Asymptotic analysis of combined breather-kink modes in a Fermi-Pasta-Ulam chain

Butt, Imran A and Wattis, Jonathan AD (2007) Asymptotic analysis of combined breather-kink modes in a Fermi-Pasta-Ulam chain. Physica D, 231 . pp. 165-179.

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We find approximations to travelling breather solutions of the one-dimensional Fermi-Pasta-Ulam (FPU) lattice. Both bright breather and dark breather solutions are found. We find that the existence of localised (bright) solutions depends upon the coefficients of cubic and quartic terms of the potential energy, generalising an earlier inequality derived by James [CR Acad Sci Paris 332, 581, (2001)]. We use the method of multiple scales to reduce the equations of motion for the lattice to a nonlinear Schr{\"o}dinger equation at leading order and hence construct an asymptotic form for the breather. We show that in the absence of a cubic potential energy term, the lattice supports combined breathing-kink waveforms. The amplitude of breathing-kinks can be arbitrarily small, as opposed to traditional monotone kinks, which have a nonzero minimum amplitude in such systems. We also present numerical simulations of the lattice, verifying the shape and velocity of the travelling waveforms, and confirming the long-lived nature of all such modes.

Item Type:Article
Uncontrolled Keywords:breathers, non-linear waves, discrete systems
Schools/Departments:Faculty of Science > School of Mathematical Sciences
ID Code:925
Deposited By:Wattis, Jonathan
Deposited On:23 Jul 2008 15:30
Last Modified:24 Jun 2011 15:34

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