arXiv subjects
Publications and source records attributed to Eugene Z. Xia.
We prove that the mapping class group of a closed surface acts ergodically on connected components of the representation variety corresponding to a connected compact Lie group.
For a compact Riemann surface $X$ of genus $g > 1$, $\Hom(π_1(X), U(p,1))/U(p,1)$ is the moduli space of flat $\U(p,1)$-connections on $X$. There is an integer invariant, $τ$, the Toledo invariant associated with each element in $\Hom(π_1(X), U(p,1))/U(p,1)$. If $q = 1$, then $-2(g-1) \le τ\le 2(g-1)$. This paper shows that $\Hom(π_1(X), U(p,1))/U(p,1)$ has one connected component corresponding to each $τ\in 2Z$ with $-2(g-1) \le τ\le 2(g-1)$. Therefore the total number of connected components is $2(g-1) + 1$.
Let M be a one-holed torus with boundary $\partial M$ (a circle) and $Γ$ the mapping class group of M fixing $\partial M$. The group $Γ$ acts on ${\mathcal M}_{\mathcal C}(SU(2))$ which is the space of SU(2)-gauge equivalence classes of flat SU(2)-connections on M with fixed holonomy on $\partial M$. We study the topological dynamics of the $Γ$-action and give conditions for the individual $Γ$-orbits to be dense in ${\mathcal M}_{\mathcal C}(SU(2))$.
Let M be a Riemann surface with boundary $\partial M$ and genus greater than zero. Let $Γ$ be the mapping class group of M fixing $\partial M$. The group $Γ$ acts on ${\mathcal M}_{\mathcal C} = \Hom_{\mathcal C}(π_1(M),SU(2)/SU(2)$ which is the space of SU(2)-gauge equivalence classes of flat SU(2)-connections on M with fixed holonomy on $\partial M$. We study the topological dynamics of the $Γ$-action and give conditions for the individual $Γ$-orbits to be dense in ${\mathcal M}_{\mathcal C}$.
Let X be a projective curve of genus 2 over an algebraically closed field of characteristic 2. The Frobenius map on X induces a rational map on the moduli scheme of rank-2 bundles. We show that up to isomorphism, there is only one (up to tensoring by an order two line bundle) semi-stable vector bundle of rank 2 (with determinant equal to a theta characteristic) whose Frobenius pull-back is not semi-stable. The indeterminacy of the Frobenius map at this point can be resolved by introducing Higgs bundles.
Let $X$ be a projective curve of genus 2 over an algebraically closed field of characteristic 2. The Frobenius map on X induces a rational map on the moduli space of rank-2 bundles. We show that up to isomorphism, there is only one (up to tensoring by an order two line bundle) semi-stable vector bundle of rank 2 with determinant equal to a theta characteristic whose Frobenius pull-back is not stable. The indeterminacy of the Frobenius map at this point can be resolved by introducing Higgs bundles.