  We have studied the low energy spin dynamics between 4.6K and 0.07K in a
Tb2Ti2O7 single crystal sample, by means of inelastic neutron scattering
experiments. The spectra consist in a dual response, with a static and an
inelastic contribution, showing striking Q-dependences. We propose an
interpretation involving an anisotropic exchange interaction in combination
with a breaking of the threefold symmetry at the rare earth site. Simulations
of the Q-dependent scattering in the Random Phase Approximation account well
for the inelastic response.
