On separable extensions of group rings and quaternion rings

On Separable Abelian Extensions of Rings

Let R be a ring with I, G (= (1>x...Xm) a finite abelian automorphism group of R of order n where (i2 is cyclic of order n. for some integers n, hi, and m, and C the center of R whose automorphism group induced by G is isomorphic with G. Then an abelian extension Rtx 1,...,xm is defined as a generalization of cyclic extensions of rings, and RXl,...,Xm is an Azumaya algebra over K (= CG {c in C ...

Group Extensions and Automorphism Group Rings

We use extensions to study the semi-simple quotient of the group ring FpAut(P ) of a finite p-group P . For an extension E : N → P → Q, our results involve relations between Aut(N), Aut(P ), Aut(Q) and the extension class [E] ∈ H(Q,ZN). One novel feature is the use of the intersection orbit group Ω([E]), defined as the intersection of the orbits Aut(N) · [E] and Aut(Q) · [E] in H(Q,ZN). This gr...

Extensions of Nilpotent P.P. Rings

Extensions of strongly alpha-reversible rings

We introduce the notion ofstrongly $alpha$-reversible rings which is a strong version of$alpha$-reversible rings, and investigate its properties. We firstgive an example to show that strongly reversible rings need not bestrongly $alpha$-reversible. We next argue about the strong$alpha$-reversibility of some kinds of extensions. A number ofproperties of this version are established. It is shown ...

Hyperbolicity of orders of quaternion algebras and group rings

For a given division algebra of the quaternions, we construct two types of units of its Z-orders: Pell units and Gauss units. Also, if K = Q √ −d, d ∈ Z \ {0, 1} is square free and R = IK , we classify R and G such that U1(RG) is hyperbolic. In particular, we prove that U1(RK8) is hyperbolic iff d > 0 and d ≡ 7 (mod 8). In this case, the hyperbolic boundary ∂(U1(RG)) ∼= S, the two dimensional s...