English

Augmentations and immersed Lagrangian fillings

Symplectic Geometry 2023-01-23 v2 Geometric Topology

Abstract

For a Legendrian link ΛJ1M\Lambda \subset J^1M with M=RM = \mathbb{R} or S1S^1, immersed exact Lagrangian fillings L\mboxSymp(J1M)T(R>0×M)L \subset \mbox{Symp}(J^1M) \cong T^*(\mathbb{R}_{>0} \times M) of Λ\Lambda can be lifted to conical Legendrian fillings ΣJ1(R>0×M)\Sigma \subset J^1(\mathbb{R}_{>0} \times M) of Λ\Lambda. When Σ\Sigma is embedded, using the version of functoriality for Legendrian contact homology (LCH) from [30], for each augmentation α:A(Σ)Z/2\alpha: \mathcal{A}(\Sigma) \rightarrow \mathbb{Z}/2 of the LCH algebra of Σ\Sigma, there is an induced augmentation ϵ(Σ,α):A(Λ)Z/2\epsilon_{(\Sigma,\alpha)}: \mathcal{A}(\Lambda) \rightarrow \mathbb{Z}/2. With Σ\Sigma fixed, the set of homotopy classes of all such induced augmentations, IΣAug(Λ)/I_\Sigma \subset \mathit{Aug}(\Lambda)/{\sim}, is a Legendrian isotopy invariant of Σ\Sigma. We establish methods to compute IΣI_\Sigma based on the correspondence between Morse complex families and augmentations. This includes developing a functoriality for the cellular DGA from [31] with respect to Legendrian cobordisms, and proving its equivalence to the functoriality for LCH. For arbitrary n1n \geq 1, we give examples of Legendrian torus knots with 2n2n distinct conical Legendrian fillings distinguished by their induced augmentation sets. We prove that when ρ1\rho \neq 1 and ΛJ1R\Lambda \subset J^1\mathbb{R} every ρ\rho-graded augmentation of Λ\Lambda can be induced in this manner by an immersed Lagrangian filling. Alternatively, this is viewed as a computation of cobordism classes for an appropriate notion of ρ\rho-graded augmented Legendrian cobordism.

Keywords

Cite

@article{arxiv.2006.16436,
  title  = {Augmentations and immersed Lagrangian fillings},
  author = {Yu Pan and Dan Rutherford},
  journal= {arXiv preprint arXiv:2006.16436},
  year   = {2023}
}

Comments

51 pages, 22 figures. Accepted version to appear in Journal of Topology. Version 2 is shorter than Version 1 with more efficient exposition. In places, readers desiring more details are referred to Version 1

R2 v1 2026-06-23T16:43:09.890Z