*Wissenschaftliches Programm* *Liste der Vortragenden*

**Sektion 2**

Montag, 18.09.2000,
15.30–15.50 Uhr, POT 51

#### Christiane Tretter, Universität Regensburg, NWF I - Mathematik

We study a system of singular differential equations which arises in a physical model describing the
oscillations of a plasma in an equilibrium configuration in a cylindrical domain. The main
result is a description of the essential spectrum of this problem as the spectrum of certain
multiplication operators. It turns out that in contrast with the so-called hard core problem
(where the differential equations are not singular) new intervals of essential spectrum may
appear which can be expressed in terms of the asymptotic Hain–Lüst operator. A main tool
here is a lemma about the essential spectrum of certain pseudo-differential operators. We
also discuss the location of the various parts of the essential spectrum and the question of
stability.

(Joint work with R. Mennicken, S. Naboko)