# 101.820 VO (2std Vorlesung, Sommersemester 2019) AKNUM:Nichtlokale Operatoren - Analysis und NumerikTISS-Homepage

## Date and location

• First lecture: Thursday, 10.10.2019 14:00

Room: Freihaus Sem.R. DA grün 03 B (third floor green)

Lecture dates: Tuesday, 13:00-14:00, Thursday, 15:00-16:00

Room: Sem.R. DA grün 03C

On Thursday 07.11.2019 different room: Sem.R. DC rot 07

## Aim of the lecture

The aim of this lecture is to understand operator equations with non-local operators analytically and numerically.

## Subject of course

### What are non-local operators?

A non-local operator A (mapping between two function spaces) is characterized by the property that the evaluation of Af(x) does depend on the whole f and not only on values of f in a neighborhood of x. As various classical tools in analysis and numerics are not applicable to this class of operators, we introduce appropriate techniques for such problems.

### Examples of non-local operators

Differential operators such as the Laplacian Δ are local operators. However, integral operators such as the Fourier transform are non-local. In this lecture, we study integral operators of the form and integral equations Au = f analytically and numerically. More specific, we deal with (boundary) integral operators that arise from the representation formula of the Laplace equation as well as fractional differential operators for 0 < s < 1. Such operators appear naturally in more refined models of anomalous diffusion in physics, biology or finance. Mathematically, there are various definition of the fractional Laplacian, which are not equivalent on bounded domains. In this lecture, we will consider two different definitions - the spectral and integral fractional Laplacian - and discuss numerical methods for these two definitions.

## Lectures

#DateTopicLecturer
110.10.2019IntroductionFaustmann
215.10.2019Representation formulaFaustmann
317.10.2019Function spacesFaustmann
22.10.2019No lecture
24.10.2019No lecture
429.10.2019Conormal derivativeFaustmann
531.10.2019The Newton potentialFaustmann
65.11.2019The single layer potentialFaustmann
77.11.2019The Calderon systemFaustmann
812.11.2019Integral representationsFaustmann
914.11.2019Integral representationsFaustmann
19.11.2019No lecture

The lecture notes can be downloaded here as soon as they are written.
 12.11.2019 BEM-Skript Praetorius [pdf]

## Literature

W. McLean: Strongly elliptic systems and boundary integral equations Link

S. Sauter, C. Schwab: Boundary Element Methods Link

A. Bonito, J.P. Borthagaray, R.H. Nochetto, E. Otarola, A.J. Salgado: Numerical methods for fractional diffusion Link

## Required Knowledge

In principle, there is no specific previous knowledge required. However, basic knowledge in functional analysis, numerics and partial differential equations is helpful.

## Examination modalities

Oral examination, make an appointment by e-mail.