NONLINEAR ENERGY LOCALIZATION AND MELTING

We discuss nonlinear effects which could be the basis for a theory of melting involving processes by which energy, initially evenly distribu ted in a lattice, can localize itself into large amplitude excitations . In a first part, we show how nonlinearity can affect the equipartiti on of energy in a lattice, and introduce some properties of nonlinear excitations and solitons. A second part investigates more precisely th e question of self-localization of the energy and the third part prese nt a simple theory of DNA thermal denaturation. We show in particular how the addition of a specific type of nonlinear coupling can cause a sharp ''melting'' transition in this one-dimensional system.