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The automorphisms of convolution algebras of C∞ functions
Journal article   Open access   Peer reviewed

The automorphisms of convolution algebras of C∞ functions

Journal of mathematical analysis and applications, Vol.64(1), pp.25-47
1978
DOI: 10.1016/0022-247X(78)90018-5
url
https://doi.org/10.1016/0022-247X(78)90018-5View
Published (Version of record) Open Access

Abstract

We find the automorphisms and the spectra of several different topological convolution algebras of C ∞-functions on the real line. Starting with the convolution algebra of compactly supported C ∞-functions, equipped with the usual LF-topology, we define a corresponding convolution algebra of C ∞-functions of arbitrarily fast exponential decay at ∞; and convolution algebras of a given finite degree r of exponential decay at ∞. These algebras may be described topologically as “hyper Schwartz spaces.” With a natural Frechet topology, which we define, they get a structure as locally m-convex algebras. The continuous automorphisms and spectra of these algebras are described completely. We show that the algebra of C ∞-functions of infinitly fast exponential decay at ∞, H J , on the one hand, and the algebra of C ∞-functions of only a finite degree e −r¦x¦ decay at ∞, J r 0, on the other hand, have quite different automorphisms, although H J = ∩ r J r 0. As an application, we show that the conformal group is canonically represented as the full group of automorphisms of J r 0, and that this representation does not extend to a representation on the Banach algebra L 1( R ).

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