학술논문
On rings as unions of four subrings
Document Type
Working Paper
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Source
Subject
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Abstract
The covering number of an associative ring $R$ is the minimal number of proper subrings whose union is $R$. We establish a strategy to classify unital rings of a given finite covering number, and obtain a classification of unital rings whose covering number is four. Along the way we compute the covering number of every finite local ring whose residue field has prime order.
Comment: Article reorganized; full classification now proved
Comment: Article reorganized; full classification now proved