We prove Ramsey-type results for intersection graphs of geometric objects the plane. In particular, we prove the following bounds, all of which are tight apart from the constant c. There is a constant c > 0 such that for every family F of n ≥ 2 convex sets in the plane, the intersection graph of F or its complement contains a balanced complete bipartite graph of size at least cn. There is a con...

Abstract For a fixed infinite graph $H$ , we study the largest density of monochromatic subgraph isomorphic to that can be found in every two-colouring edges $K_{\mathbb{N}}$ . This is called Ramsey upper and was introduced by Erdős Galvin restricted setting, DeBiasio McKenney general. Recently [4], path determined. Here, find value this for all locally finite graphs up factor 2, answering ques...

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii PRELIMINARIES AND NOTATION . . . . . . . . . . . . . . . . . . . . . ix CHAPTER 1. OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 The Graph Ramsey Number . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1 Arrow Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 The Dir...

For graphs F and H, we say F is Ramsey for H if every 2-coloring of the edges of F contains a monochromatic copy of H. The graph F is Ramsey H-minimal if F is Ramsey for H and there is no proper subgraph F ′ of F so that F ′ is Ramsey for H. Burr, Erdős, and Lovász defined s(H) to be the minimum degree of F over all Ramsey H-minimal graphs F . Define Ht,d to be a graph on t + 1 vertices consist...

the concept of the bipartite divisor graph for integer subsets has been considered in [‎graph combinator., ‎ 26 (2010) 95--105‎.]. ‎in this paper‎, ‎we will consider this graph for the set of character degrees of a finite group $g$ and obtain some properties of this graph‎. ‎we show that if $g$ is a solvable group‎, ‎then the number of connected components of this graph is at most $2$ and if $g...

We characterize the completely determined Borel subsets of HYP as exactly [Formula: see text] HYP. As a result, believes there is well-ordering reals, that Dual Ramsey Theorem fails, and every d-regular bipartite graph has perfect matching, among other examples. Therefore, several theorems descriptive combinatorics are not theories hyperarithmetic analysis. In case Theorem, this answers questio...

Consider the following game between two players, Builder and Painter. Builder draws edges one at a time and Painter colours them, in either red or blue, as each appears. Builder’s aim is to force Painter to draw a monochromatic copy of a fixed graph G. The minimum number of edges which Builder must draw, regardless of Painter’s strategy, in order to guarantee that this happens is known as the o...