, Volume 148, Issue 1, pp 1-37,
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Long Time, Large Scale Limit of the Wigner Transform for a System of Linear Oscillators in One Dimension

Abstract

We consider the long time, large scale behavior of the Wigner transform W ϵ (t,x,k) of the wave function corresponding to a discrete wave equation on a 1-d integer lattice, with a weak multiplicative noise. This model has been introduced in Basile et al. in Phys. Rev. Lett. 96 (2006) to describe a system of interacting linear oscillators with a weak noise that conserves locally the kinetic energy and the momentum. The kinetic limit for the Wigner transform has been shown in Basile et al. in Arch. Rat. Mech. 195(1):171–203 (2009). In the present paper we prove that in the unpinned case there exists γ 0>0 such that for any γ∈(0,γ 0] the weak limit of W ϵ (t/ϵ 3/2γ ,x/ϵ γ ,k), as ϵ≪1, satisfies a one dimensional fractional heat equation $\partial_{t} W(t,x)=-\hat{c}(-\partial_{x}^{2})^{3/4}W(t,x)$ with $\hat{c}>0$ . In the pinned case an analogous result can be claimed for W ϵ (t/ϵ 2γ ,x/ϵ γ ,k) but the limit satisfies then the usual heat equation.