arXiv subjects

Jaeyoo Choy

Publications and source records attributed to Jaeyoo Choy.

9 recordsLinked to original sources

arXiv2018

The $SO(3)$-instanton moduli space and tensor products of ADHM data

Let $M^K_n$ be the moduli space of framed $K$-instantons with instanton number $n$ when $K$ is a compact simple Lie group of classical type. Due to Donaldson's theorem, its scheme structure is given by the regular locus of a GIT quotient of $μ^{-1}(0)$ where $μ$ is the moment map on the associated symplectic vector space of ADHM data. A main theorem of this paper asserts that $μ$ is flat for $K=SO(3,\mathbb{R})$ and any $n\ge0$. Hence we complete the interpretation of the K-theoretic Nekrasov partition function for the classical groups in Nekrasov-Shadchin's work in term of Hilbert series of the instanton moduli spaces together with the author's previous results. We also write ADHM data for the second symmetric and exterior products of the associated vector bundle of an instanton. This gives an explicit quiver-theoretic description of the isomorphism $M^{K}_{n}\cong M^{K'}_{n}$ for all the pairs $K,K'$ with isomorphic Lie algebras.

math.AG↗

arXiv2018

Dynamics of riemannian 1-foliations on $3$-manifolds

In this paper we study several dynamical properties of the riemannian $1$-dimensional foliation $\mathcal{L}$ on an oriented closed 3-manifold $M$. Carriere classified such pairs $(M,\mathcal{L})$. Using the classification we prove the nonhyperbolicity of $(M,\mathcal{L})$. Also we describe in detail recurrence points, $ω$-limit sets and attractors.

math.DS↗

arXiv2018

Geometry of Uhlenbeck partial compactification of orthogonal instanton spaces and the K-theoretic Nekrasov partition functions

Let $M^K_n$ be the moduli space of framed $K$-instantons over $S^4$ with instanton number $n$ when $K$ is a compact simple Lie group of classical type. Let $U^{K}_{n}$ be the Uhlenbeck partial compactification of $M^{K}_{n}$. A scheme structure on $U^{K}_{n}$ is endowed by Donaldson as an algebro-geometric Hamiltonian reduction of ADHM data. In this paper, for $K=SO(N,R)$, $N\ge5$, we prove that $U^{K}_{n}$ is an irreducible normal variety with smooth locus $M^{K}_{n}$. Hence, together with the author's previous result, the K-theoretic Nekrasov partition function for any simple classical group other than $SO(3,R)$, is interpreted as a generating function of Hilbert series of the instanton moduli spaces. Using this approach we also study the case $K=SO(4,R)$ which is the unique semisimple but non-simple classical group.

math.AG↗

arXiv2016

Moduli spaces of framed symplectic and orthogonal bundles on P2 and the K-theoretic Nekrasov partition functions

Let $K$ be the compact Lie group $USp(N/2)$ or $SO(N, R)$. Let $M^K_n$ be the moduli space of framed K-instantons over $S^4$ with the instanton number $n$. By Donaldson (1984), $M^K_n$ is endowed with a natural scheme structure. It is a Zariski open subset of a GIT quotient of $μ^{-1}(0)$, where $μ$ is a holomorphic moment map such that $μ^{-1}(0)$ consists of the ADHM data. The purpose of the paper is to study the geometric properties of $μ^{-1}(0)$ and its GIT quotient, such as complete intersection, irreducibility, reducedness and normality. If $K=USp(N/2)$ then $μ$ is flat and $μ^{-1}(0)$ is an irreducible normal variety for any $n$ and even $N$. If $K = SO(N, R)$ the similar results are proven for low $n$ and $N$. As an application one can obtain a mathematical interpretation of the K-theoretic Nekrasov partition function of Nekrasov and Shadchin (2004).

math.AG↗

arXiv2016

Polycycle omega-limit sets of flows on the compact Riemann surfaces and Eulerian path

