A proper group action is a group action of a topological group 
on a topological space 
for which the mapping
 |
is a proper map, i.e., inverses of compact sets are compact.
A proper action must have compact isotropy groups at all points of 
.
Proper Group Action
See also
Group ActionExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Proper Group Action." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ProperGroupAction.html