  We want to study the Casimir effect for a single conducting microscopic
cylindrical cavity. The mathematical technique is based on the Green function
of the geometry of the inside of the cavity, and the integral regularization is
based on the plasma frequency cutoff for real conductors. Using the symmetric
electromagnetic energy-momentum tensor, in terms of four potential, the total
Casimir energy for the inside of the Cavity is calculated. Neglecting the
contribution of the external (outside of the cavity) Casimir energy based on
the reason recently presented in [1], the forces experienced by the lateral
surface of the cavity and its circular bases are calculated. The resulting
expressions show that these forces are repulsive. The numerical computation is
done for the real problem of a cavity with a basis of a radius in the same
order of its height at the scale of 100 nanometers made of the best conducting
materials already known.
