6,066 research outputs found
Boundary integral equation methods for the elastic and thermoelastic waves in three dimensions
In this paper, we consider the boundary integral equation (BIE) method for
solving the exterior Neumann boundary value problems of elastic and
thermoelastic waves in three dimensions based on the Fredholm integral
equations of the first kind. The innovative contribution of this work lies in
the proposal of the new regularized formulations for the hyper-singular
boundary integral operators (BIO) associated with the time-harmonic elastic and
thermoelastic wave equations. With the help of the new regularized
formulations, we only need to compute the integrals with weak singularities at
most in the corresponding variational forms of the boundary integral equations.
The accuracy of the regularized formulations is demonstrated through numerical
examples using the Galerkin boundary element method (BEM).Comment: 24 pages, 6 figure
Stationary Distributions for Retarded Stochastic Differential Equations without Dissipativity
Retarded stochastic differential equations (SDEs) constitute a large
collection of systems arising in various real-life applications. Most of the
existing results make crucial use of dissipative conditions. Dealing with "pure
delay" systems in which both the drift and the diffusion coefficients depend
only on the arguments with delays, the existing results become not applicable.
This work uses a variation-of-constants formula to overcome the difficulties
due to the lack of the information at the current time. This paper establishes
existence and uniqueness of stationary distributions for retarded SDEs that
need not satisfy dissipative conditions. The retarded SDEs considered in this
paper also cover SDEs of neutral type and SDEs driven by L\'{e}vy processes
that might not admit finite second moments.Comment: page 2
Exponential Mixing for Retarded Stochastic Differential Equations
In this paper, we discuss exponential mixing property for Markovian
semigroups generated by segment processes associated with several class of
retarded Stochastic Differential Equations (SDEs) which cover SDEs with
constant/variable/distributed time-lags. In particular, we investigate the
exponential mixing property for (a) non-autonomous retarded SDEs by the
Arzel\`{a}--Ascoli tightness characterization of the space \C equipped with
the uniform topology (b) neutral SDEs with continuous sample paths by a
generalized Razumikhin-type argument and a stability-in-distribution approach
and (c) jump-diffusion retarded SDEs by the Kurtz criterion of tightness for
the space \D endowed with the Skorohod topology.Comment: 20 page
Error estimates of numerical methods for the nonlinear Dirac equation in the nonrelativistic limit regime
We present several numerical methods and establish their error estimates for
the discretization of the nonlinear Dirac equation in the nonrelativistic limit
regime, involving a small dimensionless parameter which is
inversely proportional to the speed of light. In this limit regime, the
solution is highly oscillatory in time, i.e. there are propagating waves with
wavelength and in time and space, respectively. We
begin with the conservative Crank-Nicolson finite difference (CNFD) method and
establish rigorously its error estimate which depends explicitly on the mesh
size and time step as well as the small parameter . Based on the error bound, in order to obtain `correct' numerical solutions
in the nonrelativistic limit regime, i.e. , the CNFD method
requests the -scalability: and
. Then we propose and analyze two numerical methods
for the discretization of the nonlinear Dirac equation by using the Fourier
spectral discretization for spatial derivatives combined with the exponential
wave integrator and time-splitting technique for temporal derivatives,
respectively. Rigorous error bounds for the two numerical methods show that
their -scalability is improved to and
when compared with the CNFD method. Extensive
numerical results are reported to confirm our error estimates.Comment: 35 pages. 1 figure. arXiv admin note: substantial text overlap with
arXiv:1504.0288
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