Re: [Phys-l] the uniqueness of entropy

[William Maddox <maddox@physics.auburn.edu>]

From: WC Maddox

    Not everyone agrees with 2a even within physics. The authors of the 
paper on entropy in the July issue of AJP, who are disagree with 
Swendsen's Journal of Statistical Physics article, state: " The key to 
the resolution is the recognition that the entropy concept in 
thermodynamics is not identical to that in statistical mechanics".
    They also state:that   "According to both statistical mechanics and 
thermodynamics, the second law is obeyed perfectly. The statistical 
mechanical account is that the number of microstates increases through 
intervention from outside the removal of the partition, and
the statistical second law tells us that the system will subsequently 
make maximum use of the increased area in phase
space. Therefore, the prediction is that the system will exhibit 
equilibrium values of its macroscopic quantities, so that
on the macrolevel nothing changes. In thermodynamics this "fine-grained" 
consideration plays no role: nothing changes,
and according to the thermodynamic second law, the entropy remains 
constant."
    They state further " The same type of argument can be used if we 
consider what happens when the partition is replaced. *According to
thermodynamics, nothing happens to the entropy because there is no 
exchange of heat.* *According to statistical physics,*
*there is a decrease of W and thus of the entropy. But this decrease 
does not mean a violation of the second law!* The
decrease in W is a consequence of the redefinition of the accessible 
phase space caused by intervention in the system.
The statistical second law remains valid and predicts that the two 
subsystems will fully make use of their phase space
possibilities which in this case means that equilibrium will be 
maintained."

Here at least a PDF copy can be obtained from: 
http://ajp.aapt.org/resource/1/ajpias/v79/i7/p741_s1. This may not be 
available where you work.

End Message

On 6/29/2011 11:53 AM, John Denker wrote:
> *2a) In science, there is only one definition of entrop*y.
>
> 2b) Outside of science, there are many nontechnical and metaphorical
>   definitions of "entropy", but this does not change fact (2a).
>
>
> rum for Physics Educators
> Phys-l@carnot.physics.buffalo.edu
> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l