ﻻ يوجد ملخص باللغة العربية
Let $cX$ be a family of subsets of a finite set $E$. A matroid on $E$ is called an $cX$-matroid if each set in $cX$ is a circuit. We consider the problem of determining when there exists a unique maximal $cX$-matroid in the weak order poset of all $cX$-matroids on $E$, and characterizing its rank function when it exists.
Toric posets are cyclic analogues of finite posets. They can be viewed combinatorially as equivalence classes of acyclic orientations generated by converting sources into sinks, or geometrically as chambers of toric graphic hyperplane arrangements. I
Motivated by generalizing Khovanovs categorification of the Jones polynomial, we study functors $F$ from thin posets $P$ to abelian categories $mathcal{A}$. Such functors $F$ produce cohomology theories $H^*(P,mathcal{A},F)$. We find that CW posets,
We introduce delta-graphic matroids, which are matroids whose bases form graphic delta-matroids. The class of delta-graphic matroids contains graphic matroids as well as cographic matroids and is a proper subclass of the class of regular matroids. We
We consider the problem of determining the maximum order of an induced vertex-disjoint union of cliques in a graph. More specifically, given some family of graphs $mathcal{G}$ of equal order, we are interested in the parameter $a(mathcal{G}) = min_{G
It follows by Bixbys Lemma that if $e$ is an element of a $3$-connected matroid $M$, then either $mathrm{co}(Mbackslash e)$, the cosimplification of $Mbackslash e$, or $mathrm{si}(M/e)$, the simplification of $M/e$, is $3$-connected. A natural questi