Let 
be a representation for a group of group
order 
,
then
 |
The proof is nontrivial and may be found in Eyring et al. (1944).
Group Orthogonality Theorem
See also
Group, Group Character, Irreducible RepresentationExplore with Wolfram|Alpha
References
Eyring, H.; Walter, J.; and Kimball, G. E. Quantum Chemistry. New York: Wiley, p. 371, 1944.Referenced on Wolfram|Alpha
Group Orthogonality TheoremCite this as:
Weisstein, Eric W. "Group Orthogonality Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/GroupOrthogonalityTheorem.html