Coexistence of composite bosons and composite fermions in nu = 1/2 + 1/2 quantum Hall bilayers.
Phys Rev Lett 91:4 (2003) 046803
Abstract:
In bilayer quantum Hall systems at filling fractions near nu=1/2+1/2, as the spacing d between the layers is continuously decreased, intralayer correlations must be replaced by interlayer correlations, and the composite fermion (CF) Fermi seas at large d must eventually be replaced by a composite boson (CB) condensate or "111 state" at small d. We propose a scenario where CBs and CFs coexist in two interpenetrating fluids in the transition. Trial wave functions describing these mixed CB-CF states compare very favorably with exact diagonalization results. A Chern-Simons transport theory is constructed that is compatible with experiment.Conductivity of Paired Composite Fermions
Physical Review Letters 91:4 (2003)
Abstract:
We develop a phenomenological description of the [Formula presented] quantum Hall state in which the Halperin-Lee-Read theory of the half-filled Landau level is combined with a [Formula presented]-wave pairing interaction between composite fermions (CFs). The electromagnetic response functions for the resulting mean-field superconducting state of the CFs are calculated and used in an RPA calculation of the [Formula presented] and [Formula presented] dependent longitudinal conductivity of the physical electrons, a quantity which can be measured experimentally. © 2003 The American Physical Society.Optimizing MIMO antenna systems with channel covariance feedback
IEEE Journal on Selected Areas in Communications 21:3 (2003) 406-417
Abstract:
In this paper, we consider a narrowband point-to-point communication system with nT transmitters and nR receivers. We assume the receiver has perfect knowledge of the channel, while the transmitter has no channel knowledge. We consider the case where the receiving antenna array has uncorrelated elements, while the elements of the transmitting array are arbitrarily correlated. Focusing on the case where nT = 2, we derive simple analytic expressions for the ergodic average and the cumulative distribution function of the mutual information for arbitrary input (transmission) signal covariance. We then determine the ergodic and outage capacities and the associated optimal input signal covariances. We thus show how a transmitter with covariance knowledge should correlate its transmissions to maximize throughput. These results allow us to derive an exact condition (both necessary and sufficient) that determines when beamforming is optimal for systems with arbitrary number of transmitters and receivers.Monte Carlo evaluation of non-abelian statistics
Physical Review Letters 90:1 (2003)
Abstract:
A numerical method was formulated to study braiding statistics of FQH excitations. The method was applied to perform the first direct calculation of the non-Abelian statistics in the MR state. Results confirm previous data drawn within the CFT framework.A model to calculate the capacity distribution of correlated MIMO channels and interferers
Institute of Electrical and Electronics Engineers (IEEE) 4 (2003) 1791-1796