  The paper derives the transverse forces (the Magnus and the Lorentz forces)
in the lattice models of superfluids in the continuous approximation. The
continuous approximation restores translational invariance absent in the
original lattice model, but the theory is not Galilean invariant. As a result,
calculation of the two transverse forces on the vortex, Magnus force and
Lorentz force, requires the analysis of two balances, for the true momentum of
particles in the lattice (Magnus force) and for the quasimomentum (Lorentz
force) known from the Bloch theory of particles in the periodic potential.
While the developed theory yields the same Lorentz force, which was well known
before, a new general expression for the Magnus force was obtained. The theory
demonstrates how a small Magnus force emerges in the Josephson-junction array
if the particle-hole symmetry is broken. The continuous approximation for the
Bose--Hubbard model close to the superfluid-insulator transition was developed,
which was used for calculation of the Magnus force. The theory shows that there
is an area in the phase diagram for the Bose--Hubbard model, where the Magnus
force has an inverse sign with respect to that which is expected from the sign
of velocity circulation.
