for a ring endomorphism $alpha$ and an $alpha$-derivation $delta$, we introduce a concept, so called skew $pi$-armendariz ring, that is a generalization of both $pi$-armendariz rings, and $(alpha,delta)$-compatible skew armendariz rings. we first observe the basic properties of skew $pi$-armendariz rings, and extend the class of skew $pi$-armendariz rings through various ring extensions. we nex...

Lifting modules and their various generalizations as some main concepts in module theory have been studied and investigated extensively in recent decades. Some authors tried to present some homological aspects of lifting modules and -supplemented modules. In this work, we shall present a homological approach to -supplemented modules via fully invariant submodules. Lifting modules and H-suppleme...

We introduce an invariant of the hyperbolic 3-manifolds which appears in the K-theory of certain C*-algebras. Namely, such an invariant is essentially the integral order in an algebraic number field K with a fixed equivalence class of ideals in the ring of integers of K. The C*-algebras in question are the crossed product C*-algebras attached to the monodromy transformation of the 3-manifolds w...

We examine the Johnson filtration of the (outer) automorphism group of a finitely generated group. In the case of a free group, we find a surprising result: the first Betti number of the second subgroup in the Johnson filtration is finite. Moreover, the corresponding Alexander invariant is a module with non-trivial action over the Laurent polynomial ring. In the process, we show that the first ...

Let Γ denote a group of finite virtual cohomological dimension and p a prime. If the cohomology ring H∗(Γ;Fp) has Krull dimension one, the p-period of Γ is defined; it measures the periodicity of H∗(Γ;Fp) in degrees above the virtual cohomological dimension of Γ. The Yagita invariant p(Γ) of Γ is a natural generalization of the p-period to groups with H∗(Γ;Fp) of Krull dimension larger than one...

For a polynomial ring S in n variables, we consider the natural action of symmetric group Sn on by permuting variables. an Sn-invariant monomial ideal I?S and j?0, give explicit recipe for computing modules ExtSj(S/I,S), use this to describe projective dimension regularity I. We classify ideals I that have linear free resolution, also characterize those which are Cohen–Macaulay. then two settin...

A bstract We find the set of generalized symmetries associated with free graviton theory in four dimensions. These are generated by gauge invariant topological operators that violate Haag duality ring-like regions. As expected from general QFT grounds, we a “electric” and dual “magnetic” compute their algebra. To do so, describe using phase space gauge-invariant electric magnetic variables cons...

Let R be a local ring and C semidualizing module of R. We investigate the behavior certain classes generalized Cohen-Macaulay R-modules under Foxby equivalence between Auslander Bass with respect to C. In particular, we show that are invariant this if M is finitely generated R-module in class such C\otimes_RM surjective Buchsbaum, then also Buchsbaum.

in this paper, we introduce the new notion of n-f-clean rings as a generalization of f-clean rings. next, we investigate some properties of such rings. we prove that mn(r) is n-f-clean for any n-f-clean ring r. we also, get a condition under which the denitions of n-cleanness and n-f-cleanness are equivalent.