Linear maps preserving products equal to primitive idempotents of an incidence algebra

Abstract

Let $A$, $B$ be algebras and $a\in A$, $b\in B$ a fixed pair of elements. We say that a map $\phi :A\to B$ preserves products equal to $a$ and $b$ if for all $a_1,a_2\in A$ the equality $a_1{a}_2=a$ implies $\phi (a_1)\phi (a_2)=b$. In this paper we study bijective linear maps $\phi :I(X,F)\to I(X,F)$ preserving products equal to primitive idempotents of $I(X,F)$, where $I(X,F)$ is the incidence algebra of a finite connected poset $X$ over a field $F$. We fully characterize the situation, when such a map $\phi$ exists, and whenever it does, $\phi$ is either an automorphism of $I(X,F)$ or the negative of an automorphism of $I(X,F)$.

arXiv commentAccepted for publication in Journal of Algebra. We thank the referee for pointing out inaccuracies throughout the text and suggestions that improved its clarity