Báo cáo toán học: "Holes in graphs" potx

... number of times of obtaining pairs satisfying condition 2 in Claim 2.3, and s 2 is the number of times obtaining pairs satisfying condition 3 in Claim 2.3. Then we obtain a subgraph G (s 1 ,s 2 ) of ... Assuming that H contains no pair satisfying condition 1, we are going to prove that H contains a pair satisfying condition 2. For simplicity, we assume that 1/ is an integer. Since, in...

Ngày tải lên: 07/08/2014, 06:23

... P.L. Hammer. Aggregation of inequalities in integer programming. In P.L. Hammer, E.L. Johnson, B.H. Korte, and G.L. Nemhauser, editors, Studies in Integer Pro- gramming, volume 1 of Annals of ... obtain the same graph, G, after applying σ −1 to G. In other words, by first applying π −1 to ℓ(G) and then applying σ −1 to the result, we obtain the same graph G as we would by simply applyi...

Ngày tải lên: 08/08/2014, 01:20

... =(P, B, I), with point set P,blocksetB and incidence I is a 2-(v,k, λ) design, if |P| = v,everyblockB ∈Bis incident with precisely k points, and every pair of points are together incident with precisely ... non-embeddable.AHadamard 2-design is one in which v =4λ +3, and k =2λ +1. Anincidence matrix ofa2-(v, k, λ)designisab × v matrix A = a ij ,in which a ij =1ifblocki contains point j and...

Ngày tải lên: 07/08/2014, 06:20

... p n points. So one can try to modify the algorithm in order to recognize this class of schemes. Results in this direction will be published in a forthcoming paper. the electronic journal of combinatorics ... an S-ring S if R ∈S.It is clear that an S-ring S is closed under all set-theoretical operations over the subsets belonging to S. An S-ring S  over the group H is an S-subring of an...

Ngày tải lên: 07/08/2014, 06:22

... and we extend it to in nite words by continuity. The in nite fixed point of µ beginning with 0 is denoted by t, hence t = 0110100110010110 ···. The in nite fixed point of µ beginning with 1 is t. ... a finite binary word such that there exists an in nite overlap-free binary sequence which begins with w.Letxbe the lexicographically least in nite overlap-free binary sequence which begins with...

Ngày tải lên: 07/08/2014, 06:22

... contain an induced 6-cycle. Note that the core is invariant under vertex duplications, since the vertex and its twin can be identified by a homomorphism. Generalizing a result of Jin [7], Chen, Jin and ... Math- ematik, No. A 97–16, 1997, to appear in Comb., Prob. and Comp. [3] A. Brouwer, Finite graphs in which the point neighbourhoods are the maximal independent sets, in: From universal...

Ngày tải lên: 07/08/2014, 06:22

... corresponding C-edge by {u, v} and the D-edge by {v, w}. The mixed hypergraph H  we obtain is planar and still has c as a strict t-coloring. Furthermore, in obtaining H  from H, no coloring constraints ... regions in the plane in such a fashion that the vertices correspond to points, where every region contains only those vertices which are in the corresponding edge, and regions onl...

Ngày tải lên: 07/08/2014, 06:22

... combinatorics 8 (2001), #R26 24 for the input graph G. Summarizing we can now state the main result of our paper in the following theorem. Theorem. Geometric circulants can be recognized in time ... the S-ring generated by C,i.e.the smallest S-ring containing C .AnS-ringS  over the group H is an S-subring of S defined overthesamegroupH if S  ⊂S. For a circulant graph G =(X, γ) the S-ring...

Ngày tải lên: 07/08/2014, 06:22

... explained in more detail in Casselman (1994). There is an important difference, however: in the earlier routine, floating point numbers were used to check an inequality involving real roots, in order ... sophisticated programming. In addition to the practical interest in exploring Coxeter groups compu- tationally, there are mathematical problems interesting in their own right invo...

Ngày tải lên: 07/08/2014, 06:23

... one containing x and the other containing y. Note that this implies that there are exactly two [x, y]-bridges in G, since otherwise there is a path in G joining x and y that is disjoint from ... is a path in G(t) −{x, y} joining these ends. Since there is no edge joining x and y in G(T  ) other than f t (e), the claim follows. References [1] Reinhard Diestel, Graph Theory, Springer-V...

Ngày tải lên: 07/08/2014, 08:20