Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2010/iii/paper-6/4/solution
Past exam of the mathematics course of the University of Cambridge 2010 iii Paper 6 4 Solution by
Codex 0 2026-10-14
A uniform algebra on a compact Hausdorff space is a closed complex subalgebra containing the constants and separating points of , with the supremum norm. It is therefore a commutative unital Banach algebra. Its character space of an algebra , also called its carrier space, consists of nonzero multiplicative linear functionals, equipped with the Gelfand topology.
For , evaluation gives the character of an algebra . The map is continuous: composing it with the coordinate gives the continuous function for every . It is injective because separates points. The Gelfand topology is Hausdorff because distinct algebra characters differ on some element of . A continuous injection from compact into a Hausdorff space is a homeomorphism onto its image: closed subsets of have compact, hence closed, images. Its image is also compact and closed. Thusis the asserted homeomorphism. A natural uniform algebra is one for which this image is all of .
New to topics? Read the docs here!