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Let S be a commutative complete discrete valuation domain of positive characteristic p, S* the unit group of S, Ω a subgroup of S* and $G=G_p\times B$ a finite group, where $G_p$ is a p-group and B is a p’-group. Denote by $S^{\lambda }G$ the twisted group algebra of G over S with a 2-cocycle λ ∈ Z²(G,S*). For Ω satisfying a specific condition, we give necessary and sufficient conditions for G to be of OTP projective (S,Ω)-representation type, in the sense that there exists a cocycle λ ∈ Z²(G,Ω) such that every indecomposable...

Let S be a commutative local ring of characteristic p, which is not a field, S* the multiplicative group of S, W a subgroup of S*, G a finite p-group, and $S^{\lambda }G$ a twisted group ring of the group G and of the ring S with a 2-cocycle λ ∈ Z²(G,S*). Denote by $In{d}_m\left(S^{\lambda }G\right)$ the set of isomorphism classes of indecomposable $S^{\lambda }G$-modules of S-rank m. We exhibit rings $S^{\lambda }G$ for which there exists a function $f_{\lambda }:\mathbb{N}\to \mathbb{N}$ such that $f_{\lambda }\left(n\right)\ge n$ and $In{d}_{f_{\lambda }\left(n\right)}\left(S^{\lambda }G\right)$ is an infinite set for every natural n > 1. In special cases $f_{\lambda }\left(\mathbb{N}\right)$ contains every natural number m >...

Assume that S is a commutative complete discrete valuation domain of characteristic p, S* is the unit group of S and $G=G_p\times B$ is a finite group, where $G_p$ is a p-group and B is a p’-group. Denote by $S^{\lambda }G$ the twisted group algebra of G over S with a 2-cocycle λ ∈ Z²(G,S*). We give necessary and sufficient conditions for $S^{\lambda }G$ to be of OTP representation type, in the sense that every indecomposable $S^{\lambda }G$-module is isomorphic to the outer tensor product V W of an indecomposable $S^{\lambda }{G}_p$-module V and an irreducible $S^{\lambda }B$-module...

Let $\mathbb{Z}{̂}_p$ be the ring of p-adic integers, $U\left(\mathbb{Z}{̂}_p\right)$ the unit group of $\mathbb{Z}{̂}_p$ and $G=G_p\times B$ a finite group, where $G_p$ is a p-group and B is a p’-group. Denote by $\mathbb{Z}{̂}_p^{\lambda }G$ the twisted group algebra of G over $\mathbb{Z}{̂}_p$ with a 2-cocycle $\lambda \in Z²(G,U\left(\mathbb{Z}{̂}_p\right))$. We give necessary and sufficient conditions for $\mathbb{Z}{̂}_p^{\lambda }G$ to be of OTP representation type, in the sense that every indecomposable $\mathbb{Z}{̂}_p^{\lambda }G$-module is isomorphic to the outer tensor product V W of an indecomposable $\mathbb{Z}{̂}_p^{\lambda }{G}_p$-module V and an irreducible $\mathbb{Z}{̂}_p^{\lambda }B$-module W.