Bordism classes of loops and Floer’s equation in cotangent bundles

Abstract

For each representative \(\mathfrak {B}\) of a bordism class in the free loop space of a manifold, we associate a moduli space of finite length Floer cylinders in the cotangent bundle. The left end of the Floer cylinder is required to be a lift of one of the loops in \(\mathfrak {B}\), and the right end is required to lie on the zero section. Under certain assumptions on the Hamiltonian functions, the length of the Floer cylinder is a smooth proper function, and evaluating the level sets at the right end produces a family of loops cobordant to \(\mathfrak {B}\). The argument produces arbitrarily long Floer cylinders with certain properties. We apply this to prove an existence result for 1-periodic orbits of certain Hamiltonian systems in cotangent bundles, and also to estimate the relative Gromov width of starshaped domains in certain cotangent bundles. The moduli space is similar to moduli spaces considered in Abouzaid (J Symp Geom 10(1):27–79, 2012), Abbondandolo and Figalli (J Differ Equ 234:626–653, 2007) and Abbondandolo and Schwarz (Geom Topol 14:1569–1722, 2010) for Tonelli Hamiltonians. The Hamiltonians we consider are not Tonelli, but rather of “contact-type” in the symplectization end.