Korean J. Math.  Vol 29, No 3 (2021)  pp.483-492
DOI: https://doi.org/10.11568/kjm.2021.29.3.483

Reduced property over idempotents

Tai Keun Kwak, Yang Lee, Young Joo Seo


This article concerns the property that for any element $a$ in a ring, if $a^{2n}=a^n$ for some $n\geq 2$ then $a^2=a$.  The class of rings with this property is large, but there also exist  many kinds of rings without that, for example, rings  of characteristic $\neq 2$ and finite fields of characteristic  $\geq 3$.  Rings with such a property is called {\it reduced-over-idempotent}. The study of reduced-over-idempotent rings is based on the fact that the characteristic is $2$ and every nonzero non-identity element generates an infinite multiplicative semigroup without identity.   It is proved that the reduced-over-idempotent property pass to polynomial rings, and we provide power series rings with a partial affirmative argument. It is also proved that every finitely generated subring of a locally finite reduced-over-idempotent ring is isomorphic to a finite direct product of copies of the prime field $\{0,1\}$.  A method to construct reduced-over-idempotent fields is also provided.


reduced-over-idempotent ring; idempotent; reduced ring; Abelian ring; characteristic; unit; polynomial ring; power series ring

Subject classification



National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT)

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