2,140,553 research outputs found
Increased voltage photovoltaic cell
A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer
Emergence of Classical Orbits in Few-Cycle Above-Threshold Ionization
The time-dependent Schr\"odinger equation for atomic hydrogen in few-cycle
laser pulses is solved numerically. Introducing a positive definite quantum
distribution function in energy-position space, a straightforward comparison of
the numerical ab initio results with classical orbit theory is facilitated.
Integration over position space yields directly the photoelectron spectra so
that the various pathways contributing to a certain energy in the photoelectron
spectra can be established in an unprecedented direct and transparent way.Comment: 4 pages, 4 figures REVTeX (manuscript with higher resolution figures
available at http://www.dieterbauer.de/publist.html
Nucleon and Pion Form Factors in Different Forms of Relativistic Quantum Mechanics
Calculations of form factors in different forms of relativistic kinematics
are presented. They involve the instant, front and point forms. In the two
first cases, different kinematical conditions are considered while in the
latter case, both a Dirac-inspired approach and a hyperplane-based one are
incorporated in our study. Numerical results are presented for the pion form
factors with emphasis on both the low and high Q**2 range. A new argument is
presented, explaining why some approaches do considerably much better than
other ones whenonly a single-particle current is considered.Comment: To appear in the proceedings of MENU04 (Beijing, Aug. 29- Sept. 4,
2004
Implicit Solutions of PDE's
Further investigations of implicit solutions to non-linear partial
differential equations are pursued. Of particular interest are the equations
which are Lorentz invariant. The question of which differential equations of
second order for a single unknown are solved by the imposition of an
inhomogeneous quadratic relationship among the independent variables, whose
coefficients are functions of is discussed, and it is shown that if the
discriminant of the quadratic vanishes, then an implicit solution of the
so-called Universal Field Equation is obtained. The relation to the general
solution is discussed.Comment: 11 pages LaTeX2
The size of flavor changing effects induced by the symmetry breaking sector
It has recently been shown that strong interactions underlying electroweak
symmetry breaking will induce four-fermion amplitudes proportional to m_t^2,
which in turn will influence a variety of flavor changing processes. We argue
that the size of these effects are likely to be far below the current
experimental bounds.Comment: 5 pages, LaTeX, 1 figur
Hierarchic trees with branching number close to one: noiseless KPZ equation with additional linear term for imitation of 2-d and 3-d phase transitions.
An imitation of 2d field theory is formulated by means of a model on the
hierarhic tree (with branching number close to one) with the same potential and
the free correlators identical to 2d correlators ones.
Such a model carries on some features of the original model for certain scale
invariant theories. For the case of 2d conformal models it is possible to
derive exact results. The renormalization group equation for the free energy is
noiseless KPZ equation with additional linear term.Comment: latex, 5 page
Wilson's renormalization group applied to 2D lattice electrons in the presence of van Hove singularities
The weak coupling instabilities of a two dimensional Fermi system are
investigated for the case of a square lattice using a Wilson renormalization
group scheme to one loop order. We focus on a situation where the Fermi surface
passes through two saddle points of the single particle dispersion. In the case
of perfect nesting, the dominant instability is a spin density wave but d-wave
superconductivity as well as charge or spin flux phases are also obtained in
certain regions in the space of coupling parameters. The low energy regime in
the vicinity of these instabilities can be studied analytically. Although
saddle points play a major role (through their large contribution to the single
particle density of states), the presence of low energy excitations along the
Fermi surface rather than at isolated points is crucial and leads to an
asymptotic decoupling of the various instabilities. This suggests a more
mean-field like picture of these instabilities, than the one recently
established by numerical studies using discretized Fermi surfaces.Comment: gzipped tar file, 31 pages including 10 figures, minor correction of
misprint
Hoop/column antenna deployment mechanism overview
The hoop/column antenna program is directed toward the development of a cost effective, large area, self deploying reflector antenna system. Large surface area antenna systems are required in future space missions involving improved land communications, Earth resources observation, and the study of intergalactic energy sources. The hoop/column antenna is a concept where a large antenna system can be packaged within the Space Transportation System (Shuttle) payload bay, launched into Earth orbit where it is released either for deployment as an Earth observation or communications antenna, or boosted into deep space as an intergalactic energy probe. Various mechanisms and support structures are described that are required to deploy the hoop, which is used to support the antenna reflective surface, and the column that is used to position the antenna feeds and the reflector. It also describes a proof-of-concept model (15 meters in diameter) that is currently being ground tested to determine the adequacy of the deployment mechanisms
Computer program provides linear sampled- data analysis for high order systems
Computer program performs transformations in the order S-to W-to Z to allow arithmetic to be completed in the W-plane. The method is based on a direct transformation from the S-plane to the W-plane. The W-plane poles and zeros are transformed into Z-plane poles and zeros using the bilinear transformation algorithm
Evaluating cumulative ascent: Mountain biking meets Mandelbrot
The problem of determining total distance ascended during a mountain bike
trip is addressed. Altitude measurements are obtained from GPS receivers
utilizing both GPS-based and barometric altitude data, with data averaging used
to reduce fluctuations. The estimation process is sensitive to the degree of
averaging, and is related to the well-known question of determining coastline
length. Barometric-based measurements prove more reliable, due to their
insensitivity to GPS altitude fluctuations.Comment: 10 pages, 9 figures (v.2: minor revisions
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