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If lower bound of a problem is exponential then is it NP?

Submitted by: @import:stackexchange-cs··
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problemboundlowerexponentialthen

Problem

Assuming that we have a problem $p$ and we showed that the lower bound for solving $p$ is $\mathcal{\Omega}(2^n)$.

  • can lower bound $\mathcal{\Omega}(2^n)$ implies the problem in $NP$?

Solution

No. For example, the halting problem has an $\Omega(2^n)$ lower bound, but it is not in NP (since it is not computable).

The nondeterministic time hierarchy theorem shows that any NEXP-complete problem is another example (with $2^n$ potentially replaced by a smaller exponential function $c^{n^\epsilon}$).

NP is an upper bound on the complexity of a problem.

Context

StackExchange Computer Science Q#98277, answer score: 21

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