Compact Distributed Interactive Proofs for the Recognition of Cographs and Distance-Hereditary Graphs
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 π½π π¬ protocol with a proof size of πͺ(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 π½π π¬ with certificates of size πͺ(log n). Second, we give a three-round, π½π¬π π¬ interactive protocol for the recognition of distance-hereditary graphs, still with a proof size of πͺ(log n) bits and also using shared randomness. Finally, we show that any one-round (denoted π½π¬) or two-round, π½π¬π protocol for the recognition of cographs or distance-hereditary graphs requires certificates of size Ξ©(log n) bits. Moreover, we show that any constant-round π½π π¬ protocol using shared randomness requires certificates of size Ξ©(loglog n).
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