title: Fluctuation-response relation in turbulent systems.
abstract: We address the problem of measuring time properties of response functions (Green functions) in Gaussian models (Orszag-McLaughin) and strongly non-Gaussian models (shell models for turbulence). We introduce the concept of halving-time statistics to have a statistically stable tool to quantify the time decay of response functions and generalized response functions of high order. We show numerically that in shell models for three-dimensional turbulence response functions are inertial range quantities. This is a strong indication that the invariant measure describing the shell-velocity fluctuations is characterized by short range interactions between neighboring shells.
authors.affiliation: Department of Physics and INFM, University of Rome "Tor Vergata," Via della Ricerca Scientifica 1, I-00133 Roma, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Biferale
authors.forename: I
authors.initials: I
authors.lastname: Daumont
authors.forename: G
authors.initials: G
authors.lastname: Lacorata
authors.forename: A
authors.initials: A
authors.lastname: Vulpiani