Trace identity

In mathematics, a trace identity is any equation involving the trace of a matrix.
Example.
For example, the Cayley–Hamilton theorem says that every matrix satisfies its own characteristic polynomial.
Properties.
Trace identities are invariant under simultaneous conjugation.
Uses.
They are frequently used in the invariant theory of "n"×"n" matrices to find the generators and relations of the ring of invariants, and therefore are useful in answering questions similar to that posed by Hilbert's fourteenth problem.