Are all NP-complete languages log-space reducible to each other?
Wikipedia makes the following points:


It is unknown whether all NP-complete languages are NP-complete also with respect to logspace reductions.
However, "all known" NP-complete languages are NP-complete also with respect to logspace reductions.
There are some hints that a weaker class of reductions, AC0 reductions, may result in a different notion of NP-completeness.