One shows that for two C-algebras A1 and A2 any continuous function on Prim(A1)×Prim(A2) can be continuously extended to Prim(A1⊗min A2) provided it takes its values in a T1 topological space. This generalizes [5, Corollary 3.4]. A new proof is given for a result of Archbold [2] about the space of minimal primal ideals of A1 ⊗min A2. To obtain these two results one makes use of the topological ...

Since the theory of ideals plays an important role in the theory of semirings, in this paper we will make an intensive study of the notions of primal and weakly primal ideals in commutative semirings with an identity 1. It is shown that these notions inherit most of the essential properties of the primal and weakly primal ideals of a commutative ring with non-zero identity. Also, the relationsh...

Let (T,M) be a complete local domain containing the integers. Let p1 ⊆ p2 ⊆ · · · ⊆ pn be a chain of nonmaximal prime ideals of T such that Tpn is a regular local ring. We construct a chain of excellent local domains An ⊆ An−1 ⊆ · · · ⊆ A1 such that for each 1 ≤ i ≤ n, the completion of Ai is T , the generic formal fiber of Ai is local with maximal ideal pi, and if I is a nonzero ideal of Ai th...

For a radical monomial ideal I in a normal semigroup ring k[Q], there is a unique minimal irreducible resolution 0 → k[Q]/I → W 0 → W 1 → · · · by modules W i of the form ⊕ j k[Fij ], where the Fij are (not necessarily distinct) faces of Q. That is, W i is a direct sum of quotients of k[Q] by prime ideals. This paper characterizes Cohen–Macaulay quotients k[Q]/I as those whose minimal irreducib...

Let R be a commutative ring with nonzero identity. A proper ideal I of is said to 1-absorbing prime if xyz ∈ for some nonunits x, y, z R, then xy or I. It well known that ⇒ primary semi-primary ideal, is, the class ideals comes between classes and ideals. Also, above right arrows are not reversible. In this article, we characterize rings over which every prime. by comparing other classical such...

Given an elliptic fibration $f \colon X \to S$ over the spectrum of a complete discrete valuation ring with algebraically closed residue field, we use Hochschild--Serre spectral sequence to express torsion in $R^1f_\ast \mathscr{O}_X$ as first group cohomology $H^1(G,H^0(S^\prime, \mathscr{O}_{S^\prime}))$. Here, $G$ is Galois maximal extension $K^\prime / K$ such that normalization $X \times_S...

0→ Ps → · · · → Pi → 0 where each Pi is a finitely generated projective R-module. Let P the full subcategory of D consisting of complexes isomorphic to perfect complexes. These are precisely the compact objects, also called small objects, in D. These notes are an abstract of two lectures I gave at the workshop. The main goal of the lectures was to present various proofs of a theorem of Hopkins ...

We study topological properties of the correspondence of prime spectra associated to a noncommutative ring homomorphism R → S. Our main result provides criteria for the adjointness of certain functors between the categories of Zariski closed subsets of SpecR and SpecS; these functors arise naturally from restriction and extension of scalars. When R and S are left noetherian, adjointness occurs ...

Let K be a number field and OK be the ring of algebraic integers. We discuss the unique factorization of elements of OK into irreducibles and its use in solving Diophantine equations. We then proceed to prove the existence of the unique factorization of ideals of OK into prime ideals.