19,622 research outputs found
A Walsh-Fourier approach to the circulant Hadamard conjecture
We describe an approach to the circulant Hadamard conjecture based on
Walsh-Fourier analysis. We show that the existence of a circulant Hadamard
matrix of order is equivalent to the existence of a non-trivial solution of
a certain homogenous linear system of equations. Based on this system, a
possible way of proving the conjecture is proposed.Comment: 8 page
Novel Phases and Finite-Size Scaling in Two-Species Asymmetric Diffusive Processes
We study a stochastic lattice gas of particles undergoing asymmetric
diffusion in two dimensions. Transitions between a low-density uniform phase
and high-density non-uniform phases characterized by localized or extended
structure are found. We develop a mean-field theory which relates
coarse-grained parameters to microscopic ones. Detailed predictions for
finite-size () scaling and density profiles agree excellently with
simulations. Unusual large- behavior of the transition point parallel to
that of self-organized sandpile models is found.Comment: 7 pages, plus 6 figures uuencoded, compressed and appended after
source code, LATeX, to be published as a Phys. Rev. Let
A probabilistic and information theoretic interpretation of quantum evolutions
In quantum mechanics, outcomes of measurements on a state have a
probabilistic interpretation while the evolution of the state is treated
deterministically. Here we show that one can also treat the evolution as being
probabilistic in nature and one can measure `which unitary' happened. Likewise,
one can give an information-theoretic interpretation to evolutions by defining
the entropy of a completely positive map. This entropy gives the rate at which
the informational content of the evolution can be compressed. One cannot
compress this information and still have the evolution act on an unknown state,
but we demonstrate a general scheme to do so probabilistically. This allows one
to generalize super-dense coding to the sending of quantum information. One can
also define the ``interaction-entanglement'' of a unitary, and concentrate this
entanglement.Comment: 9 page
A survey of airborne radar systems for deployment on a High Altitude Powered Platform (HAPP)
A survey was conducted to find out the system characteristics of commercially available and unclassified military radars suitable for deployment on a stationary platform. A total of ten domestic and eight foreign manufacturers of the radar systems were identified. Questionnaires were sent to manufacturers requesting information concerning the system characteristics: frequency, power used, weight, volume, power radiated, antenna pattern, resolution, display capabilities, pulse repetition frequency, and sensitivity. A literature search was also made to gather the system characteristics information. Results of the survey are documented and comparisons are made among available radar systems
A high specific capacity membraneless aluminum-air cell operated with an inorganic/organic hybrid electrolyte
Aluminum-air cells have attracted a lot of interests because they have the highest volumetric capacity density in theory among the different metal-air systems. To overcome the self-discharge issue of aluminum, a microfluidic aluminum-air cell working with KOH methanol-based anolyte was developed in this work. A specific capacity up to 2507 mAh g¯¹ (that is, 84.1% of the theoretical value) was achieved experimentally. The KOH concentration and water content in the methanol-based anolyte were found to have direct influence on the cell performance. A possible mechanism of the aluminum reactions in KOH methanol-based electrolyte was proposed to explain the observed phenomenon
Effect of Strong Disorder in a 3-Dimensional Topological Insulator: Phase Diagram and Maps of the Z2 Invariant
We study the effect of strong disorder in a 3-dimensional topological
insulators with time-reversal symmetry and broken inversion symmetry. Firstly,
using level statistics analysis, we demonstrate the persistence of delocalized
bulk states even at large disorder. The delocalized spectrum is seen to display
the levitation and pair annihilation effect, indicating that the delocalized
states continue to carry the Z2 invariant after the onset of disorder.
Secondly, the Z2 invariant is computed via twisted boundary conditions using an
efficient numerical algorithm. We demonstrate that the Z2 invariant remains
quantized and non-fluctuating even after the spectral gap becomes filled with
dense localized states. In fact, our results indicate that the Z2 invariant
remains quantized until the mobility gap closes or until the Fermi level
touches the mobility edges. Based on such data, we compute the phase diagram of
the Bi2Se3 topological material as function of disorder strength and position
of the Fermi level.Comment: references added; final versio
Possible Existence of an Extraordinary Phase in the Driven Lattice Gas
We report recent simulation results which might indicate the existence of a
new low-temperature "phase" in an Ising lattice gas, driven into a
non-equilibrium steady state by an external field. It appears that this
"phase", characterized by multiple-strip configurations, is selected when
square systems are used to approach the thermodynamic limit. We propose a
quantitative criterion for the existence of such a "phase". If confirmed, its
observation may resolve a long-standing controversy over the critical
properties of the driven Ising lattice gas.Comment: 10 pages; 4 figure
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