Introduction to the theory of continuum polarons

A survey is given of the most important theories on continuum polarons. The concept of a continuum polaron is introduced in an intuitive way. The Fröhlich Hamiltonian is derived and the different approximations are discussed.
The classical polaron treatments are explained or discussed.
The intermediate coupling results are derived starting from an exactly soluble Hamiltionian.
The problem of the relaxed excited states of polarons is treated in the case of strong coupling. Relaxed excited states play an important role in the theory of the optical properties of polarons. Using a simple treatment of the mobility problem a review is given of the experimental situation and some recent developments are indicated.
The problem of the "small polaron" is briefly introduced.