Lusternik--Schnirelmann theory on general spaces

Yu. B. Rudyak, F. Schlenk

We extend Lusternik-Schnirelmann theory to pairs $(f,\varphi )$, where $\varphi$ is a homotopy equivalence of a space $X$, $f$ is a function on $X$ which decreases along $\varphi$ and $(f,\varphi )$ satis…