Analytical solution for the deformation of a cylinder under tidal gravitational forces

Quite a few future high precision space missions for testing special and general relativity will employ optical resonators which are used for laser frequency stabilization. These devices are basic for carrying out modern tests of the isotropy of light (Michelson–Morley experiment) and of the universality of the gravitational redshift. As the resonator frequency not only depends on the speed of light but also on the resonator length, the quality of these measurements is very sensitive to elastic deformations of the optical resonator itself. As a consequence, a detailed knowledge about the deformations of the cavity is necessary. Therefore, in this paper, we investigate the modelling of optical resonators in a space environment. Usually, for simulation issues, the finite element method (FEM) is applied in order to investigate the influence of disturbances on resonator measurements. However, for a careful control of the numerical quality of FEM simulations, a comparison with an analytical solution of a simplified resonator model is beneficial. In this paper we present an analytical solution for the problem of an elastic, isotropic, homogeneous free-flying cylinder in space under the influence of a tidal gravitational force. The solution is gained by solving the linear equations of elasticity for special boundary conditions. The applicability of using FEM codes for these simulations shall be verified through the comparison of the analytical solution with the results gained within the FEM code.