Possible Detection of Causality Violation in a Non-local Scalar Model

We consider the possibility that there may be causality violation detectable at higher energies. We take a scalar nonlocal theory containing a mass scale $\Lambda$ as a model example and make a preliminary study of how the causality violation can be observed. We show how to formulate an observable whose detection would signal causality violation. We study the range of energies (relative to $\Lambda$) and couplings to which the observable can be used.Comment: Latex, 30 page

Fourier Response of a Memristor: Generation of High Harmonics with Increasing Weights

We investigate the Fourier transform of the current through a memristor when the applied-voltage frequency is smaller than the characteristic memristor frequency, and the memristor shows hysteresis in the current-voltage plane. We find that when the hysteresis curve is "smooth", the current Fourier transform has weights at odd and even harmonics that decay rapidly and monotonically with the order of the harmonic; when the hysteresis curve is "sharp", the Fourier transform of the current is significantly broader, with non-monotonic weights at high harmonics. We present a simple model which shows that this qualitative change in the Fourier spectrum is solely driven by the saturation of memristance during a voltage cycle, and not independently by various system parameters such as applied or memristor frequencies, and the non-linear dopant drift.Comment: 5 pages, 3 figure

Relating Green's Functions in Axial and Lorentz Gauges using Finite Field-Dependent BRS Transformations

We use finite field-dependent BRS transformations (FFBRS) to connect the Green functions in a set of two otherwise unrelated gauge choices. We choose the Lorentz and the axial gauges as examples. We show how the Green functions in axial gauge can be written as a series in terms of those in Lorentz gauges. Our method also applies to operator Green's functions. We show that this process involves another set of related FFBRS transfomations that is derivable from infinitesimal FBRS. We suggest possible applications.Comment: 20 pages, LaTex, Section 4 expanded, typos corrected; last 2 references modified; (this) revised version to appear in J. Math. Phy

Zero-bias conductance anomaly in bilayer quantum Hall systems

Bilayer quantum Hall system at total filling factor $\nu=1$ shows a rich variety of broken symmetry ground states because of the competition between the interlayer and intralayer Coulomb interactions. When the layers are sufficiently close, a bilayer system develops spontaneous interlayer phase-coherence that manifests itself through a spectacular enhancement of the zero-bias interlayer tunneling conductance. We present a theory of this tunneling conductance anomaly, and show that the zero-bias conductance is proportional to the square of the {\it quasiparticle} tunneling amplitude.Comment: 3 pages, 1 figure. To appear in the PPHMF-IV conference proceedings. (For more details, see cond-mat/0103454) New version contains two added reference