Any fully graphic region of degree sequences can be sampled rapidly

Abstract

Let $n>c_1\ge c_2$ and $Σ$ be positive integers with $n\cdot c_1\ge Σ\ge n\cdot c_2.$ Let $\mD=\dds{n}Σ{c_1}{c_2}$ denote the set of all degree sequences of length $n$ with the even sum $Σ$ and satisfying $c_1\ge d_i\ge c_2.$ We show that if all degree sequences in $\mD$ are graphic, then $\mD$ is $3n^{13}$-stable. (The concept of $P$-stability was introduced by Jerrum and Sinclair in 1990.) In particular, this implies that the switch Markov-chain mixes rapidly on all such degree sequences. In this paper we also study the inverse direction. We show the following: if all graphic sequences of a degree sequence region satisfy the $p(n)$-stability condition then the overwhelming majority of the sequences in the region is graphic. This answers affirmatively a question raised in the paper \DOI{10.1016/j.aam.2024.102805}.