  We formulate an effective low energy theory for the fermionic excitations in
d-wave superconductors in the presence of periodic vortex lattices. These can
be modeled by an effective free Dirac Hamiltonian with renormalized velocities
and possibly a small mass term. In the presence of random nonmagnetic
impurities this will result in universal (i.e. field and disorder strength
independent) thermal and spin conductivities with values different from those
occurring in the Meissner state.
