General neighbour-distinguishing index via chromatic number

AbstractAn edge colouring of a graph G without isolated edges is neighbour-distinguishing if any two adjacent vertices have distinct sets consisting of colours of their incident edges. The general neighbour-distinguishing index of G is the minimum number gndi(G) of colours in a neighbour-distinguishing edge colouring of G. Győri et al. [E. Győri, M. Horňák, C. Palmer, M. Woźniak, General neighbour-distinguishing index of a graph, Discrete Math. 308 (2008) 827–831] proved that gndi(G)∈{2,3} provided G is bipartite and gave a complete characterisation of bipartite graphs according to their general neighbour-distinguishing index. The aim of this paper is to prove that if χ(G)≥3, then ⌈log2χ(G)⌉+1≤gndi(G)≤⌊log2χ(G)⌋+2. Therefore, if log2χ(G)∉Z, then gndi(G)=⌈log2χ(G)⌉+1

Extremális és véletlen struktúrák = Extremal and random structures

Résztvevők: T. Sós Vera, akadémikus, Szemerédi Endre, akadémikus, Füredi Zoltán akadémikus, Győri Ervin, a tudományok doktora, Elek Gábor a tudományok doktora, és témavezetőként Simonovits Miklós (akadémikus). Menetközben csatlakozott a pályázathoz Patkós Balázs. Itt, a rövid beszámolóban csak a legfontosabb témákat említem, Klasszikus Extremális és Ramsey problémák megoldása, ill. ezekkel rokon problémák. A Szemerédi Regularitási Lemma alkalmazásai, az extremális és Ramsey típusú kérdések kapcsolata, ezek kapcsolata a kvázivéletlenséggel, ""tulajdonság-teszteléssel"". Az extrém gráfelmélettel szoros kapcsolatban álló Erdős-Kleitman-Rothschild típusú tételek. A gráflimesz vizsgálata, alkalmazásai Hasonlóságok és különbségek a sűrű és ritka gráfok limesz-elméletében. ,,Sporadikus kérdések,'' pl. algebrai és geometriai alkalmazások. | Project leader: Miklós Simonovits Participants: Vera T. Sós , Endre Szemerédi, Zoltán Füredi, Ervin Győri, Gábor Elek. Balázs Patkós joined our group later. Here I have space only to mention the topics breafly. We were interested primarily in the connection, similarities and differences between deterministic and randomlike structures. Large part of our research was related to the Szemerédi Regularity Lemma and its various versions, and the applications of it, among others, in classical extremal graph and hypergraph problems. We also investigated the application of this lemma in quasi-randomness, property testing, and other related fields. We investigated the graph-limit theory, both for dense and veryy sparse graph sequences. Beside these, we investigated several ``Sporadic question,'' e.g. applications of our methods in algebra and geometry

Graph coloring with cardinality constraints on the neighborhoods

AbstractExtensions and variations of the basic problem of graph coloring are introduced. The problem consists essentially in finding in a graph G a k-coloring, i.e., a partition V1,…,Vk of the vertex set of G such that, for some specified neighborhood Ñ(v) of each vertex v, the number of vertices in Ñ(v)∩Vi is (at most) a given integer hvi. The complexity of some variations is discussed according to Ñ(v), which may be the usual neighbors, or the vertices at distance at most 2, or the closed neighborhood of v (v and its neighbors). Polynomially solvable cases are exhibited (in particular when G is a special tree)

Graph coloring with cardinality constraints on the neighborhoods

Extensions and variations of the basic problem of graph coloring are introduced. The problem consists essentially in finding in a graph a k-coloring, i.e., a partition (V_1,\cdots,V_k) of the vertex set of G such that, for some specified neighborhood \tilde|{N}(v) of each vertex v, the number of vertices in \tilde|{N}(v)\cap V_i is (at most) a given integer h_i^v. The complexity of some variations is discussed according to \tilde|{N}(v), which may be the usual neighbors, or the vertices at distance at most 2, or the closed neighborhood of v (v and its neighbors). Polynomially solvable cases are exhibited (in particular when is a special tree)