  We discuss the model of a $D$-dimensional confined electron gas in which the
particles are trapped by a harmonic potential. In particular, we study the
non-interacting kinetic and exchange energies of finite-size inhomogeneous
systems, and compare the resulting Thomas-Fermi and Dirac coefficients with
various uniform electron gas paradigms. We show that, in the thermodynamic
limit, the properties of this model are identical to those of the
$D$-dimensional Fermi gas.
