Problem 42
Show the error in the following fallacious “proof” that P ( NP.
Proof by contradiction. Assume that P = NP. Then SAT ( P. So, of some
k, SAT ( TIME(nk). Because every language in NP is polynomial time
reducible to SAT, NP ( TIME(nk). Therefore P ( TIME(nk). But, by the
time hierarchy theorem, TIME(nk+1) contains a language which isn’t in
TIME(nk), which contradicts P ( TIME(nk). Therefore P ( NP.
