We describe a method to improve both the accuracy and computational efficiency of a given finite difference scheme used to simulate a geophysical flow. The resulting modified scheme is at least as accurate as the original, has the same time step, and often uses the same spatial stencil. However, in certain parameter regimes it is higher order. As examples we apply the method to the shallow water equations, the Navier-Stokes equations, and to a sea breeze model.
We consider random Taylor series and the random $\dzeta$-functions. We prove non-continuation results for both, in case of independent random variables. Also, if the series defined by a stationary process can be continued beyond the radius of convergence we show that the process is deterministic.
Best constants are found for a class of multiplicative inequalities
that give an estimate of the C-norm of a function in terms of the product
of the L_2-norms of the powers of the Laplace operator.
Special attention is given to functions defined on the sphere S^n.
We show that the set of oscillatory motions in the Sitnikov restricted three body problem has full Hausdorff dimension. This is a joint work with V.Kaloshin.
We consider a nonlinear Schr\"odinger equation (NLS) with random
coefficients, in a regime of separation of scales corresponding to
diffusion approximation. The primary goal is to propose and
study an efficient numerical scheme in this framework. We use a
pseudo-spectral splitting scheme and we establish the order of the
global error. In particular we show that we can take an integration step
larger than the smallest scale of the problem, here the correlation
length of the random medium. We study
the asymptotic behavior of the numerical solution in the diffusion
approximation regime.
n this talk I discuss some principal problems in
Reconstructive Integral Geometry with emphasis on the X-ray transform
with recent results on range problems and inversion formulas.
All physical systems in equilibrium obey the laws of
thermodynamics. In other words, whatever the precise nature of the
interaction between the atoms and molecules at the microscopic level,
at the macroscopic level, physical systems exhibit universal behavior in
the sense that they are all governed by the same laws and formulae of
thermodynamics.
The speaker will recount some recent history of universality ideas in
physics starting with Wigner's model for the scattering of neutrons
off large nuclei and show how these ideas have led mathematicians to
investigate universal behavior for a variety of mathematical systems.
This is true not only for systems which have a physical origin, but also
for systems which arise in a purely mathematical context such as the
Riemann hypothesis, and a version of the card game solitaire called
patience sorting.