If we have a $2^{n^a}$ algorithm to $K$-$SAT$ where $a<1$ for all $K>2$ then $ETH$ fails and literature gives consequences. What are the consequences if $a=o(1)$?

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    $\begingroup$ The title and question don't match. The assertion that there is no $2^{n^a}$-time algorithm for $k$-SAT with $a = o(1)$ is a weaker statement than ETH. $\endgroup$ Commented Nov 20, 2019 at 16:02
  • $\begingroup$ $2^{n^{1/\log\log n}}$ falls under $2^{n^{o(1)}}$ while $2^{n^{0.99999}}$ falls under $2^{n^a}$ with $a<1$. $\endgroup$
    – VS.
    Commented Nov 20, 2019 at 16:15
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    $\begingroup$ Yes, and $2^{n^{1/\log \log n}} = o(2^{n^{0.9999}})$, so asserting that there is no $2^{n^{1/\log \log n}}$-time algorithm for $k$-SAT is weaker than asserting that there is no $2^{n^{0.9999}}$-time algorithm. $\endgroup$ Commented Nov 20, 2019 at 16:27
  • $\begingroup$ Is this question sort of the same? cstheory.stackexchange.com/questions/9237/… $\endgroup$ Commented Nov 20, 2019 at 20:27
  • $\begingroup$ ETH is related to 3-SAT, but not for k-SAT [the SETH is related to k-SAT with different definition than ETH] $\endgroup$
    Commented Nov 22, 2019 at 10:50

1 Answer 1


If $\alpha \in O\left(\frac{\log\log n}{ \log n}\right)$, then you would have proved that $P = NP$, since $n^{\alpha} \in O(\log n)$ and $2^{n^{\alpha}} \in O(\mathrm{poly}(n))$.

On the other hand, for $\alpha \in \omega\left(\frac{\log\log n}{ \log n}\right)$ and $\alpha \in o(1)$, I think the most interesting thing that happens is breaking ETH with all its consequences (including breaking SETH and many other conditional lower-bounds on polynomial and parameterized problems).

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    $\begingroup$ You mean $\alpha \in \omega (\frac{\log \log n}{\log n})$ $\endgroup$
    – Saeed
    Commented Mar 22, 2020 at 10:20

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