Published online by Cambridge University Press: 18 July 2013
Here we prove that, for a $2$-primal ring
$R$, the Laurent series ring
$R((x))$ is a clean ring if and only if
$R$ is a semiregular ring with
$J(R)$ nil. This disproves the claim in K. I. Sonin [‘Semiprime and semiperfect rings of Laurent series’, Math. Notes 60 (1996), 222–226] that the Laurent series ring over a clean ring is again clean. As an application of the result, it is shown that, for a
$2$-primal ring
$R$,
$R((x))$ is semiperfect if and only if
$R((x))$ is semiregular if and only if
$R$ is semiperfect with
$J(R)$ nil.