Negativity of the Casimir Self-Entropy in Spherical Geometries

It has been recognized for some time that, even perfect conductors, the interaction Casimir entropy, due to quantum/thermal fluctuations, can be negative. This result was not considered problematic because it thought that self-entropies of bodies would cancel this negative yielding a total entropy positive. In fact, cancellation seems occur. The positive self-entropy perfectly conducting sphere does indeed just system consisting and plate, but model with weaker coupling in general possesses regime where appears. physical meaning surprising remains obscure. paper, we re-examine these issues, using improved mathematical techniques, partly based on Abel–Plana formula, present numerical results arbitrary temperatures couplings, which exhibit same remarkable features.