A non-perturbative no-go theorem for photon condensation in approximate modelsG. M. Andolina, F. M. D. Pellegrino, A. Mercurio, O. Di Stefano, M. Polini and S. SavastaEur. Phys. J. Plus, 137 12 (2022) 1348DOI: https://doi.org/10.1140/epjp/s13360-022-03571-0