“…There exist several other QMC techniques, in particular the path-integral QMC without phonon integration [40,41], Fourier QMC [21,22], diagrammatic QMC [7,8,42,43,44,45] and Lang-Firsov QMC [46,47,48]. Non-QMC classes of methods include exact diagonalization [49,50,51,52,53,54], variational calculations [13,55,56,57,58,59,60,61,62,63] and the density-matrix renormalization group [64,65,66]. Despite proliferation of methods, most of them have been applied to the two major polaron models: the ionic crystal model of Fröhlich [5] and molecular crystal model of Holstein [67].…”