Linear-Time Multitape Turing Machine Multiplication
Determine whether there exists a multitape Turing machine that multiplies two n-bit integers in O(n) time and correctly solves MULT_n on all n-bit inputs.
References
It is an open problem whether there exists an $O(n)$-time MTM which correctly solves $\MULT_n$ on all instances with parameter $n$ \citep{Afshani19}.
— New Techniques for Constructing Rare-Case Hard Functions
(2411.09597 - Nareddy et al., 14 Nov 2024) in Section 1 (Introduction)