Theory of Heat pp 302-343 | Cite as

Fluctuations and Brownian Motion

  • Richard Becker


In thermodynamics the difference in entropy of two states I and II is given by
$${S_{II}} - {S_I} = {\left( {\int\limits_I^{II} {\frac{{\delta Q}}{T}} } \right)_{rev}}$$
where δQ is the heat supplied. The index “rev” means that the transition from I to II has to be carried out in a reversible way. If the quantum mechanical ground state E0 of the system is nondegenerate, the quantum theoretical phase volume Φ(E) approaches 1 for E just above E0, which means that the entropy, S & klnΦ, approaches zero. The entropy of the ground state can then be normalized to zero and one can define an absolute value of S by starting from the ground state E0 or from \(T = 0\left( {{S_1} = {S_{{E_o}}} = 0} \right)\):
$${S_{II}} = \int\limits_I^{II} {\frac{{\delta Q}}{T}} $$


Brownian Motion Diffusion Equation Spectral Distribution Shot Noise Cavity Radiation 
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Copyright information

© Springer-Verlag Berlin · Heidelberg 1955

Authors and Affiliations

  • Richard Becker
    • 1
  1. 1.Universität GöttingenGermany

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