We study the local Gromov-Witten invariants of O（k）⊕O（-k-2） → P1 by localization techniques and the Marino-Vafa formula, using suitable circle actions. They are identified with the equivariant Riemann-Roch indices of some power of the determinant of the tautological sheaves on the Hilbert schemes of points on the affine plane. We also compute the corresponding Gopakumar-Vafa invariants and make some conjectures about them.
设 x:M→R^(n+1)是凸域ΩR^n 上的严格凸函数 x_(n+1)=f(x_1,…,x_n)定义的一个局部强凸超曲面.如果 f 是下面方程的解,则称 M 为α相对极值超曲面:△ρ=(2-nα)/2(‖▽ρ‖~2)/ρ,ρ:=(det((a^2f)/(ax_iax_j)))^(1/(n+2)).2007年,贾和李证明了存在一个仅依赖于维数 n 的正常数 K(n),如果|α|≥K(n),那么欧氏完备的α相对极值超曲面是椭圆抛物面.本文中我们利用 Calabi 度量给出了这个定理的一个简单证明.
I.A.B. Strachan introduced the notion of a natural Frobenius submanifold of a Frobenius manifold and gave a sufficient but not necessary condition for a submanifold to be a natural Frobenius submanifold. This article will give a necessary and sufficient condition and classify the natural Frobenius hypersurfaces.
Let G be arbitrary finite group,define H G· (t;p +,p) to be the generating function of G-wreath double Hurwitz numbers.We prove that H G· (t;p +,p) satisfies a differential equation called the colored cutand-join equation.Furthermore,H G·(t;p +,p) is a product of several copies of tau functions of the 2-Toda hierarchy,in independent variables.These generalize the corresponding results for ordinary Hurwitz numbers.
We define and compute by localizating the local equivariant Gromov-Witten invariants of the canonical line bundles of toric surfaces,not necessarily Fano.
YANG Fei & ZHOU Jian Department of Mathematical Sciences,Tsinghua University,Beijing 100084,China
We study the ordinary differential equations related to rotationally symmetric pseudo-Khler metricsof constant scalar curvatures. We present various solutions on various holomorphic line bundles over projectivespaces and their disc bundles, and discuss the phase change phenomenon when one suitably changes initialvalues.
