Problems / theoretical-computer-science
theoretical-computer-science / Trace reconstruction; deletion channels
Can worst-case trace reconstruction be done with polynomially many traces?
Theorem 1.1: for fixed s∈(0,1] and 0<c<1/(4log2), Tq,s(n)≥nclog(q3logn) eventually whenever q3logn→∞; so Tq(n)=nΩ(loglogn) at every fixed q, a negative answer to the polynomial question. Theorem 1.2: the minimum total variation between one-trace laws of distinct length-n words is o(n−A) for all A. The companions give a matching-type upper side: quasipolynomial samples and bit complexity with a uniform decoder for known rational retention, and polynomial bounds when q≤n−ε. A gap remains between logT of order lognloglogn (lower) and a power of logn (upper); the exact complexity is not determined.