Fluctuation-dissipation theorem for frequency-dependent specific heat
Abstract
A derivation of the fluctuation-dissipation (FD) theorem for the frequency-dependent specific heat of a system described by a master equation is presented. The FD theorem is illustrated by a number of simple examples, including a system described by a linear Langevin equation, a two-level system, and a system described by the energy master equation. It is shown that for two quite different models with low-energy cutoffs-a collection of two-level systems and a system described by the energy master equation-the frequency-dependent specific heat in dimensionless units becomes universal at low temperatures, i.e., independent of both energy distribution and temperature. These two models give almost the same universal frequency-dependent specific heat, which compares favorably to experiments on supercooled alcohols.
- Publication:
-
Physical Review B
- Pub Date:
- December 1996
- DOI:
- 10.1103/PhysRevB.54.15754
- Bibcode:
- 1996PhRvB..5415754N
- Keywords:
-
- 64.70.Pf;
- 65.20.+w;
- 05.40.+j;
- Glass transitions;
- Thermal properties of liquids: heat capacity thermal expansion etc.