Let X be a finite set and let k be a commutative ring. We consider the k-algebra of the monoid of all relations on X, modulo the ideal generated by the relations factorizing through a set of cardinality strictly smaller than Card(X), called inessential relations. This quotient is called the essential algebra associated to X. We then define a suitable nilpotent ideal of the essential algebra and...

In this article we consider the intersection graph G(R) of nontrivial proper ideals of a finite commutative principal ideal ring R with unity 1. Two distinct ideals are adjacent if they have non-trivial intersection. We characterize when the intersection graph is complete, bipartite, planar, Eulerian or Hamiltonian. We also find a formula to calculate the number of ideals in each ring and the d...

For a fixed pattern graph H , let H -CONTRACTIBILITY denote the problem of deciding whether a given input graph is contractible to H . This article is part II of our study on the computational complexity of the H -CONTRACTIBILITY problem. In the first article we pinpointed the complexity for all pattern graphswith five vertices except for two pattern graphs H . Here, we present polynomial time ...

It is shown that a commutative Bézout ring R with compact minimal prime spectrum is an elementary divisor ring if and only if so is R/L for each minimal prime ideal L. This result is obtained by using the quotient space pSpec R of the prime spectrum of the ring R modulo the equivalence generated by the inclusion. When every prime ideal contains only one minimal prime, for instance if R is arith...

This paper formalizes the idea that firms can (partly) overcome the static costs associated with low contractibility by engaging in long-term relationships, but that the rigidity of these relationships may lead to strong dynamic ineffi ciencies. Specifically, we consider the repeated interaction between a final good producer and an intermediate input supplier. A pair producer/supplier can be a ...

We recall that Theorem 1.3 allows us to define the ideal class group of a Dedekind domain, and in particular of a ring of integers, as the group of fractional ideals modulo the subgroup of principal ideals. We will prove that in the case of a ring of integers, the ideal class group is finite. In fact, we will shortly give a stronger statement due to Minkowski. Using similar techniques, we will ...

In the ideal topological spaces (X, ?, I) and (Y, J, ?), we define (I, J)-irresolute function, weakly-(I, J)-irresolute, strongly-(I, functions, semi-I-open sets quasi-H-closed modulo I. We discuss properties of function mapping connected, closed, compact I semi-I-isolated points. J)-Homeomorphisim on presemi-I-open closure subsets are explored in this paper.

We study tight closure and test ideals in rings of characteristic p 0 using resolution of singularities. The notions of F -rational and F regular rings are defined via tight closure, and they are known to correspond with rational and log terminal singularities, respectively. In this paper, we reformulate this correspondence by means of the notion of the test ideal, and generalize it to wider cl...