Ensemble fluctuations matter for variances of macroscopic variables - Archive ouverte HAL
Article Dans Une Revue European Physical Journal E: Soft matter and biological physics Année : 2021

Ensemble fluctuations matter for variances of macroscopic variables

G George
  • Fonction : Auteur
L Klochko
J Baschnagel
J P Wittmer

Résumé

Extending recent work on stress fluctuations in complex fluids and amorphous solids we describe in general terms the ensemble average v(∆t) and the standard deviation δv(∆t) of the variance v[x] of time series x of a stochastic process x(t) measured over a finite sampling time ∆t. Assuming a stationary, Gaussian and ergodic process, δv is given by a functional δvG[h] of the autocorrelation function h(t). δv(∆t) is shown to become large and similar to v(∆t) if ∆t corresponds to a fast relaxation process. Albeit δv = δvG[h] does not hold in general for non-ergodic systems, the deviations for common systems with many microstates are merely finite-size corrections. Various issues are illustrated for shear-stress fluctuations in simple coarse-grained model systems.
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Dates et versions

hal-03010090 , version 1 (17-11-2020)

Identifiants

Citer

G George, L Klochko, A N Semenov, J Baschnagel, J P Wittmer. Ensemble fluctuations matter for variances of macroscopic variables. European Physical Journal E: Soft matter and biological physics, 2021, 44 (2), pp.13. ⟨10.1140/epje/s10189-020-00004-7⟩. ⟨hal-03010090⟩
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