Uniqueness of the involution on a $C^*$-algebra Stack Exchange Network Stack Exchange network consists of 183 Q A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers
Wild automorphisms of the complex numbers Given any field automorphism of $\mathbb C$, the rational numbers are fixed In fact, any number that is explicitly definable in $\mathbb C$ (in the first order language of fields) is fixed