14,356 research outputs found
Fast and oblivious convolution quadrature
We give an algorithm to compute steps of a convolution quadrature
approximation to a continuous temporal convolution using only
multiplications and active memory. The method does not require
evaluations of the convolution kernel, but instead evaluations of
its Laplace transform, which is assumed sectorial.
The algorithm can be used for the stable numerical solution with
quasi-optimal complexity of linear and nonlinear integral and
integro-differential equations of convolution type. In a numerical example we
apply it to solve a subdiffusion equation with transparent boundary conditions
Time-Dependent Fluid-Structure Interaction
The problem of determining the manner in which an incoming acoustic wave is
scattered by an elastic body immersed in a fluid is one of central importance
in detecting and identifying submerged objects. The problem is generally
referred to as a fluid-structure interaction and is mathematically formulated
as a time-dependent transmission problem. In this paper, we consider a typical
fluid-structure interaction problem by using a coupling procedure which reduces
the problem to a nonlocal initial-boundary problem in the elastic body with a
system of integral equations on the interface between the domains occupied by
the elastic body and the fluid. We analyze this nonlocal problem by the Lubich
approach via the Laplace transform, an essential feature of which is that it
works directly on data in the time domain rather than in the transformed
domain. Our results may serve as a mathematical foundation for treating
time-dependent fluid-structure interaction problems by convolution quadrature
coupling of FEM and BEM
On an explicit representation of the solution of linear stochastic partial differential equations with delays
Based on the analysis of a certain class of linear operators on a Banach
space, we provide a closed form expression for the solutions of certain linear
partial differential equations with non-autonomous input, time delays and
stochastic terms, which takes the form of an infinite series expansion
A new numerical method for obtaining gluon distribution functions , from the proton structure function
An exact expression for the leading-order (LO) gluon distribution function
from the DGLAP evolution equation for the proton structure
function for deep inelastic scattering has
recently been obtained [M. M. Block, L. Durand and D. W. McKay, Phys. Rev.
D{\bf 79}, 014031, (2009)] for massless quarks, using Laplace transformation
techniques. Here, we develop a fast and accurate numerical inverse Laplace
transformation algorithm, required to invert the Laplace transforms needed to
evaluate , and compare it to the exact solution. We obtain accuracies
of less than 1 part in 1000 over the entire and spectrum. Since no
analytic Laplace inversion is possible for next-to-leading order (NLO) and
higher orders, this numerical algorithm will enable one to obtain accurate NLO
(and NNLO) gluon distributions, using only experimental measurements of
.Comment: 9 pages, 2 figure
- …