On association schemes all elements of which have valency 1 or 2

On Ideals Which Have the Weakly Insertion of Factors Property

A one-sided ideal of a ring has the insertion of factors property (or simply, IFP) if implies r for . We say a one-sided ideal of has the weakly IFP if for each , implies , for some non-negative integer . We give some examples of ideals which have the weakly IFP but have not the IFP. Connections between ideals of which have the IFP and related ideals of some ring extensions a...

Association schemes generated by a non-symmetric relation of valency 2

We give some observations on association schemes with a relation of valency 2 from the representation theory of Bose–Mesner algebras and the basic structure theory. One of the applications of these observations is the classi-cation of the association schemes with a non-symmetric relation of valency 2 if the cardinality of the point set is a product of two primes, and another is the proof of Li’...

Association Schemes All of Whose Symmetric Fusion Schemes Are Integral

In this paper we aim to characterize association schemes all of whose symmetric fusion schemes have only integral eigenvalues, and classify those obtained from a regular action of a finite group by taking its orbitals.

Hypergraphs in which all disjoint pairs have distinct unions

Integration, independence or employment? Or can you have it all?