Magnetotransport in the presence of a longitudinal barrier: multiple quantum interference of edge states

Transport in a two-dimensional electron gas subject to an external magnetic field is analyzed in the presence of a \textit{longitudinal barrier.} We show that \textit{quantum interference of the edge states} bound by the longitudinal barrier results in a drastic change of the electron motion: the degenerate discrete Landau levels are transformed into an alternating sequence of energy bands and energy gaps. These features of the electron spectrum should result in a high sensitivity of thermodynamic and transport properties of the 2D electron gas to external fields. In particular, we predict giant oscillations of the ballistic conductance and discuss nonlinear current-voltage characteristics, coherent Bloch oscillations and effects of impuritiesComment: 4 pages, 3 figure

The Generalized Method of Moments

We continue presenting recent achievements in econometrics not yet widely known to a Russian reader. The generalized method of moments (GMM) was introduced to econometrical research by L. Hansen in his seminal paper in 1982. The GMM is a result of unifying two main approaches to estimating model parameters — method of moments (MM) and generalized least squares (GLS). In the paper it is shown how to use the GMM in the case of a linear regression modelasymptotic normality; consistent estimator; instrumental variables; method of moments

Magnetic breakdown induced Peierls transition

We predict the new type of phase transition in quasi one-dimensional system of interacting electrons at high magnetic fields, the stabilization of a density wave which transforms a two dimensional open Fermi surface into a periodic chain of large pockets with small distances between them. We show that quantum tunneling of electrons between the neighboring closed orbits enveloping these pockets transforms the electron spectrum into a set of extremely narrow energy bands and gaps that decreases the total electron energy, thus leading to a \emph{magnetic breakdown induced density wave} ground state analogous to the well-known instability of Peierls type.Comment: 4 pages, 4 figures; accepted for publication in Phys. Rev. Letter

Coulomb Ordering in Anderson-Localized Electron Systems

We consider an electron system under conditions of strong Anderson localization, taking into account interelectron long-range Coulomb repulsion. We have established that with the electron density going to zero the Coulomb interaction brings the arrangement of the Anderson localized electrons closer and closer to an ideal (Wigner) crystal lattice, provided the temperature is sufficiently low and the dimension of the system is > 1. The ordering occurs despite the fact that a random spread of the energy levels of the localized one-electron states, exceeding the mean Coulomb energy per electron, renders it impossible the electrons to be self-localized due to their mutual Coulomb repulsion This differs principally the Coulomb ordered Anderson localized electron system (COALES) from Wigner crystal, Wigner glass, and any other ordered electron or hole system that results from the Coulomb self-localization of electrons/holes. The residual disorder inherent to COALES is found to bring about a multi-valley ground-state degeneration akin to that in spin glass. With the electron density increasing, COALES is revealed to turn into Wigner glass or a glassy state of a Fermi-glass type depending on the width of the random spread of the electron levels.Comment: 4 pages, LaTeX 2.09, To appear in Phys.Rev B Rapid Communications, The abstract and the Introduction have been written anew to stress a principal difference between a new macroscopical state predicted in the paper and Wigner crystal or Wigner glass, some notations have been change

Bayesian analysis in the case of an estimated parameter following a stochastic process

We perform Bayesian analysis of the sequence of unknown means mi given observations Xi under the assumption that, for any k > 0, the first k members X1, X2, …, Xk are normally distributed with the mean (m1,…, mk ) and a known covariance matrix. It is assumed that the parameters m1,…, mk,… follow a Gaussian process We prove that, for any fixed k, the covariance matrices of marginal posterior distributions converge In the case of a Gaussian AR(1) process analytic expression for the asymptotic posterior structure is givenasymptotic covariance matrix; Bayes’ rule; Gaussian process; marginal posterior distribution

Stability Tests for Linear Regression Models

A number of common tests for stability of a classical linear regression model are considered in the paper. The case where a point of structural change is not known in advance has been given a special treatmentnested and non-nested models; recursive tests; stability; structural change

Non-Makovian decoherence of a two-level system weakly coupled to a bosonic bath

Bloch-Redfield equation is a common tool for studying evolution of qubit systems weakly coupled to environment. We investigate the accuracy of the Born approximation underlying this equation. We find that the high order terms in the perturbative expansion contain accumulating divergences that make straightforward Born approximation inappropriate. We develop diagrammatic technique to formulate, and solve the improved self-consistent Born approximation. This more accurate treatment reveals an exponential time dependent prefactor in the non-Markovian contribution dominating the qubit long-time relaxation found in Phys. Rev. B 71, 035318 (2005). At the same time, the associated dephasing is not affected and is described by the Born-Markov approximation.Comment: To appear in EuroPhys. Let

Giant oscillations of the current in a dirty 2D electron system flowing perpendicular to a lateral barrier under magnetic field

The charge transport in a dirty 2-dimensional electron system biased in the presence of a lateral potential barrier under magnetic field is theoretically studied. The quantum tunneling across the barrier provides the quantum interference of the edge states localized on its both sides that results in giant oscillations of the charge current flowing perpendicular to the lateral junction. Our theoretical analysis is in a good agreement with the experimental observations presented in Ref.8. In particular, positions of the conductance maxima coincide with the Landau levels while the conductance itself is essentially suppressed even at the energies at which the resonant tunneling occurs and hence these puzzling observations can be resolved without taking into account the electron-electron interaction.Comment: 6 pages, 4 figure

Inflation and Stock Market: CPI and S&P

Empirical/statistical analysis of effects of changes in index S&P 500 upon inflation processes in American economy in the years 1951–2009 is given. It is shown there is a statistically significant difference in CPI changes dependent on positive (negative) dynamics of index S&P 500 oneshypothesis testing; index S&P 500; inflation; Welsh test