Superballistic and superdiffusive scaling limits of stochastic harmonic chains with long-range interactions

We consider one-dimensional infinite chains of harmonic oscillators with random exchanges of momenta and long-range interaction potentials which have polynomial decay rate vertical bar x vertical bar(-theta) , x -> infinity, theta > 1 where x is an element of Z is the interaction range. The dynamics conserve total momentum, total length and total energy. We prove that the systems evolve macroscopically on superballistic space-time scale (y epsilon(-1),t epsilon(-theta-1/2)) when 1 < theta < 3, (y epsilon(-1),t epsilon(-1)root log(epsilon(-1))(-1)) when theta = 3, and hyperbolic space-time scale (y epsilon(-1), t epsilon(-1)) when theta > 3. Combining our results and the results in (Suda 2021 Ann. Inst. Henri Poincare B 57 2268-2314), we show the existence of two different space-time scales on which the systems evolve. In addition, we prove the fluctuations of the normal modes of the superballistic wave equation, which are analogues of the Riemann invariants and capture fluctuations along the characteristics. For the normal modes, the space-time scale is superdiffusive when 2 < theta <= 4 and diffusive when theta > 4.