Kinetic energy of a trapped Fermi gas interacting with a Bose-Einstein condensate

We study a confined mixture of bosons and fermions in the regime of quantal degeneracy, with particular attention to the effects of the interactions o n the kinetic energy of the fermionic component. We are able to explore a w ide region of system parameters by identifying two scaling variables which completely determine its state at low temperature. These are the ration of the boson-fermion and boson-boson interaction strengths and the ratio of th e radii of the two clouds. We find that the effect of the interactions can be sizeable for reasonable choices of the parameters and that its experimen tal study can be used to infer the sign of the boson-fermion scattering len gth. The interplay between interactions and thermal effects in the fermioni c kinetic energy is also discussed.