  We compute Passarino-Veltman (PV) reduction for tensor loop integrals, that
appear in open field theories. We apply these results to open-Yukawa theory and
compute the self-energy correction of the fields. We found that non-local
divergences show up in the one loop correction to the fermionic self-energy.
These non-local divergences do not disappear even if the tree level theory is
chosen to satisfy the trace preserving condition of the density matrix.
