a
Lorentzian distributed random chemical potential the quasiparticle density of
states at the Fermi level is nonzero. As the exact result holds only for the
special choice of the Lorentzian, we employ different methods to show that for
a large class of distributions, including the Gaussian distribution, one can
establish a nonzero lower bound for the Fermi level density of states. The fact
that the tails of the distributions are unimportant in deriving the lower bound
shows that the exact result obtained before is generic.Comment: 15 preprint pages, no figures, submitted to PR
TOPO-EUROPE: Coupled Deep Earth - Surface Processes in Europe
TOPO-EUROPE is a multidisciplinary international research program that addresses the interaction of processes inherent to the deep Earth (lithosphere, mantle) with surface processes (erosion, climate, sea level), which together shaped the topography of Europe. The objective of the TOPO-EUROPE project is to assess neotectonic deformation rates and to quantify related geo-risks, such as earthquakes, flooding, landslides, rock falls and volcanism. Research, incorporating iterative data interactive modelling, focuses on the lithosphere memory and neotectonics, with special attention on the thermo-mechanical structure of the lithosphere, mechanisms controlling large-scale plate boundary and intraplate deformations, anomalous subsidence and uplift, and links with surface processes and topography evolution. The TOPO-EUROPE natural laboratories, in which these processes are analysed, cover a wide range of geodynamic settings. These include the post-collisional Alpine/Carpathian/Pannonian-Basin system, the very active Aegean-Anatolian and Apennines-Tyrrhenian orogens and back-arc basins, the Caucasus-Levant area in the Arabia-Europe collision zone, the Iberian Peninsula caught up between Alpine orogens, the meta-stable West and Central European Platform, the stable East-European Platform and the seismically active and elevated Scandinavian continental margin. The TOPO-EUROPE project is a component of the International Lithosphere Program and was initiated with the support of Academia Europaea. A European Science Foundation EUROCORES project provides funding for part of the TOPO-EUROPE research. Other parts of TOPO-EUROPE require support by participating organization
Very high energy emission from the hard spectrum sources HESS J1641-463, HESS J1741-302 and HESS J1826-130
A recent study of the diffuse -ray emission in the Central Molecular
Zone using very high energy (VHE, E 0.1 TeV) H.E.S.S. data suggests that
the Galactic Center (GC) is the most plausible supplier of Galactic
ultra-relativistic cosmic-rays (CRs) up to the knee at about 10 eV
(PeV). However, the GC might not be the only source capable to accelerate CRs
up to PeV energies in the Galaxy. Here we present H.E.S.S. data analysis
results and interpretation of three H.E.S.S. sources, with spectra extending
beyond 10 TeV and relatively hard spectral indices compared with the average
spectral index of H.E.S.S. sources, namely HESS J1641-463, HESS J1741-302 and
HESS J1826-130. Although the nature of these VHE -ray sources is still
open, their spectra suggest that the astrophysical objects producing such
emission must be capable of accelerating the parental particle population up to
energies of at least several hundreds of TeV. Assuming a hadronic scenario,
dense gas regions can provide rich target material for accelerated particles to
produce VHE -ray emission via proton-proton interactions followed by a
subsequent decay. Thus, detailed investigations of the interstellar
medium along the line of sight to all of these sources have been performed by
using data from available atomic and molecular hydrogen surveys. The results
point out the existence of dense interstellar gas structures coincident with
the best fit positions of these sources. One can find possible hadronic models
with CRs being accelerated close to the PeV energies to explain the
-ray emission from all of these sources, which opens up the possibility
that a population of PeV CR accelerators might be active in the Galaxy.Comment: 8 pages, 2 figures, in Proceedings of 35th ICRC, Busan (Korea) 201
¿Conflictos en la integración regional? Consideraciones acerca de la superposición de los acuerdos internacionales de inversión, los acuerdos comerciales regionales y la OMC
La creciente interdependencia económica internacional resultó en el desarrollo de diversas organizaciones y acuerdos regionales como los acuerdos comerciales regionales, los acuerdos internacionales de inversión y la Organización Mundial de Comercio (omc). En el panorama actual, diversos países son miembros de estos acuerdos y organizaciones concomitantemente. El gran incremento de los resultados de soluciones de diferencias debido al éxito del Entendimiento sobre Solución de Diferencias (esd) de la omc y el crecimiento paralelo del uso de las provisiones de los aii sobre solución de diferencias entre Estados e inversores llevaron a afirmaciones sobre el distanciamiento del derecho internacional de las inversiones y el derecho internacional comercial, lo que podría generar problemas con relación a la coherencia y estabilidad del derecho económico
A new electromagnetic mode in graphene
A new, weakly damped, {\em transverse} electromagnetic mode is predicted in
graphene. The mode frequency lies in the window
, where is the chemical potential, and can be
tuned from radiowaves to the infrared by changing the density of charge
carriers through a gate voltage.Comment: 5 pages, 4 figure
HESS J1826130: A Very Hard -Ray Spectrum Source in the Galactic Plane
HESS J1826130 is an unidentified hard spectrum source discovered by
H.E.S.S. along the Galactic plane, the spectral index being = 1.6 with
an exponential cut-off at about 12 TeV. While the source does not have a clear
counterpart at longer wavelengths, the very hard spectrum emission at TeV
energies implies that electrons or protons accelerated up to several hundreds
of TeV are responsible for the emission. In the hadronic case, the VHE emission
can be produced by runaway cosmic-rays colliding with the dense molecular
clouds spatially coincident with the H.E.S.S. source.Comment: 6 pages, 3 figures, Proceedings of the 6th International Symposium on
High Energy Gamma-Ray Astronomy (Gamma2016), Heidelberg, German
Nonlinear electromagnetic response of graphene: Frequency multiplication and the self-consistent-field effects
Graphene is a recently discovered carbon based material with unique physical
properties. This is a monolayer of graphite, and the two-dimensional electrons
and holes in it are described by the effective Dirac equation with a vanishing
effective mass. As a consequence, electromagnetic response of graphene is
predicted to be strongly non-linear. We develop a quasi-classical kinetic
theory of the non-linear electromagnetic response of graphene, taking into
account the self-consistent-field effects. Response of the system to both
harmonic and pulse excitation is considered. The frequency multiplication
effect, resulting from the non-linearity of the electromagnetic response, is
studied under realistic experimental conditions. The frequency up-conversion
efficiency is analysed as a function of the applied electric field and
parameters of the samples. Possible applications of graphene in terahertz
electronics are discussed.Comment: 14 pages, 7 figures, invited paper written for a special issue of
JPCM "Terahertz emitters
Scaling near random criticality in two-dimensional Dirac fermions
Recently the existence of a random critical line in two dimensional Dirac
fermions is confirmed. In this paper, we focus on its scaling properties,
especially in the critical region. We treat Dirac fermions in two dimensions
with two types of randomness, a random site (RS) model and a random hopping
(RH) model. The RS model belongs to the usual orthogonal class and all states
are localized. For the RH model, there is an additional symmetry expressed by
. Therefore, although all non-zero energy states
localize, the localization length diverges at the zero energy. In the weak
localization region, the generalized Ohm's law in fractional dimensions,
, has been observed for the RH model.Comment: RevTeX with 4 postscript figures, To appear in Physical Review
Conductivity in Two-Dimensional Disordered Model with Anisotropic Long-Range Hopping
We consider two-dimensional system of particles localized on randomly
distributed sites of squared lattice with anisotropic transfer matrix elements
between localized sites. By summing of "diffusion ladder" and "cooperon ladder"
type vertices we calculated the conductivity for various sites and particles
densities.Comment: Latex, 10 page
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