Goldmann and Russell (2002) initiated the study of the complexity of the equation satisfiability problem in finite groups by showing that it is in P for nilpotent groups while it is NP-complete for non-solvable groups. Since then, several results have appeared showing that the problem can be solved in polynomial time in certain solvable groups of Fitting length two. In this work, we present the first lower bounds for the equation satisfiability problem in finite solvable groups: under the assumption of the exponential time hypothesis, we show that it cannot be in P for any group of Fitting length at least four and for certain groups of Fitting length three. Moreover, the same hardness result applies to the equation identity problem.
ACM Subject Classification Theory of computation → Problems, reductions and completeness
Keywords and phrases equations in groups, solvable groups, exponential time hypothesisFunding Armin Weiß: Funded by DFG project DI 435/7-1.Acknowledgements I am grateful to Moses Ganardi for bringing my attention to the AND-weakness conjecture and pointing out the relation to the exponential time hypothesis. I am also thankful to David A. Mix Barrington for an interesting email exchange concerning the AND-weakness conjecture and the idea to include steps of the lower central series in Proposition 8 to get a more refined upper bound. Finally, I want to thank Caroline Mattes and Jan Philipp Wächter for many helpful discussions.