SOME NOTES ON EINSTEIN RELATIONSHIPS

Transport coefficients are often expressed in the form of an Einstein relationship. In this report we point out some possibly surprising pro perties of the correlation functions appearing in such expressions and we discuss under what conditions the relationships are true. We furth er consider the Einstein relationship for the shear viscosity proposed by McQuarrie [in Statistical Mechanics (Harper and Row), 1976]. On th e basis both of theoretical analysis and computer simulation, we concl ude that this expression is incorrect.