If the parameters of a Lie group vary over a closed interval, them the Lie group is said to be compact. Every representation of a compact group is equivalent to a unitary representation.
Compact Lie Group
See also
Lie GroupExplore with Wolfram|Alpha
References
Huang, J.-S. "Compact Lie Groups." Part 3 in Lectures on Representation Theory. Singapore: World Scientific, pp. 71-128, 1999.Referenced on Wolfram|Alpha
Compact Lie GroupCite this as:
Weisstein, Eric W. "Compact Lie Group." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/CompactLieGroup.html