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Wolfgang Karcher

Publications and source records attributed to Wolfgang Karcher.

6 recordsLinked to original sources
arXiv2017

An Inverse Problem for Infinitely Divisible Moving Average Random Fields

Given a low frequency sample of an infinitely divisible moving average random field $\{\int_{\mathbb{R}^d} f(x-t)Λ(dx); \ t \in \mathbb{R}^d \}$ with a known simple function $f$, we study the problem of nonparametric estimation of the Lévy characteristics of the independently scattered random measure $Λ$. We provide three methods, a simple plug-in approach, a method based on Fourier transforms and an approach involving decompositions with respect to $L^2$-orthonormal bases, which allow to estimate the Lévy density of $Λ$. For these methods, the bounds for the $L^2$-error are given. Their numerical performance is compared in a simulation study.

math.ST↗
arXiv2011

Extrapolation of stable random fields

In this paper, we discuss three extrapolation methods for alpha-stable random fields with 1<alpha<=2. We justify them, giving proofs of the existence and uniqueness of the solutions for each method and providing sufficient conditions for path continuity. Two methods are based on minimizing the variability of the difference between the predictor and the theoretical value, whereas in the third approach we provide a new method that maximizes the covariation between these two quantities.

math.PR↗
arXiv2009

Simulation of infinitely divisible random fields

Two methods to approximate infinitely divisible random fields are presented. The methods are based on approximating the kernel function in the spectral representation of such fields, leading to numerical integration of the respective integrals. Error bounds for the approximation error are derived and the approximations are used to simulate certain classes of infinitely divisible random fields.

math.PR↗
arXiv2009

Derivation of an upper bound of the constant in the error bound for a near best m-term approximation

In the paper "The best m-term approximation and greedy algorithms" (V. N. Temlyakov), an error bound for a near best m-term approximation of a function g in L^p([0,1]^d) is provided, using a basis L^p-equivalent to the Haar system, where p is greater than one and less than infinity and d is a natural number. The bound includes a constant C(p) that is not given explicitly. The goal of this paper is to find an upper bound of the constant for the Haar system.

math.NA↗