  Within the last decade, artificially engineered Bose Einstein Condensation
has been achieved in atomic systems. Bose Einstein Condensates are superfluids
just like bosonic Helium is and all interacting bosonic fluids are expected to
be at low enough temperatures. One difference between the two systems is that
superfluid Helium exhibits roton excitations while Bose Einstein Condensates
have never been observed to have such excitations. The reason for the roton
minimum in Helium is its proximity to a solid phase. The roton minimum is a
consequence of enhanced density fluctuations at the reciprocal lattice vector
of the stillborn solid. Bose Einstein Condensates in atomic traps are not near
a solid phase and therefore do not exhibit roton minimum. We conclude that if
Bose Einstein Condensates in an optical lattice are tuned near a transition to
a Mott insulating phase, a roton minimum will develop at a reciprocal lattice
vector of the lattice. Equivalently, a peak in the structure factor will appear
at such a wavevector. The smallness of the roton gap or the largeness of the
structure factor peak are experimental signatures of the proximity to the Mott
transition.
