# Homology, Homotopy and Applications

## Volume 7 (2005)

### Homotopy actions, cyclic maps and their duals

Pages: 169 – 184

DOI: https://dx.doi.org/10.4310/HHA.2005.v7.n1.a9

#### Authors

Martin Arkowitz (Department of Mathematics, Dartmouth College, Hanover, New Hampshire, U.S.A.)

Gregory Lupton (Department of Mathematics, Cleveland State University, Cleveland Ohio, U.S.A.)

#### Abstract

An action of $A$ on $X$ is a map $F \colon A \times X \to X$ such that $F\vert_X = \mathrm{id} \colon X \to X$. The restriction $F\vert_A \colon A \to X$ of an action is called a cyclic map. Special cases of these notions include group actions and the Gottlieb groups of a space, each of which has been studied extensively. We prove some general results about actions and their Eckmann-Hilton duals. For instance, we classify the actions on an $H$-space that are compatible with the $H$-structure. As a corollary, we prove that if any two actions $F$ and $F'$ of $A$ on $X$ have cyclic maps $f$ and $f'$ with $\Omega f = \Omega f'$, then $\Omega F$ and $\Omega F'$ give the same action of $\Omega A$ on $\Omega X$. We introduce a new notion of the category of a map $g$ and prove that $g$ is cocyclic if and only if the category is less than or equal to $1$. From this we conclude that if $g$ is cocyclic, then the Berstein-Ganea category of $g$ is $\le 1$. We also briefly discuss the relationship between a map being cyclic and its cocategory being $\le 1$.

#### Keywords

action, cyclic map, category of a map, coaction, cocyclic map, cocategory of a map

#### 2010 Mathematics Subject Classification

55M30, 55P30, 55Q05

Published 1 January 2005