48,685 research outputs found
Synthesis report with pro-poor trade research findings and policy recommandations
The purpose of the project was to investigate international trade in fisheries products and its relationship to poverty alleviation and livelihoods of poor aquatic resource users in developing countries in Asia, and to identify options to improve the effectiveness of poverty reduction through international seafood trade. The project directly addressed the EC-PREP priority area of trade and development, and indirectly provided valuable insight to two other priority areas: food security and sustainable rural development; and institutional capacity building. [PDF contains 60 pages.
Universality Conjecture for all Airy, Sine and Bessel Kernels in the Complex Plane
We address the question of how the celebrated universality of local
correlations for the real eigenvalues of Hermitian random matrices of size NxN
can be extended to complex eigenvalues in the case of random matrices without
symmetry. Depending on the location in the spectrum, particular large-N limits
(the so-called weakly non-Hermitian limits) lead to one-parameter deformations
of the Airy, sine and Bessel kernels into the complex plane. This makes their
universality highly suggestive for all symmetry classes. We compare all the
known limiting real kernels and their deformations into the complex plane for
all three Dyson indices beta=1,2,4, corresponding to real, complex and
quaternion real matrix elements. This includes new results for Airy kernels in
the complex plane for beta=1,4. For the Gaussian ensembles of elliptic Ginibre
and non-Hermitian Wishart matrices we give all kernels for finite N, built from
orthogonal and skew-orthogonal polynomials in the complex plane. Finally we
comment on how much is known to date regarding the universality of these
kernels in the complex plane, and discuss some open problems.Comment: 16 pages, based on invited talk at MSRI Berkeley, September 201
Recommended from our members
A survey of nearby galaxies for CO
We have made a survey of the nuclei of 81 galaxies for the 1-) line of CO. 38 of the galaxies are from a complete sample with recession velocity ≦400 km s-1 and 21-cm line strength ≧10-27 Wm-2, and the remainder represent nearby galaxies with weaker or no HI, early-type galaxies (E/SO/Sa) with detected HI and active/infrared galaxies.
Galaxies with strong CO lines like M82, NGC253 and IC342 are exceedingly rare: all the galaxies we observed are weaker than 0/2K except the irregular galaxy DDO133 with T*A=0.22K. We have new, confirmed detections of two other irregular galaxies, IC10 and Pegasus, at a weaker level, and unconfirmed detections of the irregular NGC3109 and the nearest Type I Seyfert galaxy NGC4051. We have confirmed the existence of CO in the nucleus of NGC6946 and obtained spectra of new positions in M82 and NGC253
Characteristic polynomials in real Ginibre ensembles
We calculate the average of two characteristic polynomials for the real Ginibre ensemble of asymmetric random matrices, and its chiral counterpart. Considered as quadratic forms they determine a skew-symmetric kernel from which all
complex eigenvalue correlations can be derived. Our results are obtained in a very simple fashion without going to an eigenvalue representation, and are completely new in the chiral case. They hold for Gaussian ensembles which are partly symmetric, with kernels given in terms of Hermite and Laguerre polynomials respectively, depending on an asymmetry parameter. This allows us to interpolate between the maximally asymmetric real Ginibre and the Gaussian Orthogonal Ensemble, as well as their chiral counterparts
Low-noise 1 THz niobium superconducting tunnel junction mixer with a normal metal tuning circuit
We describe a 1 THz quasioptical SIS mixer which uses a twin-slot antenna, an antireflection-coated silicon hyperhemispherical lens, Nb/Al-oxide/Nb tunnel junctions, and an aluminum normal-metal tuning circuit in a two-junction configuration. Since the mixer operates substantially above the gap frequency of niobium (nu >~ 2 Delta/h ~ 700 GHz), a normal metal is used in the tuning circuit in place of niobium to reduce the Ohmic loss. The frequency response of the device was measured using a Fourier transform spectrometer and agrees reasonably well with the theoretical prediction. At 1042 GHz, the uncorrected double-sideband receiver noise temperature is 840 K when the physical temperature of the mixer is 2.5 K. This is the first SIS mixer which outperforms GaAs Schottky diode mixers by a large margin at 1 THz
