arXiv subjects

Yong-Geun OH

Publications and source records attributed to Yong-Geun OH.

5 recordsLinked to original sources

arXiv2010

Seidel's long exact sequence on Calabi-Yau manifolds

In this paper, we generalize construction of Seidel's long exact sequence of Lagrangian Floer cohomology to that of compact Lagrangian submanifolds with vanishing Malsov class on general Calabi-Yau manifolds. We use the framework of anchored Lagrangian submanifolds developed in \cite{fooo:anchor} and some compactness theorem of \emph{smooth} $J$-holomorphic sections of Lefschetz Hamiltonian fibration for a generic choice of $J$. The proof of the latter compactness theorem involves a study of proper pseudoholomorphic curves in the setting of noncompact symplectic manifolds with cylindrical ends.

math.SG↗

arXiv2009

Unwrapped continuation invariance in Lagrangian Floer theory: energy and $C^0$ estimates

We consider pairs of Lagrangian submanifolds $(L_0,L), (L_1, L)$ belonging to the class of Lagrangian submanifolds with \emph{conic} ends on \emph{Weinstein manifolds}. The main purpose of the present paper is to define a canonical chain map $h_\CL: CF(L_0,L) \to CF(L_1,L)$ of Lagrangian Floer complex inducing an isomorphism in homology, under the Hamiltonian isotopy $\CL=\{L_s\}_{0 \leq s\leq 1}$ generated by \emph{conic} Hamiltonian functions such that the intersections $L \cap L_s$ do not escape to infinity. The main ingredients of the proof is an a priori bound for general isotopy of the energy \emph{quadratic} at infinity and a $C^0$-bound for the \emph{$C^1$-small} isotopy $\CL = \{L_s\}$, for the associated pseudo-holomorphic map equations with \emph{moving} Lagrangian boundary induced by a conic Hamiltonian isotopy. For the Lagrangian submanifolds with \emph{asymptotically conic} ends, we construct a natural homomorphism $h_\LL: HF(L_0,L) \to HF(L_1,L)$ for which the corresponding chain map may \emph{not} necessarily exist. This provides a more conventional construction of the chain isomorphism which replaces the sophisticated method using the Lagrangian cobordism via the machinery of \cite{kasturi-oh1,kasturi-oh2} whose details were only outlined in \cite{oh:gokova}.

math.SG↗

arXiv2009

The group of Hamiltonian homeomorphisms and continuous Hamiltonian flows

In this paper, we study the dynamical aspects of the \emph{Hamiltonian homeomorphism group} $Hameo(M,ω)$ which was introduced by Müller and the author. We introduce the notion of autonomous continuous Hamiltonian flows and extend the well-known conservation of energy to such flows. The definitions of the Hofer length and of the spectral invariants $ρ_a$ are extended to continuous Hamiltonian paths, and the Hofer norm and the spectral norm $γ:Ham(M,ω) \to \R_+$ are generalized to the corresponding intrinsic norms on $Hameo(M,ω)$ respectively. Using these extensions, we also extend the construction of Entov-Polterovich's Calabi quasi-morphism on $S^2$ to the space of continuous Hamiltonian paths. We also discuss a conjecture concerning extendability of Entov-Polterovich's quasi-morphism and its relation to the extendability of Calabi homomorphism on the disc to $Hameo(D^2,\del D^2)$, and their implication towards the simpleness question on the area preserving homeomorphism groups of the disc $D^2$ and of the sphere $S^2$.

math.SG↗

arXiv2009

Higher jet evaluation transversality of $J$-holomorphic curves

In this paper, we establish general stratawise higher jet evaluation transversality of $J$-holomorphic curves for a generic choice of almost complex structures $J$ tame to a given symplectic manifold $(M,ω)$. Using this transversality result, we prove that there exists a subset $\CJ_ω^{ram} \subset \CJ_ω$ of second category such that for every $J \in \CJ_ω^{ram}$, the dimension of the moduli space of (somewhere injective) $J$-holomorphic curves with a given ramification profile goes down by $2n$ or $2(n-1)$ depending on whether the ramification degree goes up by one or a new ramification point is created. We also derive that for each $J \in \CJ_ω^{ram}$ there are only a finite number of ramification profiles of $J$-holomorphic curves in a given homology class $β\in H_2(M;\Z)$ and provide an explicit upper bound on the number of ramification profiles in terms of $c_1(β)$ and the genus $g$ of the domain surface.

math.SG↗

arXiv2007

Floer mini-max theory, the Cerf diagram, and the spectral invariants

The author previously defined the spectral invariants, denoted by $ρ(H;a)$, of a Hamiltonian function $H$ as the mini-max value of the action functional $Å_H$ over the Novikov Floer cycles in the Floer homology class dual to the quantum cohomology class $a$. The spectrality axiom of the invariant $ρ(H;a)$ states that the mini-max value is a critical value of the action functional $Å_H$. The main purpose of the present paper is to prove this axiom for {\it nondegenerate} Hamiltonian functions in {\it irrational} symplectic manifolds $(M,ω)$. We also prove that the spectral invariant function $ρ_a: H \mapsto ρ(H;a)$ can be pushed down to a {\it continuous} function defined on the universal ({\it étale}) covering space $\widetilde{Ham}(M,ω)$ of the group $Ham(M,ω)$ of Hamiltonian diffeomorphisms on general $(M,ω)$. For a certain generic homotopy, which we call a {\it Cerf homotopy} $\HH = \{H^s\}_{0 \leq s\leq 1}$ of Hamiltonians, the function $ρ_a \circ \HH: s \mapsto ρ(H^s;a)$ is piecewise smooth away from a countable subset of $[0,1]$ for each non-zero quantum cohomology class $a$. The proof of this nondegenerate spectrality relies on several new ingredients in the chain level Floer theory, which have their own independent interest: a structure theorem on the Cerf bifurcation diagram of the critical values of the action functionals associated to a generic one-parameter family of Hamiltonian functions, a general structure theorem and the handle sliding lemma of Novikov Floer cycles over such a family and a {\it family version} of new transversality statements involving the Floer chain map, and many others. We call this chain level Floer theory as a whole the {\it Floer mini-max theory}.

math.SG↗