scholarly journals On Subgraphs Induced by Transversals in Vertex-Partitions of Graphs

10.37236/1062 ◽  
2006 ◽  
Vol 13 (1) ◽  
Author(s):  
Maria Axenovich

For a fixed graph $H$ on $k$ vertices, we investigate the graphs, $G$, such that for any partition of the vertices of $G$ into $k$ color classes, there is a transversal of that partition inducing $H$. For every integer $k\geq 1$, we find a family ${\cal F}$ of at most six graphs on $k$ vertices such that the following holds. If $H\notin {\cal F}$, then for any graph $G$ on at least $4k-1$ vertices, there is a $k$-coloring of vertices of $G$ avoiding totally multicolored induced subgraphs isomorphic to $H$. Thus, we provide a vertex-induced anti-Ramsey result, extending the induced-vertex-Ramsey theorems by Deuber, Rödl et al.

2010 ◽  
Vol 38 (1-2) ◽  
pp. 100-120 ◽  
Author(s):  
József Balogh ◽  
Jane Butterfield

2014 ◽  
Vol 06 (03) ◽  
pp. 1450043
Author(s):  
Bo Ning ◽  
Shenggui Zhang ◽  
Bing Chen

Let claw be the graph K1,3. A graph G on n ≥ 3 vertices is called o-heavy if each induced claw of G has a pair of end-vertices with degree sum at least n, and called 1-heavy if at least one end-vertex of each induced claw of G has degree at least n/2. In this note, we show that every 2-connected o-heavy or 3-connected 1-heavy graph is Hamiltonian if we restrict Fan-type degree condition or neighborhood intersection condition to certain pairs of vertices in some small induced subgraphs of the graph. Our results improve or extend previous results of Broersma et al., Chen et al., Fan, Goodman and Hedetniemi, Gould and Jacobson, and Shi on the existence of Hamilton cycles in graphs.


2008 ◽  
Vol 23 (1) ◽  
pp. 120-126
Author(s):  
Ze-min Jin ◽  
Xue-liang Li

2019 ◽  
Vol 76 ◽  
pp. 53-61 ◽  
Author(s):  
Maria Chudnovsky ◽  
Alex Scott ◽  
Paul Seymour

2010 ◽  
Vol 310 (4) ◽  
pp. 742-747 ◽  
Author(s):  
Y. Caro ◽  
R. Yuster

10.37236/2882 ◽  
2013 ◽  
Vol 20 (1) ◽  
Author(s):  
Raphael Yuster

Let $h$ be a given positive integer. For a graph with $n$ vertices and $m$ edges, what is the maximum number of pairwise edge-disjoint {\em induced} subgraphs, each having  minimum degree at least $h$? There are examples for which this number is $O(m^2/n^2)$. We prove that this bound is achievable for all graphs with polynomially many edges. For all $\epsilon > 0$, if $m \ge n^{1+\epsilon}$, then there are always $\Omega(m^2/n^2)$ pairwise edge-disjoint induced subgraphs, each having  minimum degree at least $h$. Furthermore, any two subgraphs intersect in an independent set of size at most $1+ O(n^3/m^2)$, which is shown to be asymptotically optimal.


10.37236/976 ◽  
2007 ◽  
Vol 14 (1) ◽  
Author(s):  
Tomás Feder ◽  
Pavol Hell ◽  
Wing Xie

Each $m$ by $m$ symmetric matrix $M$ over $0, 1, *$, defines a partition problem, in which an input graph $G$ is to be partitioned into $m$ parts with adjacencies governed by $M$, in the sense that two distinct vertices in (possibly equal) parts $i$ and $j$ are adjacent if $M(i,j)=1$, and nonadjacent if $M(i,j)=0$. (The entry $*$ implies no restriction.) We ask which matrix partition problems admit a characterization by a finite set of forbidden induced subgraphs. We prove that matrices containing a certain two by two diagonal submatrix $S$ never have such characterizations. We then develop a recursive technique that allows us (with some extra effort) to verify that matrices without $S$ of size five or less always have a finite forbidden induced subgraph characterization. However, we exhibit a six by six matrix without $S$ which cannot be characterized by finitely many induced subgraphs. We also explore the connection between finite forbidden subgraph characterizations and related questions on the descriptive and computational complexity of matrix partition problems.


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