201,101 research outputs found
Tailorable infrared sensing device with strain layer superlattice structure
An infrared photodetector is formed of a heavily doped p-type Ge sub x Si sub 1-x/Si superlattice in which x is pre-established during manufacture in the range 0 to 100 percent. A custom-tailored photodetector that can differentiate among close wavelengths in the range of 2.7 to 50 microns is fabricated by appropriate selection of the alloy constituency value, x, to establish a specific wavelength at which photodetection cutoff will occur
Diffusion semigroup on manifolds with time-dependent metrics
Let , on a differential manifold equipped
with time-depending complete Riemannian metric , where
is the Laplacian induced by and is a
family of -vector fields. We first present some explicit criteria for
the non-explosion of the diffusion processes generated by ; then establish
the derivative formula for the associated semigroup; and finally, present a
number of equivalent semigroup inequalities for the curvature lower bound
condition, which include the gradient inequalities, transportation-cost
inequalities, Harnack inequalities and functional inequalities for the
diffusion semigroup
Einstein-Gauss-Bonnet Black Strings at Large
We study the black string solutions in the Einstein-Gauss-Bonnet(EGB) theory
at large . By using the expansion in the near horizon region we derive
the effective equations that describe the dynamics of the EGB black strings.
The uniform and non-uniform black strings are obtained as the static solutions
of the effective equations. From the perturbation analysis of the effective
equations, we find that thin EGB black strings suffer from the Gregory-Laflamme
instablity and the GB term weakens the instability when the GB coefficient is
small, however, when the GB coefficient is large the GB term enhances the
instability. Furthermore, we numerically solve the effective equations to study
the non-linear instability. It turns out that the thin black strings are
unstable to developing inhomogeneities along their length, and at late times
they asymptote to the stable non-uniform black strings. The behavior is
qualitatively similar to the case in the Einstein gravity. Compared with the
black string instability in the Einstein gravity at large D, when the GB
coefficient is small the time needed to reach to final state increases, but
when the GB coefficient is large the time to reach to final state decreases.
Starting from the point of view in which the effective equations can be
interpreted as the equations for the dynamical fluid, we evaluate the transport
coefficients and find that the ratio of the shear viscosity and the entropy
density agrees with that obtained previously in the membrane paradigm after
taking the large limit.Comment: 22 pages, 8 figures, some errors corrected, references adde
Asymptotic Glosten Milgrom equilibrium
This paper studies the Glosten Milgrom model whose risky asset value admits
an arbitrary discrete distribution. Contrast to existing results on insider's
models, the insider's optimal strategy in this model, if exists, is not of
feedback type. Therefore a weak formulation of equilibrium is proposed. In this
weak formulation, the inconspicuous trade theorem still holds, but the
optimality for the insider's strategy is not enforced. However, the insider can
employ some feedback strategy whose associated expected profit is close to the
optimal value, when the order size is small. Moreover this discrepancy
converges to zero when the order size diminishes. The existence of such a weak
equilibrium is established, in which the insider's strategy converges to the
Kyle optimal strategy when the order size goes to zero
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