主讲人：Prof. Dechao Zheng（Chongqing University And Vanderbilt University）

时  间：5月22日（周三）16：00-17：00

地  点：威尼斯欢乐娱人城1099北二区教学楼 516 教室

备  注：ABSTRACT. On the Hardy space, by means of an elegant and ingenious argument, Widom showed that the spectrum of a bounded Toeplitz operator is always connected and Douglas showed that the essential spectrum of a bounded Toeplitz operator is also connected. On the Bergman space, in 1979, G. McDonald and the C. Sundberg showed that the essential spectrum of T' is connected for ' a harmonic function on the unit disk which is either real or piecewise continuous on the boundary. They asked whether the essential spectrum of a Toeplitz operator on the Bergman space with bounded harmonic symbol is connected. In this talk, we will show an example that the spectrum and the essential spectrum of a Toeplitz operator with bounded harmonic symbol is disconnected. This is a joint work with Carl Sundberg. Date: June 24, 2011. 1