Let $(S,Φ)$ be a pair of a closed oriented surface and $Φ$ be a real analytic flow with finitely many singularities. Let $x$ be a point of $S$ with the polycycle $ω$-limit set $ω(x)$. In this paper we give topological classification of $ω(x)$. Our main theorem says that $ω(x)$ is diffeomorphic to the boundary of a cactus in the $2$-sphere $S^{2}$. Moreover $S$ is a connected sum of the above $S^{2}$ and a closed oriented surface along finitely many embedded circles which are disjoint from $ω(x)$. This gives a natural generalization to the higher genus of the main result of \cite{JL} for the genus $0$ case. Our result is further applicable to a larger class of surface flows, a compact oriented surface with corner and a $C^{1}$-flow with finitely many singularities locally diffeomorphic to an analytic flow.

math.DS↗

arXiv2009

On Homoclinic points, Recurrences and Chain recurrences of volume-preserving diffeomorphisms without genericity

Let $M$ be a manifold with a volume form $ω$ and $f : M \to M$ be a diffeomorphism of class $\mathcal{C}^1$ that preserves $ω$. In this paper, we do \textit{not} assume $f$ is $\mathcal{C}^1$-generic. We have two main themes in the paper: (1) the chain recurrence; (2) relations among recurrence points, homoclinic points, shadowability and hyperbolicity. For (1) (without assuming $M$ is compact), we have the theorem: if $f$ is Lagrange stable, then $M$ is a chain recurrent set. If $M$ is compact, then the Lagrange-stability is automatic. For (2) (assuming the compactness of $M$), we prove some various implications among notions, such as: (i) the $\mathcal{C}^1$-stable shadowability equals to the hyperbolicity of $M$; (ii) if a point $p\in M$ has a recurrence point in the unstable manifold $W^u (p, f)$ and there is no homoclinic point of $p,$ then $f$ is nonshadowable; (iii) if $f$ has the shadowing property and $p$ has a recurrence point in $W^u (p, f),$ then the recurrent point is in the limit set of homoclinic points of $p$.

math.DS↗

arXiv2005

On the existence of a crepant resolution of some moduli spaces of sheaves on an abelian surface

Let J be an abelian surface with a generic ample line bundle O(1). For n>0, the moduli space M(2, 0, 2n) of O(1)-semistable sheaves F of rank 2 with Chern classes c_1(F) = 0, c_2(F) = 2n is a singular projective variety, endowed with a holomorphic symplectic structure on the smooth locus. In this paper, we show that there does not exist a crepant resolution of M(2; 0; 2n) for n>1. This certainly implies that there is no symplectic desingularization of M(2, 0, 2n) for n>1.

math.AG↗

arXiv2005

Nonexistence of a crepant resolution of some moduli spaces of sheaves on a K3 surface

Let $M_c=M(2,0,c)$ be the moduli space of O(1)-semistable rank 2 torsion-free sheaves with Chern classes $c_1=0$ and $c_2=c$ on a K3 surface $X$ where O(1) is a generic ample line bundle on $X$. When $c=2n\geq4$ is even, $M_c$ is a singular projective variety equipped with a symplectic structure on the smooth locus. In this paper, we show that there is no crepant resolution of $M_{2n}$ for $n\geq 3$. This implies that there is no symplectic desingularization.

math.AG↗

arXiv2004

Cohomology of the moduli space of Hecke cycles

Let $X$ be a smooth projective curve of genus $g \ge 3$ and let $M_0$ be the moduli space of semistable bundles over $X$ of rank 2 with trivial determinant. Three different desingularizations of $M_0$ have been constructed by Seshadri \cite{Se1}, Narasimhan-Ramanan \cite{NR}, and Kirwan \cite{k5}. In this paper, we construct a birational morphism from Kirwan's desingularization to Narasimhan-Ramanan's, and prove that the Narasimhan-Ramanan's desingularization (called the moduli space of Hecke cycles) is the intermediate variety between Kirwan's and Seshadri's as was conjectured recently in \cite{KL}. As a by-product, we compute the cohomology of the moduli space of Hecke cycles.

math.AG↗