|Oct 24, 2016
|Aoyama Gakuin University
Burger, Iozzi and Wienhard defined bounded Euler number for actions of the fundamental group of connected oriented surfaces of finite type possibly with punctures on the circle by orientation preserving homeomorphisms. Bounded Euler number can be extended to actions of 2-orbifold groups. We discuss Milnor-wood type inequality and rigidity phenomenon involving bounded Euler number for actions of certain 2-orbifold groups, such as the modular group.