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Log-rank conjecture for deterministic communication complexity

Prove that there exists a universal constant C > 0 such that for every Boolean matrix F, the deterministic communication complexity D(F) satisfies D(F) ≤ C (log(rank(F)))^C, where rank(F) denotes the real rank of F.

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Background

Deterministic protocols partition a Boolean matrix into at most 2{D(F)} monochromatic rectangles, yielding log(rank(F)) ≤ D(F) ≤ rank(F) + 1. The log-rank conjecture posits that the upper bound can be tightened to a polylogarithmic dependence on rank(F), giving a structural characterization of low-rank Boolean matrices via small deterministic communication complexity.

Despite decades of work, the best known upper bounds remain far from polynomial in log(rank(F)), and the conjecture remains a central open problem in communication complexity.

References

The log-rank conjecture speculates that the deterministic communication complexity is polynomially equivalent to the logarithm of the rank. There exists a universal constant $C > 0$ such that for every Boolean matrix $F$, D(F) \le C \left(\log (F)\right)C.

Structure in Communication Complexity and Constant-Cost Complexity Classes (2401.14623 - Hatami et al., 26 Jan 2024) in Conjecture [The log-rank conjecture], Section 2