International Journal of Mathematics and Mathematical Sciences
Volume 23 (2000), Issue 12, Pages 827-831

Spatial numerical ranges of elements of subalgebras of C0(X)

Sin-Ei Takahasi

Department of Basic Technology, Applied Mathematics and Physics, Yamagata University, Yonezawa 992-8510, Japan

Received 9 July 1998; Revised 26 January 1999

Copyright © 2000 Sin-Ei Takahasi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


When A is a subalgebra of the commutative Banach algebra C0(X) of all continuous complex-valued functions on a locally compact Hausdorff space X, the spatial numerical range of element of A can be described in terms of positive measures.