Fluctuations in an aging system: the absence of an effective temperature in the sol–gel transition of a quenched gelatin sample. (21st October 2015)

• Record Type: Journal Article
• Authors: Bérut, Antoine; Petrosyan, Artyom; Gomez-Solano, Juan Ruben; Ciliberto, Sergio
• Is Part Of: Journal of statistical mechanics. (2015:Oct.)
• Publication Date: 2015-10-21
• Subjects: 4 -- 7 -- 8; 4/210 -- 7/080 -- 7/130 -- 8/060; Statistical mechanics -- Periodicals; Mechanics -- Statistical methods -- Periodicals; 530.1305
• DOI: 10.1088/1742-5468/2015/10/P10020
• Languages: English
• ISSNs: 1742-5468

Abstract

Abstract: We study the fluctuations of a Brownian microparticle trapped using optical tweezers in a gelatin solution undergoing a fast local temperature quench below that required for the sol–gel transition. Contrary to what has previously been reported, we observe no anomalous fluctuations in the particle's position that could be interpreted in terms of an effective temperature. A careful analysis with ensemble averages shows only equilibrium-like properties for the fluctuations, even though the system is clearly aging. We also provide a detailed discussion on possible artifacts that could have been interpreted as an effective temperature, such as the presence of a drift, or a mixing between time average and ensemble average in the data analysis. These considerations are of general interest when dealing with nonergodic or nonstationary systems.