13,946 research outputs found
Prying the lid from the black box: Plotting evaluation strategy for welfare employment and training programs
Superfield Realizations of Lorentz and CPT Violation
Superfield realizations of Lorentz-violating extensions of the Wess-Zumino
model are presented. These models retain supersymmetry but include terms that
explicitly break the Lorentz symmetry. The models can be understood as arising
from superspace transformations that are modifications of the familiar one in
the Lorentz-symmetric case.Comment: 10 page
Dynamical mapping method in nonrelativistic models of quantum field theory
The solutions of Heisenberg equations and two-particles eigenvalue problems
for nonrelativistic models of current-current fermion interaction and model are obtained in the frameworks of dynamical mapping method. The
equivalence of different types of dynamical mapping is shown. The connection
between renormalization procedure and theory of selfadjoint extensions is
elucidated.Comment: 14 page
The Free Quon Gas Suffers Gibbs' Paradox
We consider the Statistical Mechanics of systems of particles satisfying the
-commutation relations recently proposed by Greenberg and others. We show
that although the commutation relations approach Bose (resp.\ Fermi) relations
for (resp.\ ), the partition functions of free gases are
independent of in the range . The partition functions exhibit
Gibbs' Paradox in the same way as a classical gas without a correction factor
for the statistical weight of the -particle phase space, i.e.\ the
Statistical Mechanics does not describe a material for which entropy, free
energy, and particle number are extensive thermodynamical quantities.Comment: number-of-pages, LaTeX with REVTE
All-Optical Switching with Transverse Optical Patterns
We demonstrate an all-optical switch that operates at ultra-low-light levels
and exhibits several features necessary for use in optical switching networks.
An input switching beam, wavelength , with an energy density of
photons per optical cross section [] changes
the orientation of a two-spot pattern generated via parametric instability in
warm rubidium vapor. The instability is induced with less than 1 mW of total
pump power and generates several Ws of output light. The switch is
cascadable: the device output is capable of driving multiple inputs, and
exhibits transistor-like signal-level restoration with both saturated and
intermediate response regimes. Additionally, the system requires an input power
proportional to the inverse of the response time, which suggests thermal
dissipation does not necessarily limit the practicality of optical logic
devices
Space construction system analysis. Part 2: Platform definition
The top level system requirements are summarized and the accompanying conceptual design for an engineering and technology verification platform (ETVP) system is presented. An encompassing statement of the system objectives which drive the system requirements is presented and the major mission and subsystem requirements are described with emphasis on the advanced communications technology mission payload. The platform design is defined and used as a reference configuration for an end to space construction analyses. The preferred construction methods and processes, the important interactions between the platform design and the construction system design and operation, and the technology development efforts required to support the design and space construction of the ETVP are outlined
Spacelike Ricci Inheritance Vectors in a Model of String Cloud and String Fluid Stress Tensor
We study the consequences of the existence of spacelike Ricci inheritance
vectors (SpRIVs) parallel to for model of string cloud and string fluid
stress tensor in the context of general relativity. Necessary and sufficient
conditions are derived for a spacetime with a model of string cloud and string
fluid stress tensor to admit a SpRIV and a SpRIV which is also a spacelike
conformal Killing vector (SpCKV). Also, some results are obtained.Comment: 11 page
Planet Formation in the Outer Solar System
This paper reviews coagulation models for planet formation in the Kuiper
Belt, emphasizing links to recent observations of our and other solar systems.
At heliocentric distances of 35-50 AU, single annulus and multiannulus
planetesimal accretion calculations produce several 1000 km or larger planets
and many 50-500 km objects on timescales of 10-30 Myr in a Minimum Mass Solar
Nebula. Planets form more rapidly in more massive nebulae. All models yield two
power law cumulative size distributions, N_C propto r^{-q} with q = 3.0-3.5 for
radii larger than 10 km and N_C propto r^{-2.5} for radii less than 1 km. These
size distributions are consistent with observations of Kuiper Belt objects
acquired during the past decade. Once large objects form at 35-50 AU,
gravitational stirring leads to a collisional cascade where 0.1-10 km objects
are ground to dust. The collisional cascade removes 80% to 90% of the initial
mass in the nebula in roughly 1 Gyr. This dust production rate is comparable to
rates inferred for alpha Lyr, beta Pic, and other extrasolar debris disk
systems.Comment: invited review for PASP, March 2002. 33 pages of text and 12 figure
Low-frequency measurement of the tunneling amplitude in a flux qubit
We have observed signatures of resonant tunneling in an Al three-junction
qubit, inductively coupled to a Nb LC tank circuit. The resonant properties of
the tank oscillator are sensitive to the effective susceptibility (or
inductance) of the qubit, which changes drastically as its flux states pass
through degeneracy. The tunneling amplitude is estimated from the data. We find
good agreement with the theoretical predictions in the regime of their
validity.Comment: REVTeX4, 3pp., 3 EPS figures. v2: new sample, textual clarifications.
v3: minor polishing; final, to appear in PRB Rapid
Phase Transition of XY Model in Heptagonal Lattice
We numerically investigate the nature of the phase transition of the XY model
in the heptagonal lattice with the negative curvature, in comparison to other
interaction structures such as a flat two-dimensional (2D) square lattice and a
small-world network. Although the heptagonal lattice has a very short
characteristic path length like the small-world network structure, it is
revealed via calculation of the Binder's cumulant that the former exhibits a
zero-temperature phase transition while the latter has the finite-temperature
transition of the mean-field nature. Through the computation of the vortex
density as well as the correlation function in the low-temperature
approximation, we show that the absence of the phase transition originates from
the strong spinwave-type fluctuation, which is discussed in relation to the
usual 2D XY model.Comment: 5 pages, 6 figures, to be published in Europhys. Let
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