45,653 research outputs found
Random access-random release relay switching matrix
XY relay switching matrix provides complete random access and random release of 400 points. A mercury-wetted bistable relay with independent set and reset coils is the unique feature associated with each point
Small-angle scattering in a marginal Fermi-liquid
We study the magnetotransport properties of a model of small-angle scattering
in a marginal Fermi liquid. Such a model has been proposed by Varma and
Abrahams [Phys. Rev. Lett. 86, 4652 (2001)] to account for the anomalous
temperature dependence of in-plane magnetotransport properties of the high-Tc
cuprates. We study the resistivity, Hall angle and magnetoresistance using both
analytical and numerical techniques. We find that small-angle scattering only
generates a new temperature dependence for the Hall angle near particle-hole
symmetric Fermi surfaces where the conventional Hall term vanishes. The
magnetoresistance always shows Kohler's rule behavior.Comment: 4 pages, 3 figures, Revtex
Phase diagram and quasiparticle properties of the Hubbard model within cluster two-site DMFT
We present a cluster dynamical mean-field treatment of the Hubbard model on a
square lattice to study the evolution of magnetism and quasiparticle properties
as the electron filling and interaction strength are varied. Our approach for
solving the dynamical mean-field equations is an extension of Potthoff's
"two-site" method [Phys. Rev. B. 64, 165114 (2001)] where the self-consistent
bath is represented by a highly restricted set of states. As well as the
expected antiferromagnetism close to half filling, we observe distortions of
the Fermi surface. The proximity of a van Hove point and the incipient
antiferromagnetism lead to the evolution from an electron-like Fermi surface
away from the Mott transition, to a hole-like one near half-filling. Our
results also show a gap opening anisotropically around the Fermi surface close
to the Mott transition (reminiscent of the pseudogap phenomenon seen in the
cuprate high-Tc superconductors). This leaves Fermi arcs which are closed into
pockets by lines with very small quasiparticle residue.Comment: 10 pages, 8 figures, latex (revtex4
Symplectic structure for elastic and chiral conducting cosmic string models
This article is based on the covariant canonical formalism and corresponding
symplectic structure on phase space developed by Witten, Zuckerman and others
in the context of field theory. After recalling the basic principles of this
procedure, we construct the conserved bilinear symplectic current for generic
elastic string models. These models describe current carrying cosmic strings
evolving in an arbitrary curved background spacetime. Particular attention is
paid to the special case of the chiral string for which the worldsheet current
is null. Different formulations of the chiral string action are discussed in
detail, and as a result the integrability property of the chiral string is
clarified.Comment: 18 page
Lessons in Failure: The Rice Growers Association Cooperative
This empirical study investigates a large California cooperative's closure and identifies lessons learned that might be useful to other cooperatives. It was found that the cooperative's directors failed to effectively supervise management. In turn, management fell short of expectations to fully evaluate complex business decisions.Agribusiness,
MARKET REFORMS VERSUS STRUCTURAL REFORMS IN RURAL CHINA
This paper adds to the debate on the impact of market reforms versus structural reforms in explaining agricultural output growth in China. A multiple-output stochastic frontier and a technical inefficiency equation are estimated using provincial data on the rural economy from 1986 to 1995. Grain self-sufficiency policies and incomplete market reforms in the 1980s and 1990s led to allocative inefficiency. Agricultural disinvestment shrunk the production frontier and the fragmentation of land holdings reduced technical efficiency. China's rural economic reform is far from being complete.Agricultural and Food Policy, O47, Q12, Q15,
Transonic Elastic Model for Wiggly Goto-Nambu String
The hitherto controversial proposition that a ``wiggly" Goto-Nambu cosmic
string can be effectively represented by an elastic string model of exactly
transonic type (with energy density inversely proportional to its tension
) is shown to have a firm mathematical basis.Comment: 8 pages, plain TeX, no figure
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