We classify the indecomposable injective E(n)∗E(n)-comodules, where E(n) is the Johnson-Wilson homology theory. They are suspensions of the Jn,r = E(n)∗(MrE(r)) where 0 ≤ r ≤ n, with the endomorphism ring of Jn,r being Ê(r) ∗ Ê(r), where Ê(r) denotes the completion of E(r).

Abstract Let S be a domain and R = [ t ; σ, δ ] skew polynomial ring, where σ is an injective endomorphism of left -derivation. We give criteria for polynomials f ∈ degree less or equal to four irreducible. apply them low in quantized Weyl algebras the quantum planes. also consider ( ) m − .

Abstract In supersingular isogeny-based cryptography, the path-finding problem reduces to endomorphism ring problem. Can be reduced knowing just one endomorphism? It is known that a small degree enables polynomial-time and computation (in: Love Boneh, ANTS XIV-Proceedings of Fourteenth Algorithmic Number Theory Symposium, volume 4 Open Book Ser. Math. Sci. Publ., Berkeley, 2020). An gives an ex...

Let I denote an ideal of a local Gorenstein ring (R, m). Then we show that the local cohomology module H I (R), c = height I, is indecomposable if and only if V (Id) is connected in codimension one. Here Id denotes the intersection of the highest dimensional primary components of I. This is a partial extension of a result shown by Hochster and Huneke in the case I the maximal ideal. Moreover th...

Let R be a local ring of positive characteristic and X complex with nonzero finitely generated homology finite injective dimension. We prove that if the derived base change via Frobenius (or more generally, contracting) endomorphism has dimension then is Gorenstein. In particular, we give an affirmative answer to question by Falahola Marley [7, Question 3.9].

In 1969 Kunz [Ku] proved a fundamental result, connecting the regularity of a local ring of positive characteristic with the flatness of its Frobenius endomorphism φ. This was a first indication of the important role that φ would play in homological commutative algebra, especially in reflecting basic homological properties of the ring. Some results in Peskine and Szpiro’s groundbreaking thesis,...