Let $\Cal K$ be a semiprime ring and $T:\Cal K\rightarrow \Cal K$ an additive mapping such that $T(x^2)=T(x)x$ holds for all $x\in \Cal K$. Then $T$ is a left centralizer of $\Cal K$. It is also proved that Jordan centralizers and centralizers of $\Cal K$ coincide.
@article{118440, author = {Borut Zalar}, title = {On centralizers of semiprime rings}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {32}, year = {1991}, pages = {609-614}, zbl = {0746.16011}, mrnumber = {1159807}, language = {en}, url = {http://dml.mathdoc.fr/item/118440} }
Zalar, Borut. On centralizers of semiprime rings. Commentationes Mathematicae Universitatis Carolinae, Tome 32 (1991) pp. 609-614. http://gdmltest.u-ga.fr/item/118440/
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