Equivariant means

Abstract

An $n$-mean (also called a ''topological social choice rule'') on a topological space $X$ is a continuous function $p:X^n\to X$ satisfying $p(x,\dots ,x)=x$ for every $x\in X$ and $p(x_1,\dots ,x_n)=p(x_{\sigma (1)},\dots x_{\sigma (n)})$ for any permutation $\sigma$ of $\{1,\dots ,n\}$. If, in addition, $X$ is a $G$-space and $p$ is equivariant with respect to the diagonal action of $G$ on $X^n$, we say that $p$ is an equivariant $n$-mean. In this paper, we continue the work initiated by H. Juárez-Anguiano about conditions on a $G$-space $X$, under which the existence of an equivariant $n$-mean guarantees that $X$ is a $G$-AR. We also explore this problem when we remove the symmetry condition on the definition of an $n$-mean.

19 pages