Related Experiment Video
Updated: May 30, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Effective temperatures of a driven, strongly anisotropic Brownian system
1Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
Abstract:
We use Brownian dynamics computer simulations of a moderately dense colloidal system undergoing steady shear flow to investigate the uniqueness of the so-called effective temperature. We compare effective temperatures calculated from the fluctuation-dissipation ratios and from the linear response to a static, long-wavelength, external perturbation along two directions: the shear gradient direction and the vorticity direction. At high shear rates, when the system is strongly anisotropic, the fluctuation-dissipation-ratio-derived effective temperatures are approximately wave-vector independent, but the temperatures along the gradient direction are somewhat higher than those along the vorticity direction. The temperatures derived from the static linear response show the same dependence on the direction as those derived from the fluctuation-dissipation ratio. However, the former and the latter temperatures are different. Our results suggest that the presently used formulas for effective temperatures may not be applicable for strongly anisotropic, driven systems.
Related Concept Videos
Atomic Nuclei: Nuclear Spin State Population Distribution
Temperature and Thermal Equilibrium
The concept of temperature has evolved from the common concepts of hot and cold. The scientific definition of temperature explains more than just our sense of hot and cold. Temperature is operationally defined as the quantity measured with a thermometer. Furthermore, temperature is...
Atomic Spectroscopy: Effects of Temperature
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...
Mechanisms of Heat Transfer II
Effects of Temperature on Free Energy
Mechanisms of Heat Transfer I

