  Nuclear mass autocorrelations are investigated as a function of the number of
nucleons. The fluctuating part of these autocorrelations is modeled by a
parameter free model in which the nucleons are confined in a rigid sphere.
Explicit results are obtained by using periodic orbit theory. Despite the
simplicity of the model we have found a remarkable quantitative agreement of
the mass autocorrelations for all nuclei in the nuclear data chart. In order to
achieve a similar degree of agreement for the nuclear masses themselves it is
necessary to consider additional variables such as multipolar corrections to
the spherical shape and an effective number of nucleons. Our findings suggest
that higher order effects like nuclear deformations or residual interactions
have little relevance in the description of the fluctuations of the nuclear
autocorrelations.
