Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-16T15:01:25.626Z Has data issue: false hasContentIssue false

On Extending the Trace as a Linear Functional, II

Published online by Cambridge University Press:  20 November 2018

George A. Elliott*
Affiliation:
University of Copenhagen, Copenhagen, Denmark
Rights & Permissions [Opens in a new window]

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

A positive bounded selfadjoint operator is in the trace class of von Neumann and Schatten ([4]) if the sum of its diagonal matrix elements with respect to some orthonormal basis is finite, and the trace is then defined to be this sum, which is independent of the basis. A bounded selfadjoint but not necessarily positive operator x is in the trace class if in the decomposition x = x+ – x, with x+ and x positive and x+x = 0, both x+ and xare in the trace class; the trace of x is then defined to be the difference of the finite traces of x+ and x. The trace defined in this way is a linear functional on the trace class, and is unitarily invariant; if u is a unitary operator, the trace of uxu−1 is the same as the trace of x.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1980

References

1. Elliott, G. A., On extending the trace as a linear functional, Rep. Math. Phys. 15 (1979), 199203.Google Scholar
2. Lundberg, L.-E., Quasi-free “second quantization”, Comm. Math. Phys. 50 (1976), 103112.Google Scholar
3. Lundberg, L.-E., Vacuum polarization due to potential perturbations, preprint, University of Copenhagen (1977).Google Scholar
4. Schatten, R. and von Neumann, J., The cross-space of linear transformations II, Ann. of Math. 47 (1946), 608630.Google Scholar
5. von Neumann, J., Charakterisierung des Spektrums eines Integraloperators, Actualités Sci. Indust., no. 229 (Hermann, Paris, 1935).Google Scholar
6. Weiss, G., The Fuglede commutativity theorem modulo the Hilbert-Schmidt class and generating functions for matrix operators I, Trans. Amer. Math. Soc. 246 (1978), 193209.Google Scholar