Just when looking at the definition of a $*$-algebra, or a Banach $*$ -algebra, we need the involution to verify $(ab)^*=b^*a^*$, so I am wondering what are some examples of involutions ( $(a^*)^*= a$ ) which are not satisfying $(ab)^*=b^*a^*$ in general?
2026-04-18 14:19:25.1776521965
An involution but without $(ab)^*=b^*a^*$?
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