Lagrangian concordance is not a partial order in high dimensions

Abstract

In this short note we provide the examples of pairs of closed, connected Legendrian non-isotopic Legendrian submanifolds $(\hat{I}{›}_{-},\hat{I}{›}_{+})$ of the $(4n+1)$-dimensional contact vector space, $n>1$, such that there exist Lagrangian concordances from $\hat{I}{›}_{-}$ to $\hat{I}{›}_{+}$ and from $\hat{I}{›}_{+}$ to $\hat{I}{›}_{-}$. This contradicts anti-symmetry of the Lagrangian concordance relation, and, in particular, implies that Lagrangian concordances with connected Legendrian ends do not define a partial order in high dimensions. In addition, we explain how to get the same result for the relation given by exact Lagrangian cobordisms with connected Legendrian ends in the $(2n+1)$-dimensional contact vector space, $n>1$.

5 pages, 1 figure; updated version, accepted for publication in Pacific Journal of Mathematics