Compact Distributed Interactive Proofs for the Recognition of Cographs and Distance-Hereditary Graphs
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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 𝖽𝖠𝖬 protocol with a proof size of 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 𝖽𝖠𝖬 with certificates of size 𝒪(log n). Second, we give a three-round, 𝖽𝖬𝖠𝖬 interactive protocol for the recognition of distance-hereditary graphs, still with a proof size of 𝒪(log n) bits and also using shared randomness. Finally, we show that any one-round (denoted 𝖽𝖬) or two-round, 𝖽𝖬𝖠 protocol for the recognition of cographs or distance-hereditary graphs requires certificates of size Ω(log n) bits. Moreover, we show that any constant-round 𝖽𝖠𝖬 protocol using shared randomness requires certificates of size Ω(loglog n).
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