Amenability of finite energy path and loop groups

Abstract

It is shown that the groups of finite energy (that is, Sobolev class $H^1$) paths and loops with values in a compact Lie group are amenable in the sense of Pierre de la Harpe, that is, every continuous action of such a group on a compact space admits an invariant regular Borel probability measure. To our knowledge, the strongest previously known result concerned the amenability of groups of continuous paths and loops (Malliavin and Malliavin 1992).

LaTeX, 19 pp., the final version sent to the journal upon acceptance. A remark added at the end of Preliminaries with two new citations, a missing sign added in the proof of Lemma 3.6, minor grammatical inaccuracies fixed