In abstract algebra, the Cartan–Brauer–Hua theorem (named after Richard Brauer, Élie Cartan, and Hua Luogeng) is a theorem pertaining to division rings. It says that given two division rings  such that xKx−1 is contained in K for every x not equal to 0 in D, either K is contained in the center of D, or .  In other words, if the unit group of K is a normal subgroup of the unit group of D, then either  or K is central .

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Theorems in ring theory