Lusternik--Schnirelman theory for closed 1-forms
Lusternik--Schnirelman theory for closed 1-forms
S. P. Novikov developed an analog of the Morse theory for closed 1-forms. In this paper we suggest an analog of the Lusternik–Schnirelman theory for closed 1-forms. For any cohomology class \xi\in H^1(M,\mathbf R) we define an integer \operatorname{cl}(\xi) ( the cup-length associated with \xi ); we prove that any …