# Tag Info

Let me give a toy example of the relativization barrier. The canonical example is the time hierarchy theorem that ${\bf TIME}[t(n)] \subsetneq {\bf TIME}[t(n)^2]$. The proof (by diagonalization) is only a little more involved than the proof that the halting problem is undecidable: we define an algorithm $A(x)$ which simulates the $x$th algorithm $A_x$ on ...