Laplace equations on the fractal cubes and Casimir effect Alireza Khalili Golmankhaneh and Safa Measoomy Nia Eur. Phys. J. Spec. Top., 230 21-22 (2021) 3895-3900 Published online: 09 November 2021 DOI: 10.1140/epjs/s11734-021-00317-4