Europhys. Lett.
Volume 76, Number 6, December 2006
Page(s) 1022 - 1028
Section General
Published online 16 November 2006
Europhys. Lett., 76 (6), pp. 1022-1028 (2006)
DOI: 10.1209/epl/i2006-10386-y

Violation of the fluctuation-dissipation theorem in confined driven colloids

R. Mauri1 and D. Leporini2, 3

1  Dipartimento di Ingegneria Chimica, DICCISM, Università di Pisa I-56126 Pisa, Italy
2  Dipartimento di Fisica "Enrico Fermi", Università di Pisa Largo B. Pontecorvo 3, I-56127 Pisa, Italy
3  SOFT-INFM-CNR - P.zza A. Moro 2, I-00185, Roma, Italy

received 27 July 2006; accepted in final form 20 October 2006
published online 16 November 2006

Analytical models describing a colloidal particle confined in a harmonic well, e.g. provided by an optical trap, and driven by shear flows are presented. Violation of both static and dynamic fluctuation-dissipation theorem (FDT) is clearly seen, thus clarifying the connection between such FDT violation and the breakdown of the detailed balance. The simple shear and Taylor-Couette velocity fields are studied in detail, showing that loosening confinement enhances FDT violations. In addition, cases violating FDT but not energy equipartition are presented. For the cases under study, an effective temperature is defined via the static FDT, which appears to be more physically sound than the one defined via the time-dependent FDT. Confining sheared colloidal particles by optical tweezers yields considerable FDT violation.

05.40.-a - Fluctuation phenomena, random processes, noise, and Brownian motion.

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