The of rings with many units
The main result of the paper characterizes continuous local derivations on a class of commutative Banach algebra that all of its squares are positive and satisfying the following property: Every continuous bilinear map from into an arbitrary Banach space such that whenever , satisfies the condition for all .
For each squarefree monomial ideal , we associate a simple finite graph by using the first linear syzygies of . The nodes of are the generators of , and two vertices and are adjacent if there exist variables such that . In the cases, where is a cycle or a tree, we show that has a linear resolution if and only if has linear quotients and if and only if is variable-decomposable. In addition, with the same assumption on , we characterize all squarefree monomial ideals with a...
Let be an algebraically closed field of characteristic . We study obstructions to lifting to characteristic the faithful continuous action of a finite group on . To each such a theorem of Katz and Gabber associates an action of on a smooth projective curve over . We say that the KGB obstruction of vanishes if acts on a smooth projective curve in characteristic in such a way that and have the same genus for all subgroups . We determine for which the KGB obstruction...
In 1950 in volume 1 of Proc. Amer. Math. Soc., B. Brown and N. McCoy showed that every (not necessarily commutative) ring has an ideal consisting of elements for which there is an such that , and maximal with respect to this property. Considering only the case when is commutative and has an identity element, it is often not easy to determine when is not just the zero ideal. We determine when this happens in a number of cases: Namely when at least one of or has a von Neumann inverse,...