Following the well-established terminology in commutative algebra, any (not necessarily commutative) finite-dimensional local algebra A $A$ with radical J $J$ will be said to short provided 3 = 0 $J^3 0$ . As case, we show: If a has an indecomposable non-projective Gorenstein-projective module M $M$ , then either is self-injective (so that all modules are Gorenstein-projective) and then, of cou...

In this paper we introduce techniques to gauge the torsion of the tensor product A ⊗R B of two finitely generated modules over a Noetherian ring R. The outlook is very different from the study of the rigidity of Tor carried out in the work of Auslander ([1]) and other authors. Here the emphasis in on the search for bounds for the torsion part of A⊗R B in terms of global invariants of A and of B...

Unstable modules over the Steenrod algebra with only top $k$ operations are introduced in language of ringoids. We prove category such has homological dimension at most $k$. A pratical method, which generalizes $\Lambda$ complex, to compute $\mathrm{Ext}$ group from spheres is proposed. also able establish several functors relate and unstable algebra, describe connections between groups them.

The concept of the homotopy theory of modules was discovered by Peter Hilton as a result of his trip in 1955 to Warsaw, Poland, to work with Karol Borsuk, and to Zurich, Switzerland, to work with Beno Eckmann. The idea was to produce an analog of homotopy theory in topology. Yet, unlike homotopy theory in topology, there are two homotopy theories of modules, the injective theory, πn(A,B), and t...

Let k be a field and let Q be a (finite) quiver. We fix a representation S with EndkQ S = k and Ext 1 kQ(S, S) = 0. In analogy to [3, Section 1] we consider the following subcategories of repk Q. Let M S be the full subcategory of all modules X with ExtkQ(S,X) = 0 such that, in addition, X has no direct summand which can be embedded into some direct sum of copies of S. Similarly, let MS be the ...

We investigate the behavior of Castelnuovo-Mumford regularity with respect to some classical functors : Tor, the Frobenius functor in positive characteristic, taking a power or a product (on ideals). These generalizes and refines previous results on these issues by several authors. As an application we provide results on the regularity of an intersection of subschemes of a projective scheme, un...

It is proved that for a ring R either an affine algebra over field, or equicharacteristic complete local ring, some power of the Jacobian ideal annihilates ExtRd+1(−,−), where d Krull dimension R. Sufficient conditions are identified under which itself these Ext-modules, and examples provided show this not always case. The crucial new idea to consider derived version Noether different algebra.