  We study some aspects of short-distance interaction between parallel
D3-branes in type 0 string theory as described by the corresponding
world-volume gauge theory. We compute the one-loop effective potential in the
non-supersymmetric SU(N) x SU(N) gauge theory (which is a Z_2 projection of the
U(2N) n=4 SYM theory) representing dyonic branes composed of N electric and N
magnetic D3-branes. The branes of the same type repel at short distances, but
an electric and a magnetic brane attract, and the forces between self-dual
branes cancel. The self-dual configuration (with the positions of the electric
and the magnetic branes, i.e. the diagonal entries of the adjoint scalar
fields, being the same) is stable against separation of one electric or one
magnetic brane, but is unstable against certain modes of separation of several
same-type branes. This instability should be suppressed in the large N limit,
i.e. should be irrelevant for the large N CFT interpretation of the gauge
theory suggested in hep-th/9901101.
