In [6] J.F. Feinstein constructed a compact plane set X such that R(X) has no non-zero, bounded point derivations but is not weakly amenable. In the same paper he gave an example of a separable uniform algebra A such that every point in the character space of A is a peak point but A is not weakly amenable. We show that it is possible to modify the construction in order to produce examples which...

A dominating set D of a graph G is a subset of V (G) such that for every vertex v ∈ V (G), either v ∈ D or there exists a vertex u ∈ D that is adjacent to v in G. Dominating sets of small cardinality are of interest. A connected dominating set C of a graph G is a dominating set of G such that the subgraph induced by the vertices of C in G is connected. A weakly-connected dominating set W of a g...

The weakly compact reflection principle Reflwcpκq states that κ is a weakly compact cardinal and every weakly compact subset of κ has a weakly compact proper initial segment. The weakly compact reflection principle at κ implies that κ is an ω-weakly compact cardinal. In this article we show that the weakly compact reflection principle does not imply that κ is pω ` 1qweakly compact. Moreover, we...

We utilize recent results of André and Gabber on the existence weakly functorial, integral perfectoid big Cohen–Macaulay (BCM) algebras to study singularities local rings in mixed characteristic. In particular, we introduce a characteristic BCM-variant rational/F-rational singularities, log terminal/F-regular multiplier/test ideals divisor pairs. prove number about these objects including restr...

We define the notion of weakly ordered semigroups. For this class of semigroups, we compute the radical of the semigroup algebras. This generalizes some results on left regular bands and on 0Hecke algebras.

As a generalization of Deza graphs, we introduce Deza digraphs and describe the basic theory of these graphs. We also prove the necessary and sufficient conditions when a weakly distance-regular digraph is a Deza digraph.

We prove that, for an analytic family of “weakly tame” regular functions on an affine manifold, the spectrum at infinity of each function of the family is semicontinuous in the sense of Varchenko.