All-coupling solution for the continuous polaron problem in the Schr\"{o}dinger representation

Abstract

The solution for the large-radius Fr\"{o}hlich polaron in the Schr\"{o}dinger representation of the quantum theory is constructed in the entire range of variation of the coupling constant. The energy and the effective mass of the polaron are calculated by simple algebraic transformations and are analogous to the results found by Feynman on the basis of the variational principle for the path-integrals of this system. It allows us to solve the long-lived problem of the inequalities of the functional and operator approaches for the polaron problem. The developed method is important for other models of particle-field interaction including those ones for which the standard perturbation theory is divergent.