Ultraviolet sensitivity of Casimir energy

We quantitatively estimate the effect of ultraviolet (UV) physics on the Casimir energy in a five-dimensional (5D) model on S1/Z2. If the cutoff scale of the 5D theory is not far from the compactification scale, the UV physics may affect the low-energy result. We work in the cutoff regularization scheme by introducing two independent cutoff scales for the spatial momentum in the non-compact space and for the Kaluza-Klein masses. The effects of the UV physics are incorporated as a damping effect of the contributions to the vacuum energy around the cutoff scales. We numerically calculate the Casimir energy and evaluate the deviation from the result obtained in the zeta-function regularization, which does not include information on the UV physics. We find that the result agrees well with the latter for Gaussian-type damping, while it can deviate for kink-type damping.