arXiv subjects

Mei-Lin Yau

Publications and source records attributed to Mei-Lin Yau.

10 recordsLinked to original sources

arXiv2022

Special Hamiltonian $S^1$-actions on symplectic 4-manifolds

In this paper we consider symplectic 4-manifolds $(M,\omega)$ with $c_1(M,\omega)=0$ which admit a Hamiltonian $S^1$-action together with an equivariant Maslov condition on orbits of the group action. We call such spaces {\em special Hamiltonian $S^1$-spaces}. It turns out that there are no compact special Hamiltonian $S^1$-spaces. We classify all exact special Hamiltonian $S^1$-spaces and show that all of them admit the structure of a Stein surface.

math.SG↗

arXiv2016

Isotropic tori in $\mathbb{C}^m$ revisited

We show that for $m>n\geq 2$, there are at least two exact isotropic $n$-tori in $\mathbb{C}^m$ which are not Hamiltonian isotopic in $\mathbb{C}^m$, even though they are smoothly isotopic as isotropic $n$-tori. We apply this discovery to obtain more distinct non-exact isotropic tori in $\mathbb{C}^m$.

math.SG↗

arXiv2016

Exact Lagrangian tori in $T^*\mathbb{T}^n$

We show that for $n\geq 2$ there exists an exact Lagrangian submanifold $L$ in the cotangent bundle $T^*\mathbb{T}^n$ of the $n$-dimensional torus $\mathbb{T}^n$ such that $L$ is symplectically but not Hamiltonian isotopic to the zero section of $T^*\mathbb{T}^n$.

math.SG↗

arXiv2013

Surgery and Invariants of Lagrangian Surfaces

We considered a surgery, called Lagrangian attaching disk surgery, that can be applied to a Lagrangian surface L at the presence of a Lagrangian attaching disk D, to obtain a new Lagrangian surface L' which is always smoothly isotopic to L. We showed that this type of surgery includes all even generalized Dehn twists as constructed by Paul Seidel. We also constructed a new symplectic invariant, called y-index, for orientable closed Lagrangian surfaces immersed in a parallelizable symplectic 4-manifold W. With y-index we proved that L and L' are not Hamiltonian isotopic. We also obtained new examples of nullhomologous Lagrangian tori which are smooth isotopic but not Hamiltonian isotopic.

math.SG↗

arXiv2011

Monodromy groups of Lagrangian tori in the symplectic 4-space

We determine the Lagrangian monodromy group L(T) and the smooth monodromy group S(T) of a Clifford torus T in the symplectic 4-space. We show that L(T) is isomorphic to the infinite dihedral group, and S(T) is generated by three reflections. We give explicit formulas for both groups. We also show that if a Lagrangian torus is smoothly isotopic to a Clifford torus then the smooth isotopy can be chosen to be Lagrangian outside of a disc.

math.SG↗

arXiv2009

Monodromy and isotopy of monotone Lagrangian tori

We define new Hamiltonian isotopy invariants for a monotone Lagrangian torus embedded in a symplectic 4-manifold. We show that, in the standard symplectic 4-space, these invariants distinguish a monotone Clifford torus from a Chekanov torus.

math.SG↗

arXiv2005

A Holomorphic 0-Surgery Model for Open Books with Application to Cylindrical Contact Homology

We give a simple model in the complex plane of the 0-surgery along a fibered knot of a closed 3-manifold M to yield a mapping torus M'. This model allows explicit relations between pseudoholomorphic curves in the symplectizations of M and M'. As an application we use it to compute the cylindrical contact homology of open books resulting from a positive Dehn twist on a torus with boundary.

math.SG↗

arXiv2005

Vanishing of the contact homology of overtwisted contact 3--manifolds

We give a proof of, for the case of contact structures defined by global contact 1-forms, a Theorem stated by Eliashberg that for any overtwisted contact structure on a closed 3-manifold, its contact homology is 0. A different proof is also outlined in the appendix by Yakov Eliashberg.

math.SG↗

arXiv2004

Invariants of Lagrangian surfaces

We define a nonnegative integer $\la(L,L_0;ϕ)$ for a pair of diffeomorphic closed Lagrangian surfaces $L_0,L$ embedded in a symplectic 4-manifold $(M,\w)$ and a diffeomorphism $ϕ\in\Diff^+(M)$ satisfying $ϕ(L_0)=L$. We prove that if there exists $ϕ\in\Diff^+_o(M)$ with $ϕ(L_0)=L$ and $\la(L,L_0;ϕ)=0$, then $L_0,L$ are symplectomorphic. We also define a second invariant $n(L_1,L_0;[L_t])=n(L_1,L_0,[ϕ_t])$ for a smooth isotopy $L_t=ϕ_t(L_0)$ between two Lagrangian surfaces $L_0$ and $L_1$ with $\la (L_1,L_0;ϕ_1)=0$, which serves as an obstruction of deforming $L_t$ to a Lagrangian isotopy with $L_0,L_1$ preserved.

math.SG↗

arXiv2004

Cylindrical contact homology of subcritical Stein-fillable contact manifolds

We use contact handle decompositions and a stabilization process to compute the cylindrical contact homology of a subcritical Stein-fillable contact manifold with vanishing first Chern class, and show that it is completely determined by the homology of a subcritical Stein-filling of the contact manifold.

math.SG↗