arXiv subjects

Alexander York

Publications and source records attributed to Alexander York.

3 recordsLinked to original sources

arXiv2018

Linkage and Intermediate C-Gorenstein Dimensions

This paper brings together two theories in algebra that have had been extensively developed in recent years. First is the study of various homological dimensions and what information such invariants can give about a ring and its modules. A collection of intermediate C-Gorenstein dimensions is defined and this allows generalizations of results concerning C-Gorenstein dimension and certain Serre-like conditions. Second is the theory of linkage first introduced by Peskine and Szpiro and generalized to modules by Martinskovsky and Strooker. Using the further generalization of module linkage of Nagel, results are proven connecting linkage with these homological dimensions and Serre-like conditions.

math.AC↗

arXiv2018

An Extension of a Theorem of Frobenius and Stickelberger to Modules of Projective Dimension One over a Factorial Domain

Let $R$ be a commutative ring. A quasi-Gorenstein $R$-module is an $R$-module such that the grade of the module and the projective dimension of the module are equal and the canonical module of the module is isomorphic to the module itself. After discussing properties of finitely generated quasi-Gorenstein modules, it is shown that this definition allows for a characterization of diagonal matrices of maximal rank over a Noetherian factorial domain $R$ extending a theorem of Frobenius and Stickelberger to modules of projective dimension 1 over a commutative Noetherian factorial domain.

math.AC↗

arXiv2015

A Note on Weighted Rooted Trees

Let $T$ be a tree rooted at $r$. Two vertices of $T$ are related if one is a descendant of the other; otherwise, they are unrelated. Two subsets $A$ and $B$ of $V(T)$ are unrelated if, for any $a\in A$ and $b\in B$, $a$ and $b$ are unrelated. Let $\omega$ be a nonnegative weight function defined on $V(T)$ with $\sum_{v\in V(T)}\omega(v)=1$. In this note, we prove that either there is an $(r, u)$-path $P$ with $\sum_{v\in V(P)}\omega(v)\ge \frac13$ for some $u\in V(T)$, or there exist unrelated sets $A, B\subseteq V(T)$ such that $\sum_{a\in A }\omega(a)\ge \frac13$ and $\sum_{b\in B }\omega(b)\ge \frac13$. The bound $\frac13$ is tight. This answers a question posed in a very recent paper of Bonamy, Bousquet and Thomass\'e.

math.CO↗