Why ETH being false wouldn't make all of NP sub-exponential: reductions add polynomial factors

robleclerc · x · 2026-10-28

LDanilek revisits a complexity-theory intuition: at first it seems that if ETH is false, all NP problems admit sub-exponential algorithms — just reduce any NP problem to NP-complete 3-SAT and solve sub-exponentially. But reductions can introduce polynomial factors: if an NP problem reduces to a cubic-sized 3-SAT, the best known solution remains exponential. The author is relieved for now but suspects more innovation is coming now that the barrier has been breached.

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