Compact Distributed Interactive Proofs for the Recognition of Cographs and Distance-Hereditary Graphs

TL;DR

This paper introduces compact distributed interactive proof protocols for recognizing cographs and distance-hereditary graphs, achieving efficient verification with minimal proof sizes and establishing lower bounds for protocols with fewer rounds.

Contribution

It presents the first two-round distributed interactive proof for cograph recognition and a three-round protocol for distance-hereditary graphs, with tight bounds on proof sizes.

Findings

Two-round dAM protocol for cographs with O(log n) proof size

Three-round dMAM protocol for distance-hereditary graphs with O(log n) proof size

Lower bounds on proof size for protocols with fewer rounds

Abstract

We present compact distributed interactive proofs for the recognition of two important graph classes, well-studied in the context of centralized algorithms, namely complement reducible graphs and distance-hereditary graphs. Complement reducible graphs (also called cographs) are defined as the graphs not containing a four-node path $P_4$ as an induced subgraph. Distance-hereditary graphs are a super-class of cographs, defined as the graphs where the distance (shortest paths) between any pair of vertices is the same on every induced connected subgraph. First, we show that there exists a distributed interactive proof for the recognition of cographs with two rounds of interaction. More precisely, we give a $\mathsf{dAM}$ protocol with a proof size of $\mathcal{O}(\log n)$ bits that uses shared randomness and recognizes cographs with high probability. Moreover, our protocol can be adapted to verify any Turing-decidable predicate restricted to cographs in $\mathsf{dAM}$ with certificates of size $\mathcal{O}(\log n)$. Second, we give a three-round, $\mathsf{dMAM}$ interactive protocol for the recognition of distance-hereditary graphs, still with a proof size of $\mathcal{O}(\log n)$ bits and also using shared randomness. Finally, we show that any one-round (denoted $\mathsf{dM}$) or two-round, $\mathsf{dMA}$ protocol for the recognition of cographs or distance-hereditary graphs requires certificates of size $\Omega(\log n)$ bits. Moreover, we show that any constant-round $\mathsf{dAM}$ protocol using shared randomness requires certificates of size $\Omega(\log \log n)$.