Characteristic cover

Description

A Cover is called characteristic if its (smaller) Fundamental group is a Characteristic subgroup in of the base fundamental group.

Definition

Let $p:{\Sigma }^{\prime }\to \Sigma$ be a Cover. $p$ is called characteristic if the subgroup ${\pi }_1({\Sigma }^{\prime })\subseteq {\pi }_1(\Sigma )$ is a Characteristic subgroup.

Properties

Tip

Examples

Example