arXiv subjects

Samuel T. Lisi

Publications and source records attributed to Samuel T. Lisi.

4 recordsLinked to original sources

arXiv2019

Symplectic Homology of complements of smooth divisors

If $(X, ω)$ is a symplectic manifold, and $Σ$ is a smooth symplectic submanifold Poincaré dual to a positive multiple of $ω$, $X \setminus Σ$ admits a compactification as a Liouville domain, which we then complete to $(W, dλ)$. Under monotonicity assumptions on $X$ and on $Σ$, we construct a chain complex whose homology computes the Symplectic Homology of $W$. We show the differential is given in terms of Morse contributions, terms computed from Gromov-Witten invariants of $X$ relative to $Σ$ and terms computed from the Gromov-Witten invariants of $Σ$. We use a Morse-Bott model for symplectic homology. Our proof involves comparing Floer cylinders with punctures to pseudoholomorphic curves in in the symplectization of the unit normal bundle to $Σ$.

math.SG↗

arXiv2018

Morse-Bott Split Symplectic Homology

We introduce a chain complex associated to a Liouville domain $(\overline{W}, dλ)$ whose boundary $Y$ admits a Boothby--Wang contact form (i.e. is a prequantization space). The differential counts cascades of Floer solutions in the completion $W$ of $\overline{W}$, in the spirit of Morse--Bott homology (as in work of Bourgeois, Frauenfelder arXiv:math/0309373 and Bourgeois-Oancea arXiv:0704.1039). The homology of this complex is the symplectic homology of the completion $W$. We identify a class of simple cascades and show that their moduli spaces are cut out transversely for generic choice of auxiliary data. If $X$ is obtained by collapsing the boundary along Reeb orbits and $Σ$ is the quotient of $Y$ by the $S^1$-action induced by the Reeb flow, we also establish transversality for certain moduli spaces of holomorphic spheres in $X$ and in $Σ$. Finally, under monotonicity assumptions on $X$ and $Σ$, we show that for generic data, the differential in our chain complex counts elements of moduli spaces that are transverse. Furthermore, by some index estimates, we show that very few combinatorial types of cascades can appear in the differential.

math.SG↗

arXiv2010

Dividing sets as nodal sets of an eigenfunction of the Laplacian

We show that for any convex surface S in a contact 3-manifold, there exists a metric on S and a neighbourhood contact isotopic to $S \times I$ with contact structure given as $\ker(ud - \star du)$ where u is an eigenfunction of the Laplacian on S, and $\star$ is the Hodge star from the metric on $S$. This answers a question posed by Komendarczyk.

math.SG↗

arXiv2007

Homoclinic Orbits and Lagrangian Embeddings

This paper introduces techniques of symplectic topology to the study of homoclinic orbits in Hamiltonian systems. The main result is a strong generalization of homoclinic existence results due to Sere and to Coti-Zelati, Ekeland and Sere, which were obtained by variational methods. Our existence result uses a modification of a construction due to Mohnke (originally in the context of Legendrian chords), and an energy--capacity inequality of Chekanov. In essence, we show the existence of a homoclinic orbit by showing a certain Lagrangian embedding cannot exist. We consider a (possibly time dependent) Hamiltonian system on an exact symplectic manifold (W, ω= d λ) with a hyperbolic rest point. In the case of periodic time dependence, we show the existence of an orbit homoclinic to the rest point if λ(X_H) - H is positive and proper, H is positive outside a compact set and proper, and (W, ω) admits the structure of a Weinstein domain. In the autonomous case, we establish the existence of an orbit homoclinic to the rest point if the critical level is of restricted contact-type, and the critical level has a Hamiltonian displaceable neighbourhood.

math.SG↗