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Wednesday, March 11, 2009
10:00 AM - 11:00 AM
CNLS Conference Room (TA-3, Bldg 1690)


What is the Temperature of a Deforming Glass

James Langer
University of California at Santa Barbara

The state of configurational disorder of an amorphous material is naturally characterized by an effective temperature Teff, which is generally different from the ordinary temperature when the material is near or below the glass transition and is being driven out of mechanical equilibrium. My main illustration of the role of Teff will be an analysis of extensive MD simulations by Haxton and Liu, in which Teff is measured directly and is seen to play an unexpectedly important, "quasi-thermodynamic" role. In particular, it appears that there exists a glass transition as a function of Teff at thermal temperatures below the equilibrium glass transition. If time permits, I will talk about recent efforts to develop a systematic theory of the effective temperature. These efforts have required a reexamination of the relation between the classic thermodynamic and statistical statements of the second law of thermodynamics.

Host: Bob Ecke, T-CNLS