Random matrix theory of unquenched two-colour QCD with nonzero chemical potential
We solve a random two-matrix model with two real asymmetric matrices whose
primary purpose is to describe certain aspects of quantum chromodynamics with
two colours and dynamical fermions at nonzero quark chemical potential mu. In
this symmetry class the determinant of the Dirac operator is real but not
necessarily positive. Despite this sign problem the unquenched matrix model
remains completely solvable and provides detailed predictions for the Dirac
operator spectrum in two different physical scenarios/limits: (i) the
epsilon-regime of chiral perturbation theory at small mu, where mu^2 multiplied
by the volume remains fixed in the infinite-volume limit and (ii) the
high-density regime where a BCS gap is formed and mu is unscaled. We give
explicit examples for the complex, real, and imaginary eigenvalue densities
including Nf=2 non-degenerate flavours. Whilst the limit of two degenerate
masses has no sign problem and can be tested with standard lattice techniques,
we analyse the severity of the sign problem for non-degenerate masses as a
function of the mass split and of mu.
On the mathematical side our new results include an analytical formula for
the spectral density of real Wishart eigenvalues in the limit (i) of weak
non-Hermiticity, thus completing the previous solution of the corresponding
quenched model of two real asymmetric Wishart matrices.Comment: 45 pages, 31 figures; references added, as published in JHE
Sandblasting nozzle
A nozzle for use with abrasive and/or corrosive materials is formed of sintered ceramic compositions having high temperature oxidation resistance, high hardness and high abrasion and corrosion resistance. The ceramic may be a binary solid solution of a ceramic oxide and silicon nitride, and preferably a ternary solid solution of a ceramic oxide, silicon nitride and aluminum nitride. The ceramic oxide is selected from a group consisting of Al2O3, Y2O3 and Cr2O3, or mixtures of those compounds. Titanium carbide particles are dispersed in the ceramic mixture before sintering. The nozzles are encased for protection from external forces while in use by a metal or plastic casing
What is the problem to which interactive multimedia is the solution?
This is something of an unusual paper. It serves as both the reason for and the result of a small number of leading academics in the field, coming together to focus on the question that serves as the title to this paper: What is the problem to which interactive multimedia is the solution? Each of the authors addresses this question from their own viewpoint, offering informed insights into the development, implementation and evaluation of multimedia. The result of their collective work was also the focus of a Western Australian Institute of Educational Research seminar, convened at Edith Cowan University on 18 October, 1994.
The question posed is deliberately rhetorical - it is asked to allow those represented here to consider what they think are the significant issues in the fast-growing field of multimedia. More directly, the question is also asked here because nobody else has considered it worth asking: for many multimedia is done because it is technically possible, not because it offers anything that is of value or provides the solution to a particular problem.
The question, then, is answered in various ways by each of the authors involved and each, in their own way, consider a range of fundamental issues concerning the nature, place and use of multimedia - both in education and in society generally. By way of an introduction, the following provides a unifying context for the various contributions made here
Quasi-optical SIS mixers with normal metal tuning structures
We recently reported (1996) a quasi-optical SIS mixer which used Nb/Al-oxide/Nb tunnel junctions and a normal-metal (Al) tuning circuit to achieve an uncorrected receiver noise temperature of 840 K (DSB) at 1042 GHz. Here we present results on several different device designs, which together cover the 300-1200 GHz frequency range. The mixers utilize an antireflection-coated silicon hyper-hemispherical lens, a twin-slot antenna, and a two-junction tuning circuit. The broad-band frequency response was measured using Fourier transform spectrometry (FTS), and is in good agreement with model calculations. Heterodyne tests were carried out from 400 GHz up to 1040 GHz, and these measurements agree well with the FTS results and with calculations based on Tucker's theory (1985)
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