A note on extensions of algebraic and formal groups. II
[For part I see ibid. 206, No. 4, 567-575 (1990; Zbl 0742.14039).] We determine the groups of commutative extensions of \(W_{n,A}^ \wedge\) by \(\mathbb{G}_{m,A}^ \wedge\) or \(W_{n,A}\) by \(\mathbb{G}_{m,A}\) when \(A\) is a ring of characteristic \(p > 0\). More precisely: Let \(A\) be an \(\mathbb{F}_ p\)-algebra. Then there exist bijective homomorphisms \[ W(A)/F^ n @>\sim>> H^ 2_ 0 (W^ \wedge_{n,A}, \mathbb{G}_{m,A})\quad\text{and}\quad W^ \wedge (A)/F^ n @>\sim>> H^ 2_ 0 (W_{n,A}, \mathbb{G}_{m,A}). \] {}.
scientific article; zbMATH DE number 737173