Would physical laws permit the construction of computing machines
that are capable of solving some problems much faster than the
standard computational model? Recent evidence suggests that this
might be the case in the quantum world. But the question is of
great interest even in the realm of classical physics. ... more >>>

We give evidence for a stronger version of the extended Church-Turing thesis: among the set of physically possible computers, there are computers that can simulate any other realizable computer with only additive constant overhead in space, time, and other natural resources. Complexity-theoretic results that hold for these computers can therefore ... more >>>