High Quality Content by WIKIPEDIA articles! In mathematics, the Schur orthogonality relations express a central fact about representations of finite groups. They admit a generalization to the case of compact groups in general, and in particular compact Lie groups, such as the rotation group SO(3). The other two Kronecker delta's state that the row and column indices must be equal (n = n' and m = m') in order to obtain a non-vanishing result. This theorem is also known as the Great Orthogonality Theorem. Every group has an identity representation (all group elements mapped onto the real number 1).