16,575 research outputs found
High quality epitaxial ZnSe and the relationship between electron mobility and photoluminescence characteristics
High quality epitaxial layers of nominally undoped ZnSe have been grown by metalorganic chemical vapor deposition at low temperature (325 °C) and pressure (30 Torr), using dimethylzinc and hydrogen selenide. All layers were unintentionally doped n type with net carrier concentrations of 6.4×10^(14)–1.5×10^(16) cm^(−3) and exhibited very high mobility at room temperature (up to 500 cm2/V s) as well as at 77 K, where the measured value of 9250 cm^2/V s is the highest so far reported for vapor phase growth. Additional evidence for the high quality of the material is provided by photoluminescence. Experimental results indicate a correlation between the photoluminescence characteristics and the electrical properties that may be useful in assessing the quality of ZnSe films
Poincare's Recurrence Theorem and the Unitarity of the S matrix
A scattering process can be described by suitably closing the system and
considering the first return map from the entrance onto itself. This scattering
map may be singular and discontinuous, but it will be measure preserving as a
consequence of the recurrence theorem applied to any region of a simpler map.
In the case of a billiard this is the Birkhoff map. The semiclassical
quantization of the Birkhoff map can be subdivided into an entrance and a
repeller. The construction of a scattering operator then follows in exact
analogy to the classical process. Generically, the approximate unitarity of the
semiclassical Birkhoff map is inherited by the S-matrix, even for highly
resonant scattering where direct quantization of the scattering map breaks
down.Comment: 4 latex pages, 5 ps figure
On the sources of static plane symmetric vacuum space-times
The static vacuum plane spacetimes are considered, which have two non-trivial
solutions: The Taub solution and the Rindler solution. Imposed reflection
symmetry, we find that the source for the Taub solution does not satisfy any
energy conditions, which is consistent with previous studies, while the source
for the Rindler solution satisfies the weak and strong energy conditions (but
not the dominant one). It is argued that the counterpart of the Einstein theory
to the gravitational field of a massive Newtonian plane should be described by
the Rindler solution, which represents also a uniform gravitational field
A numerical study of the spectrum and eigenfunctions on a tubular arc
The Hamiltonian for a particle constrained to move on the surface of a curved
nanotube is derived using the methods of differential forms. A two-dimensional
Gram-Schmidt orthonormalization procedure is employed to calculate basis
functions for determining the eigenvalues and eigenstates of a tubular arc (a
nanotube in the shape of a hyperbolic cosine) with several hundred scattering
centers. The curvature of the tube is shown to induce bound states that are
dependent on the curvature parameters and bend location of the tube.Comment: 14 pages, 5 tables, 6 figure
Nonuniversality in the pair contact process with diffusion
We study the static and dynamic behavior of the one dimensional pair contact
process with diffusion. Several critical exponents are found to vary with the
diffusion rate, while the order-parameter moment ratio m=\bar{rho^2}
/\bar{rho}^2 grows logarithmically with the system size. The anomalous behavior
of m is traced to a violation of scaling in the order parameter probability
density, which in turn reflects the presence of two distinct sectors, one
purely diffusive, the other reactive, within the active phase. Studies
restricted to the reactive sector yield precise estimates for exponents beta
and nu_perp, and confirm finite size scaling of the order parameter. In the
course of our study we determine, for the first time, the universal value m_c =
1.334 associated with the parity-conserving universality class in one
dimension.Comment: 9 pages, 5 figure
Scaling behavior of the directed percolation universality class
In this work we consider five different lattice models which exhibit
continuous phase transitions into absorbing states. By measuring certain
universal functions, which characterize the steady state as well as the
dynamical scaling behavior, we present clear numerical evidence that all models
belong to the universality class of directed percolation. Since the considered
models are characterized by different interaction details the obtained
universal scaling plots are an impressive manifestation of the universality of
directed percolation.Comment: 24 pages, 7 figures, accepted for publication in Nuclear Physics
Bayesian analysis of genetic change due to selection using Gibbs sampling
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