Dice Question Streamline Icon: https://streamlinehq.com

Triple-iterated logarithm implication from transposition to multiplication

Establish that, in the multitape Turing model, a lower bound Tcost(m) = ω(m log log log m) for binary matrix transposition implies a corresponding lower bound Mcost(m) = ω(m log log log m) for integer multiplication of m-bit integers.

Information Square Streamline Icon: https://streamlinehq.com

Background

The authors present several implications showing that superlinear lower bounds for transposition yield superlinear bounds for multiplication. They prove a sequence of weaker implications (e.g., for O(m log{∘ℓ} m) regimes), but note a gap at the triple-iterated logarithm threshold: they cannot currently show that ω(m log log log m) for transposition forces the same bound for multiplication. Resolving this would sharpen the correspondence between the two problems.

References

For example, if \Tcost(m) = \omega(m \lg \lg \lg m), then we would like to be able to prove that \Mcost(m) = \omega(m \lg \lg \lg m), but we cannot quite manage this.

Integer multiplication is at least as hard as matrix transposition (2503.22848 - Harvey et al., 28 Mar 2025) in Section 1.3 (Summary of main results), immediately before Theorem 1.4