Orderability form selections: Another solution to the orderability problem
نویسندگان
چکیده
منابع مشابه
Adjacency, Inseparability, and Base Orderability in Matroids
Two elements in an oriented matroid are inseparable if they have either the same sign in every signed circuit containing them both or opposite signs in every signed circuit containing them both. Two elements of a matroid are adjacent if there is no M(K4)-minor using them both, and in which they correspond to a matching of K4. We prove that two elements e, { of an oriented matroid are inseparabl...
متن کاملDiagram Groups, Braid Groups, and Orderability
We prove that all diagram groups (in the sense of Guba and Sapir) are left-orderable. The proof is in two steps: firstly, it is proved that all diagram groups inject in a certain braid group on infinitely many strings, and secondly, this group is then shown to be left-orderable.
متن کاملBichromatic P4-composition schemes for perfect orderability
A P4 is an induced path with four vertices. A bichromatic P4 composition scheme is as follows: (1) start with two graphs with vertex sets of di1erent colour, say black • and white ◦, (2) select a set of allowable four-vertex bichromatic sequences, for example {• • ••; ◦ ◦ ◦◦; • ◦ ◦•; ◦ • •◦}, (3) add edges between the graphs so that in the composed graph each P4 is coloured with an allowable se...
متن کاملOn the Closed-Form Solution of a Nonlinear Difference Equation and Another Proof to Sroysang’s Conjecture
The purpose of this paper is twofold. First we derive theoretically, using appropriate transformation on x(n), the closed-form solution of the nonlinear difference equation x(n+1) = 1/(±1 + x(n)), n ∈ N_0. The form of solution of this equation, however, was first obtained in [10] but through induction principle. Then, with the solution of the above equation at hand, we prove a case ...
متن کاملMeyniel Weakly Triangulated Graphs - I: Co-perfect Orderability
We show that Meyniel weakly triangulated graphs are co-perfectly orderable (equivalently , that P 5-free weakly triangulated graphs are perfectly orderable). Our proof is algorithmic, and relies on a notion concerning separating sets, a property of weakly triangulated graphs, and several properties of Meyniel weakly triangulated graphs.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Fundamenta Mathematicae
سال: 1984
ISSN: 0016-2736,1730-6329
DOI: 10.4064/fm-121-3-219-229