6,758 research outputs found
Hypoelliptic heat kernel inequalities on Lie groups
This paper discusses the existence of gradient estimates for second order
hypoelliptic heat kernels on manifolds. It is now standard that such
inequalities, in the elliptic case, are equivalent to a lower bound on the
Ricci tensor of the Riemannian metric. For hypoelliptic operators, the
associated "Ricci curvature" takes on the value -\infty at points of degeneracy
of the semi-Riemannian metric associated to the operator. For this reason, the
standard proofs for the elliptic theory fail in the hypoelliptic setting.
This paper presents recent results for hypoelliptic operators. Malliavin
calculus methods transfer the problem to one of determining certain infinite
dimensional estimates. Here, the underlying manifold is a Lie group, and the
hypoelliptic operators are invariant under left translation. In particular,
"L^p-type" gradient estimates hold for p\in(1,\infty), and the p=2 gradient
estimate implies a Poincar\'e estimate in this context.Comment: 22 pages, 0 figures; final journal versio
Global Solvability of the Cauchy Problem for the Landau-Lifshitz-Gilbert Equation in Higher Dimensions
We prove existence, uniqueness and asymptotics of global smooth solutions for
the Landau-Lifshitz-Gilbert equation in dimension , valid under a
smallness condition of initial gradients in the norm. The argument is
based on the method of moving frames that produces a covariant complex
Ginzburg-Landau equation, and a priori estimates that we obtain by the method
of weighted-in-time norms as introduced by Fujita and Kato
Heat kernel analysis on semi-infinite Lie groups
This paper studies Brownian motion and heat kernel measure on a class of
infinite dimensional Lie groups. We prove a Cameron-Martin type
quasi-invariance theorem for the heat kernel measure and give estimates on the
norms of the Radon-Nikodym derivatives. We also prove that a logarithmic
Sobolev inequality holds in this setting.Comment: 35 page
Electrodynamic induction flowmeter
Device determines velocity and electrical conductivity of a moving fluid of high electrical resistance by imposing a transverse electro-quasistatic field on the fluid. Position changes of charge accumulations induced within the fluid by the field are sensed by relative movement between fluid and sensor
Synchronous charge-constrained electroquasistatic generator
Electroquasistatic generator depends on electroquasistatic interactions to provide synchronous operation. The generator employs a moving insulating belt, with an ac electric potential source to establish positively and negatively charged regions on the belt. The field effect of the charges on the belt creates an ac output voltage
Strong solvability of regularized stochastic Landau-Lifshitz-Gilbert equation
We examine a stochastic Landau-Lifshitz-Gilbert equation based on an exchange
energy functional containing second-order derivatives of the unknown field.
Such regularizations are featured in advanced micromagnetic models recently
introduced in connection with nanoscale topological solitons. We show that, in
contrast to the classical stochastic Landau-Lifshitz-Gilbert equation based on
the Dirichlet energy alone, the regularized equation is solvable in the
stochastically strong sense. As a consequence it preserves the topology of the
initial data, almost surely
Small Deviations for Time-Changed Brownian Motions and Applications to Second-Order Chaos
We prove strong small deviations results for Brownian motion under
independent time-changes satisfying their own asymptotic criteria. We then
apply these results to certain stochastic integrals which are elements of
second-order homogeneous chaos.Comment: 23 page
Flexual buckling of structural glass columns. Initial geometrical imperfection as a base for Monte Carlo simulation
In this paper Monte Carlo simulations of
structural glass columns are presented. The simulation
was performed according to the analytical second order
theory of compressed elastic rods. A previous research
on shape and size of initial geometrical imperfections is
briefly summarized. An experimental analysis of glass
columns that were performed for evaluation of equivalent
geometrical imperfections is mentioned too
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