FIRST DESCRIPTION OF ESSENTIAL SPECTRUM

WEYL, HERMANN.

Über gewöhnliche Differentialgleichungen mit Singularitäten und die zugehörigen Entwicklungen willkürlicher Funktionen.

Leipzig, B.G. Teubner, 1910. 8vo. Without wrappers. Extracted from "Mathematische Annalen. Begründet 1868 durch Alfred Clebsch und Carl Neumann. 68. Band". Pp. 220-69.

First printing of Weyl's important paper in which he created the topic of essential spectrum.
In mathematics, the essential spectrum is a certain subset of its spectrum, defined by a condition of the type that says, "fails badly to be invertible".

Order-nr.: 49486