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Yong-Geun Oh

Publications and source records attributed to Yong-Geun Oh.

At least 73 records · Page 4Linked to original sources
arXiv2016

Lagrangian Floer theory and mirror symmetry on compact toric manifolds

In this paper we study Lagrangian Floer theory on toric manifolds from the point of view of mirror symmetry. We construct a natural isomorphism between the Frobenius manifold structures of the (big) quantum cohomology of the toric manifold and of Saito's theory of singularities of the potential function constructed in \cite{fooo09} via the Floer cohomology deformed by ambient cycles. Our proof of the isomorphism involves the open-closed Gromov-Witten theory of one-loop.

math.SG↗
arXiv2016

Anti-symplectic involution and Floer cohomology

The main purpose of the present paper is a study of orientations of the moduli spaces of pseudo-holomorphic discs with boundary lying on a \emph{real} Lagrangian submanifold, i.e., the fixed point set of an anti-symplectic involutions $τ$ on a symplectic manifold. We introduce the notion of $τ$-relatively spin structure for an anti-symplectic involution $τ$, and study how the orientations on the moduli space behave under the involution $τ$. We also apply this to the study of Lagrangian Floer theory of real Lagrangian submanifolds. In particular, we study unobstructedness of the $τ$-fixed point set of symplectic manifolds and in particular prove its unobstructedness in the case of Calabi-Yau manifolds. And we also do explicit calculation of Floer cohomology of $\R P^{2n+1}$ over $Λ_{0,nov}^{\Z}$ which provides an example whose Floer cohomology is not isomorphic to its classical cohomology. We study Floer cohomology of the diagonal of the square of a symplectic manifold, which leads to a rigorous construction of the quantum Massey product of symplectic manifold in complete generality.

math.SG↗
arXiv2015

Continuous Hamiltonian dynamics and area-preserving homeomorphism group of $D^2$

The main purpose of this paper is to propose a scheme of a proof of the nonsimpleness of the group $Homeo^Ω(D^2,\partial D^2)$ of area preserving homeomorphisms of the 2-disc $D^2$. We first establish the existence of Alexander isotopy in the category of Hamiltonian homeomorphisms. This reduces the question of extendability of the well-known Calabi homomorphism ${\rm Cal}:Diff^Ω(D^1,\partial D^2) \to \mathbb R$ to a homomorphism $\overline{\rm Cal}:Hameo(D^2,\partial D^2) \to \mathbb R$ to that of the vanishing of the basic phase function $f_{\underline{\mathbb F}}$, a Floer theoretic graph selector previously constructed by the author, that is associated to the graph of the topological Hamiltonian loop and its normalized Hamiltonian $\underline{F}$ on $S^2$ that is obtained via the natural embedding $D^2 \hookrightarrow S^2$. Here $Hameo(D^2,\partial D^2)$ is the group of Hamiltonian homeomorphisms introduced by Müller and the author. We then provide an evidence of this vanishing conjecture by proving the conjecture for the special class of \emph{weakly graphical} topological Hamiltonian loops on $D^2$ via a study of the associated Hamilton-Jacobi equation.

math.SG↗
arXiv2015

Shrinking good coordinate systems associated to Kuranishi structures

The notion of good coordinate system was introduced by Fukaya and Ono in [FOn] in their construction of virtual fundamental chain via Kuranishi structure which was also introduced therein. This notion was further clarified in [FOOO1] in some detail. In those papers no explicit ambient space was used and hence the process of gluing local Kuranishi charts in the given good coordinate system was not discussed there. In our more recent writing [FOOO2, FOOO3] we use an ambient space obtained by gluing the Kuranishi charts. In this note we prove in detail that we can always shrink the given good coordinate system so that the resulting `ambient space' becomes Hausdorff. This note is self-contained and uses only standard facts in general topology.

math.SG↗
arXiv2015

Kuranishi structure, Pseudo-holomorphic curve, and Virtual fundamental chain: Part 1

This is the first part of the article we promised at the end of [FOOO13, Section 1]. We discuss the foundation of the virtual fundamental chain and cycle technique, especially its version appeared in [FOn] and also in [FOOO4, Section A1, Section 7.5], [FOOO7, Section 12], [Fu2]. In Part 1, we focus on the construction of the virtual fundamental chain on a single space with Kuranishi structure. We mainly discuss the de Rham version and so work over $\mathbb R$-coefficients, but we also include a self-contained account of the way how to work over $\mathbb Q$-coefficients in case the dimension of the space with Kuranishi structure is $\le 1$. Part 1 of this document is independent of our earlier writing [FOOO13]. We also do not assume the reader have any knowledge on the pseudo-holomorphic curve, in Part 1. Part 2 (resp. Part 3), which will appear in the near future, discusses the case of a system of Kuranishi structures and its simultaneous perturbations (resp. the way to implement the abstract story in the study of moduli spaces of pseudo-holomorphic curves).

math.SG↗
arXiv2013

Lagrangian Floer theory over integers: spherically positive symplectic manifolds

In this paper we study the Lagrangian Floer theory over $\Z$ or $\Z_2$. Under an appropriate assumption on ambient symplectic manifold, we show that the whole story of Lagrangian Floer theory in \cite{fooo-book} can be developed over $\Z_2$ coefficients, and over $\Z$ coefficients when Lagrangian submanifolds are relatively spin. The main technical tools used for the construction are the notion of the sheaf of groups, and stratification and compatibility of the normal cones applied to the Kuranishi structure of the moduli space of pseudo-holomorphic discs.

