106,042 research outputs found

    The origin of scale-scale correlations of the density perturbations during inflation

    Get PDF
    We show that scale-scale correlations are a generic feature of slow-roll inflation theories. These correlations result from the long-time tails characteristic of the time dependent correlations because the long wavelength density perturbation modes are diffusion-like. A relationship between the scale-scale correlations and time-correlations is established providing a way to reveal the time correlations of the perturbations during inflation. This mechanism provides for a testable prediction that the scale-scale correlations at two different spatial points will vanish.Comment: Accepted for publication, International Journal of Modern Physics, vol. 8 No.6 (Dec 1999

    Nonequilibrium noise correlations in a point contact of helical edge states

    Full text link
    We investigate theoretically the nonequilibrium finite-frequency current noise in a four-terminal quantum point contact of interacting helical edge states at a finite bias voltage. Special focus is put on the effects of the single-particle and two-particle scattering between the two helical edge states on the fractional charge quasiparticle excitations shown in the nonequilibrium current noise spectra. Via the Keldysh perturbative approach, we find that the effects of the single-particle and the two-particle scattering processes on the current noise depend sensitively on the Luttinger liquid parameter. Moreover, the Fano factors for the auto- and cross correlations of the currents in the terminals are distinct from the ones for tunneling between the chiral edge states in the quantum Hall liquid. The current noise spectra in the single-particle-scattering-dominated and the two-particle-scattering-dominated regime are shown. Experimental implications of our results on the transport through the helical edges in two-dimensional topological insulators are discussed.Comment: 10 pages, 8 figure

    Rate of Convergence in Nonlinear Hartree Dynamics with Factorized Initial Data

    Full text link
    The mean field dynamics of an NN-particle weekly interacting Boson system can be described by the nonlinear Hartree equation. In this paper, we present estimates on the 1/N rate of convergence of many-body Schr\"{o}dinger dynamics to the one-body nonlinear Hartree dynamics with factorized initial data with two-body interaction potential VV in L3(R3)+L(R3)L^3 (\mathbb{R}^3)+ L^{\infty} (\mathbb{R}^3).Comment: AMS LaTex, 21 page

    Dissipationless Anomalous Hall Current in the Ferromagnetic Spinel CuCr2_2Se4x_{4-x}Brx_x

    Full text link
    In a ferromagnet, an applied electric field E\bf E invariably produces an anomalous Hall current JH{\bf J}_H that flows perpendicular to the plane defined by E\bf E and M\bf M (the magnetization). For decades, the question whether JH{\bf J}_H is dissipationless (independent of the scattering rate), has been keenly debated without experimental resolution. In the ferromagnetic spinel CuCr2_2Se4x_{4-x}Brx_x, the resistivity ρ\rho (at low temperature) may be increased 1000 fold by varying xx(Br), without degrading the M\bf M. We show that JH/E{\bf J}_H/E (normalized per carrier, at 5 K) remains unchanged throughout. In addition to resolving the controversy experimentally, our finding has strong bearing on the generation and study of spin-Hall currents in bulk samples.Comment: 7 pages, 6 figure
    corecore