Abstract

AbstractA perfect Kr‐tiling in a graph G is a collection of vertex‐disjoint copies of Kr that together cover all the vertices in G. In this paper we consider perfect Kr‐tilings in the setting of randomly perturbed graphs; a model introduced by Bohman, Frieze, and Martin [7] where one starts with a dense graph and then adds m random edges to it. Specifically, given any fixed we determine how many random edges one must add to an n‐vertex graph G of minimum degree to ensure that, asymptotically almost surely, the resulting graph contains a perfect Kr‐tiling. As one increases we demonstrate that the number of random edges required “jumps” at regular intervals, and within these intervals our result is best‐possible. This work therefore closes the gap between the seminal work of Johansson, Kahn and Vu [25] (which resolves the purely random case, that is, ) and that of Hajnal and Szemerédi [18] (which demonstrates that for the initial graph already houses the desired perfect Kr‐tiling).

Highlights

  • A significant facet of both extremal graph theory and random graph theory is the study of embeddings

  • Note that a perfect H-tiling is a generalization of the notion of a perfect matching; perfect matchings correspond to the case when H is a single edge

  • For every fixed graph H they determined how many random edges one must add to a graph G of linear minimum degree to ensure that a.a.s

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Summary

INTRODUCTION

A significant facet of both extremal graph theory and random graph theory is the study of embeddings. In the setting of random graphs, one is interested in the threshold for the property that G(n, p) asymptotically almost surely (a.a.s.) contains a fixed (spanning) subgraph F. A classical line of inquiry in extremal graph theory is to determine the minimum degree threshold that ensures a graph G contains a fixed (spanning) subgraph F. A much studied problem in both the extremal and random settings concerns the case when F is a so-called perfect H-tiling. In this paper we bridge the gap between the random and extremal models for the problem of perfect clique tilings

Perfect tilings in graphs
Perfect tilings in random graphs
The model of randomly perturbed graphs
NOTATION AND PRELIMINARIES
A deterministic tiling result
Regularity
Supersaturation
Subgraph counts in random graphs
AN ALMOST PERFECT TILING
THE ABSORPTION
The absorbing structure—deterministic edges
Reachability
Absorbing gadgets
The absorbing structure—random edges
Defining an absorbing structure
The existence of an absorbing structure
CONCLUDING REMARKS
Full Text
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