orthogonal group
Let be a non-degenerate symmetric bilinear form over the real vector space . A linear transformation is said to preserve if for all vectors . The subgroup
of the general linear group
consisting of all linear transformations that preserve is called the orthogonal group
with respect to , and denoted .
If is also positive definite (i.e., is an inner product), then is equivalent to the group of invertible linear transformations that preserve the standard inner product on , and in this case the group is usually denoted .
Elements of are called orthogonal transformations.One can show that a linear transformation is an orthogonal transformation if and only if (i.e., the inverse of equals the transpose
of ).