The renormalization of the most general dimension-six four-fermion operators
without power subtractions is studied at one loop in lattice perturbation
theory using overlap fermions. As expected, operators with different chirality
do not mix among themselves and parity-conserving and parity-violating
multiplets renormalize in the same way. The renormalization constants of
unimproved and improved operators are also the same. These mixing factors are
necessary to determine physical matrix elements relevant to many
phenomenological applications of weak interactions. The most important are the
K0-K0bar and B0-B0bar mixings in the Standard Model and beyond, the Delta I
=1/2 rule and epsilon'/epsilon.Comment: Latex, 24 pages, 1 figure include
