EJC
2007
13 years 9 months ago
2007
Consider a polar space S weakly embedded in a projective space P. A secant of S is the intersection of the point set of S with a line of P spanned by two non-collinear points of S...
EJC
2007
13 years 9 months ago
2007
In [2], we showed the existence of five isomorphism classes of hyperplanes in each dual polar space of type DH(5, q2). We also proved there that every hyperplane of DH(5, q2) bel...
EJC
2007
13 years 9 months ago
2007
We construct algorithms for deciding essentially any minor-closed parameter, with explicit time bounds. This result strengthens previous results by Robertson and Seymour [1,2], Fr...
EJC
2007
13 years 9 months ago
2007
We prove that the translation plane and the shift plane defined by a planar partition function form an oval pair of projective planes in the sense that the planes share a line pe...
EJC
2007
13 years 9 months ago
2007
We develop a theory of representations in Rm for directed strongly regular graphs, which gives a new proof of a nonexistence condition of Jørgensen [8]. We also describe some new...
EJC
2007
13 years 9 months ago
2007
EJC
2007
13 years 9 months ago
2007
It was conjectured by Thomassen ([B. Alspach, C. Godsil, Cycle in graphs, Ann. Discrete Math. 27 (1985)], p. 466) that every longest circuit of a 3-connected graph must have a cho...
EJC
2007
13 years 9 months ago
2007
We examine the binary codes obtained from the row span over the field F2 of an adjacency matrix of the rectangular lattice graphs L2(m, n) for 3 ≤ m < n and show that permut...
EJC
2007
13 years 9 months ago
2007
We consider in this work the enumeration of involutions by descent sets, and based on that, by descent numbers. Formulas of the number of involutions with a prescribed descent set...
EJC
2007
13 years 9 months ago
2007
: We show that the complexity of a cutting word u in a regular tiling by a polyomino Q is equal to Pn(u) = (p+q−1)n+1 for all n ≥ 0, where Pn(u) counts the number of distinct f...