One-sided-error completeness for BPP
Determine whether every constant-cost randomized two-party communication problem (the class BPP in the paper’s sense) can be computed by a constant-cost deterministic oracle protocol that makes a constant number of queries to constant-cost one-sided-error communication problems (the class RP^0).
References
All known problems in BPP can be solved with (1) queries to constant-cost problems with one-sided error (ie the class RP0). Is this always true? (See also [HH24]). We mentioned above that finding a complete problem (or hierarchy) could have answered many questions about BPP (depending on the properties of the complete problem itself); these two open problems are examples of that.
— Constant-Cost Communication is not Reducible to k-Hamming Distance
(2407.20204 - Fang et al., 29 Jul 2024) in Section 1.5 (Constant-Cost Communication: the Story so Far and Farther), paragraph “One-sided error, and large rectangles.”