Momchil Konstantinov | Search arXiv

arXiv2020

Monotone Lagrangians in $\mathbb{CP}^n$ of minimal Maslov number $n+1$

We show that a monotone Lagrangian $L$ in $\mathbb{CP}^n$ of minimal Maslov number $n + 1$ is homeomorphic to a double quotient of a sphere, and thus homotopy equivalent to $\mathbb{RP}^n$. To prove this we use Zapolsky's canonical pearl complex for $L$ with coefficients in $\mathbb{Z}$, and various twisted versions thereof, where the twisting is determined by connected covers of $L$. The main tool is the action of the quantum cohomology of $\mathbb{CP}^n$ on the resulting Floer homologies.

math.SG↗

arXiv2017

Higher rank local systems in Lagrangian Floer theory

We extend Floer theory for monotone Lagrangians to allow coefficients in local systems of arbitrary rank. Unlike the rank 1 case, this is often obstructed by Maslov 2 discs. We study exactly what the obstruction is and define some natural unobstructed subcomplexes. To illustrate these constructions we do some explicit calculations for the Chiang Lagrangian $L_Δ \subseteq \mathbb{C}P^3$. For example, we equip $L_Δ$ with a particular rank 2 local system $W$ over the field with 2 elements such that the resulting Floer complex $CF^*(W,W)$ is unobstructed despite the presence of Maslov 2 discs. We compute that the cohomology $HF^*(W,W)$ is non-zero and deduce that the Chiang Lagrangian cannot be disjoined from $\mathbb{R}P^3$ by a Hamiltonian isotopy.

math.SG↗