  We analyze 2-point functions in the relativistic Bose gas on the lattice,
i.e., a charged scalar phi-4 field with chemical potential mu. Using a
generalized worm algorithm we perform a Monte Carlo simulation in a dual
representation in terms of fluxes where the complex action problem is overcome.
We explore various aspects of lattice spectroscopy at finite density and zero
temperature, such as the asymmetry of forward and backward propagation in time
and the transition into the condensed phase. It is shown that after a suitable
subtraction the exponents for forward and backward propagation are independent
of mu and agree with the mass obtained from the propagator at mu = 0. This
holds for mu < mu_c and shows that below the condensation transition the mass
is independent of mu as expected from the Silver Blaze scenario.
