C-star identity
= C-star identity
{c}
{title2=$\lVert a^*a\rVert=\lVert a\rVert^2$}
The C-star identity is the norm axiom $\lVert a^*a\rVert=\lVert a\rVert^2$. It implies that the involution is isometric and that a normal element has norm equal to its spectral radius.