math.SG↗
arXiv2013

Geometry of generating functions and Lagrangian spectral invariants

Partially motivated by the study of topological Hamiltonian dynamics, we prove various $C^0$-aspects of the Lagrangian spectral invariants and the basic phase functions $f_H$, that is, a natural graph selector constructed by Lagrangian Floer homology of $H$ (relative to the zero section $o_N$). In particular, we prove that $$ γ^{lag}(ϕ_H^1(o_N)): = ρ^{lag}(H;1) - ρ^{lag}(H;[pt]^\#) \to 0 $$ as $ϕ_H^1 \to id$, \emph{provided} $H$'s satisfy $\supp X_H \subset D^R(T^*N) \setminus o_B$ for some $R > 0$ and a closed subset $B \subset N$ with nonempty interior. We also study the relationship between $f_H$ and $ρ^{lag}(H;1)$ and prove a structure theorem of the micro-support of the singular locus $\Sing(σ_H)$ of the function $f_H$. Based on this structure theorem and a classification theorem of generic Lagrangian singularity in $\dim N = 2$ obtained by Arnold's school, we define the notion of cliff-wall surgery when $\dim N = 2$: the surgery replaces a multi-valued Lagrangian graph $ϕ_H^1(o_N)$ by a piecewise-smooth Lagrangian cycle that is canonically constructed out of the single valued branch $Σ_H: = \Graph df_H \subset ϕ_H^1(o_N)$ defined on an open dense subset of $N \setminus \Sing(σ_H)$ of codimension 1.

math.SG↗
arXiv2013

Localization of Floer homology of engulfable topological Hamiltonian loop

Localization of Floer homology is first introduced by Floer \cite{floer:fixed} in the context of Hamiltonian Floer homology. The author employed the notion in the Lagrangian context for the pair $(ϕ_H^1(L),L)$ of compact Lagrangian submanifolds in tame symplectic manifolds $(M,ω)$ in \cite{oh:newton,oh:imrn} for a compact Lagrangian submanifold $L$ and $C^2$-small Hamiltonian $H$. In this article, motivated by the study of topological Hamiltonian dynamics, we extend the localization process for any engulfable Hamiltonian path $ϕ_H$ whose time-one map $ϕ_H^1$ is sufficiently $C^0$-close to the identity (and also to the case of triangle product), and prove that the value of local Lagrangian spectral invariant is the same as that of global one. Such a Hamiltonian path naturally occurs as an approximating sequence of engulfable topological Hamiltonian loop. We also apply this localization to the graphs $\Graph ϕ_H^t$ in $(M\times M, ω\oplus -ω)$ and localize the Hamiltonian Floer complex of such a Hamiltonian $H$. We expect that this study will play an important role in the study of homotopy invariance of the spectral invariants of topological Hamiltonian.

math.SG↗
arXiv2012

Technical details on Kuranishi structure and virtual fundamental chain

This is an expository article on the theory of Kuranishi structure and is based on a series of pdf files we uploaded for the discussion of the google group named `Kuranishi' (with its administrator H. Hofer). There we replied to several questions concerning Kuranishi structure raised by K. Wehrheim. At this stage we submit this article to the e-print arXiv, all the questions or objections asked in that google group were answered, supplemented or confuted by us. We first discuss the abstract theory of Kuranishi structure and virtual fundamental chain/cycle. This part can be read independently from other parts. We then describe the construction of Kuranishi structure on the moduli space of pseudoholomorphic curves, including the complete analytic detail of the gluing construction as well as the smoothness of the resulting Kuranishi structure. The case of S^1 equivariant Kuranishi structure which appears in the study of time independent Hamiltonian and the moduli space of Floer's equation is included.

math.SG↗
arXiv2012

Deformations of coisotropic submanifolds in locally conformal symplectic manifolds

In this paper, we study deformations of coisotropic submanifolds in a locally conformal symplectic manifold. Firstly, we derive the equation that governs $C^\infty$ deformations of coisotropic submanifolds and define the corresponding $C^\infty$-moduli space of coisotropic submanifolds modulo the Hamiltonian isotopies. Secondly, we prove that the formal deformation problem is governed by an $L_\infty$-structure which is a $\frak b$-deformation of strong homotopy Lie algebroids introduced in Oh and Park (2005) in the symplectic context. Then we study deformations of locally conformal symplectic structures and their moduli space, and the corresponding bulk deformations of coisotropic submanifolds. Finally we revisit Zambon's obstructed infinitesimal deformation (Zambon, 2002) in this enlarged context and prove that it is still obstructed.

math.SG↗
arXiv2011

A compactification of the space of maps from curves

We construct a new compactification of the moduli space of maps from pointed nonsingular projective stable curves to a nonsingular projective variety with prescribed ramification indices at the points. It is shown to be a proper Deligne-Mumford stack equipped with a natural virtual fundamental class.

math.AG↗
arXiv2011

Displacement of polydisks and Lagrangian Floer theory

There are two purposes of the present article. One is to correct an error in the proof of Theorem 6.1.25 in \cite{fooo:book}, from which Theorem J \cite{fooo:book} follows. In the course of doing so, we also obtain a new lower bound of the displacement energy of polydisks in general dimension. The results of the present article are motivated by the recent preprint of Hind \cite{hind} where the 4 dimensional case is studied. Our proof is different from Hind's even in the 4 dimensional case and provides stronger result, and relies on the study of torsion thresholds of Floer cohomology of Lagrangian torus fiber in simple toric manifolds associated to the polydisks.

math.SG↗