Metric characterisation of unitaries in JB${}^{\ast }$-algebras

María Cueto-Avellaneda, Antonio M. Peralta

Let $M$ be a unital JB${}^{\ast }$-algebra whose closed unit ball is denoted by ${\mathcal{B}}_M$. Let ${\partial }_e({\mathcal{B}}_M)$ denote the set of all extreme points of ${\mathcal{B}}_M$. We…