  New channel coding converse and achievability bounds are derived for a single
use of an arbitrary channel. Both bounds are expressed using a quantity called
the "smooth 0-divergence", which is a generalization of Renyi's divergence of
order 0. The bounds are also studied in the limit of large block-lengths. In
particular, they combine to give a general capacity formula which is equivalent
to the one derived by Verdu and Han.
