4,838 research outputs found
Chiral Topological Superconductors Enhanced by Long-Range Interactions
We study the phase diagram and edge states of a two-dimensional p-wave
superconductor with long-range hopping and pairing amplitudes. New topological
phases and quasiparticles different from the usual short-range model are
obtained. When both hopping and pairing terms decay with the same exponent, one
of the topological chiral phases with propagating Majorana edge states gets
significantly enhanced by long-range couplings. On the other hand, when the
long-range pairing amplitude decays more slowly than the hopping, we discover
new topological phases where propagating Majorana fermions at each edge pair
nonlocally and become gapped even in the thermodynamic limit. Remarkably, these
nonlocal edge states are still robust, remain separated from the bulk, and are
localized at both edges at the same time. The inclusion of long-range effects
is potentially applicable to recent experiments with magnetic impurities and
islands in 2D superconductors.Comment: 5 pages, 3 figures. Close to published versio
The Jammed Phase of the Biham-Middleton-Levine Traffic Model
Initially a car is placed with probability p at each site of the
two-dimensional integer lattice. Each car is equally likely to be East-facing
or North-facing, and different sites receive independent assignments. At odd
time steps, each North-facing car moves one unit North if there is a vacant
site for it to move into. At even time steps, East-facing cars move East in the
same way. We prove that when p is sufficiently close to 1 traffic is jammed, in
the sense that no car moves infinitely many times. The result extends to
several variant settings, including a model with cars moving at random times,
and higher dimensions.Comment: 15 pages, 5 figures; revised journal versio
State-Uncertainty preferences and the Risk Premium in the Exchange rate market
This paper introduces state-uncertainty preferences into the Lucas (1982) economy, showing that this type of preferences helps to explain the exchange rate risk premium. Under these preferences we can distinguish between two factors driving the exchange rate risk premium: “macroeconomic risk” and “the risk associated with variation in the private agents’ perception on the level of uncertainty”. State-uncertainty preferences amount to assuming that a given level of consumption will yield a higher level of utility the lower is the level of uncertainty perceived by consumers. Furthermore, empirical evidence from three main European economies in the transition period to the euro provides empirical support for the modelForecasting, subspace methods, combining forecasts.
Thermodynamic aproach to particle size distribution in granular media
The study of particulate systems is of great interest in many fields of science and technology. Soil, sediments, powders, granular materials, colloidal and particulate
suspensions are examples of systems involving many size particles. For those systems, the statistical description of the particle size distribution (PSD), that is, the
mathematical distribution that defines the relative amounts of particles present, sorted according to size, is a crutial issue. The PSD can be important in understanding soil hydraulic properties, the geological origin or
sediments or the physical and chemical properties of granular materials and ceramics, among others
Localization and oscillations of Majorana fermions in a two-dimensional electron gas coupled with -wave superconductors
We study the localization and oscillation properties of the Majorana fermions
that arise in a two-dimensional electron gas (2DEG) with spin-orbit coupling
(SOC) and a Zeeman field coupled with a d-wave superconductor. Despite the
angular dependence of the d-wave pairing, localization and oscillation
properties are found to be similar to the ones seen in conventional s-wave
superconductors. In addition, we study a microscopic lattice version of the
previous system that can be characterized by a topological invariant. We derive
its real space representation that involves nearest and
next-to-nearest-neighbors pairing. Finally, we show that the emerging chiral
Majorana fermions are indeed robust against static disorder. This analysis has
potential applications to quantum simulations and experiments in high-
superconductors.Comment: revtex4 file, color figure
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