Nonlinear localization in thermalized lattices: application to DNA

In the last few years numerous studies have been devoted to intrinsic local ized modes in nonlinear lattices because they provide examples of localizat ion without disorder. The properties of "discrete breathers" as exact solut ions of these nonlinear lattices are now well understood, but this is not t he case for the properties of nonlinear localization and energy relaxation in thermalized lattices. In biological molecules such as DNA, where large a mplitude nonlinear motions are essential for function, temporary deviations from energy equipartition could play an important role. After a brief intr oduction to intrinsic localized modes, we address the following questions: (a) does nonlinear localization survive in the presence of a thermal bath a nd how can we characterize it? (b) what is the origin of localization and h ow do discrete breathers contribute to it? (c) can we observe nonlinear loc alization in an experiment? The last point discusses recent results of an e xperiment performed on DNA, which suggest that the effects of nonlinear loc alization in a thermalized system may have already been observed. (C) 2000 Elsevier Science B.V. All rights reserved.