The Bandwidth Theorem in Sparse Graphs

TL;DR

This paper extends the bandwidth theorem to sparse and pseudorandom graphs, showing that certain subgraphs with bounded degree and bandwidth are contained in these graphs under specific conditions.

Contribution

It provides the first resilience results in pseudorandom graphs for a broad class of spanning subgraphs, including trees and graphs with small degeneracy.

Findings

Contains all k-colourable graphs with bounded degree and bandwidth in sparse random graphs.

Establishes resilience results for pseudorandom graphs with respect to spanning subgraphs.

Improves conditions for containing spanning bounded degree trees in sparse random graphs.

Abstract

The bandwidth theorem [Mathematische Annalen, 343(1):175--205, 2009] states that any $n$-vertex graph $G$ with minimum degree $\big(\tfrac{k-1}{k}+o(1)\big)n$ contains all $n$-vertex $k$-colourable graphs $H$ with bounded maximum degree and bandwidth $o(n)$. We provide sparse analogues of this statement in random graphs as well as pseudorandom graphs. More precisely, we show that for $p\gg \big(\tfrac{\log n}{n}\big)^{1/\Delta}$ asymptotically almost surely each spanning subgraph $G$ of $G(n,p)$ with minimum degree $\big(\tfrac{k-1}{k}+o(1)\big)pn$ contains all $n$-vertex $k$-colourable graphs $H$ with maximum degree $\Delta$, bandwidth $o(n)$, and at least $C p^{-2}$ vertices not contained in any triangle. A similar result is shown for sufficiently bijumbled graphs, which, to the best of our knowledge, is the first resilience result in pseudorandom graphs for a rich class of spanning subgraphs. Finally, we provide improved results for $H$ with small degeneracy, which in particular imply a resilience result in $G(n,p)$ with respect to the containment of spanning bounded degree trees for $p\gg \big(\tfrac{\log n}{n}\big)^{1/3}$.