Critical Casimir force scaling function of the mean spherical model in $2<d<3$ dimensions for nonperiodic boundary conditions

Little is known about finite-size effects of critical systems below the bulk transition temperature $T_c$ for realistic boundary conditions, such as of Dirichlet or Neumann type. However, the exactly solvable mean spherical model can play a significant role in elucidating finite-size effects in the entire scaling regime from above to below $T_c$. We present the first investigation of finite-size effects in this model with nonperiodic boundary conditions for temperatures below $T_c$. To avoid nonscaling effects present in $d=3$ dimensions 1, we continue the model to $2<d