منابع مشابه
Cyclic Ordering Through Partial Orders
The orientation problem for ternary cyclic order relations has been attacked in the literature from combinatorial perspectives, through rotations, and by connection with Petri nets. We propose here a two-fold characterization of orientable cyclic orders in terms of symmetries of partial orders as well as in terms of separating sets (cuts). The results are inspired by properties of non-sequentia...
متن کاملCyclic orders: Equivalence and duality
Cyclic orders of graphs and their equivalence have been promoted by Bessy and Thomassés recent proof of Gallai’s conjecture. We explore this notion further : we prove that two cyclic orders are equivalent if and only if the winding number of every circuit is the same in the two. The proof is short and provides a good characterization and a polynomial algorithm for deciding whether two orders ar...
متن کاملFinding coherent cyclic orders in strong digraphs
A cyclic order in the vertex set of a digraph is said to be coherent if any arc is contained in a directed cycle whose winding number is one. This notion plays a key role in the proof by Bessy and Thomassé (2004) of a conjecture of Gallai (1964) on covering the vertex set by directed cycles. This paper presents an efficient algorithm for finding a coherent cyclic order in a strongly connected d...
متن کاملOn Cyclic Orders and Synchronisation Graphs
We use a dedicated quotient operation called winding to give a new characterization of orientable cyclic orders; the characterization is twofold, in terms of partial orders and of separation properties. For this, we show the application to Petri nets: by winding causal nets, one obtains cyclic orders on synchronization graph that yield live and safe markings and describe the concurrent behavior...
متن کاملCyclic orders on the quantum grassmannian
The quantum grassmannian is known to be a graded quantum algebra with a straightening law when the poset of generating quantum minors is endowed with the standard partial ordering. In this paper it is shown that this result remains true when the ordering is subjected to cyclic shifts. The method involves proving that noncommutative dehomogenisation is possible at any consecutive quantum minor. ...
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ژورنال
عنوان ژورنال: European Journal of Combinatorics
سال: 1989
ISSN: 0195-6698
DOI: 10.1016/s0195-6698(89)80022-8