[Fis] Replies and new questions / part 1

To: <fis@listas.unizar.es>
Subj: Replies and new questions / part 1

Dear FISers,

Following Michael Devereux, I merge several replies in a single
email. I beg my pardon from Pedro bacause this is just a tool
to being not parsimonious without sending too many emails per week.
Nevertheless, I promise that the lengths of my emails remain short.
So, FISers can read more easily emails when they are short:
parsimony is rediscovered here.

About the Szilard-Brillouin relation mentioned by Loet Leydesdorff
(thank you, Loet, for the pointer):
I have not looked to the derivation of the relation. When the
thermodynamical information is introduced via the Shannon formula,
applied to a probabilistic model involved in the entropy calculation
(as it occurs frequently in statistical mechanics), I would say
that it is an <<information theory>> concept of the information
in thermodynamics, rather than a strictly <<thermodynamic>> concept
of information.

About the relations entropy/order-disorder/symmetry, mentioned by Shu-Kun Lin:
I had in the past several discussions with Shu-Kun about this topic.
It appeared that order/disorder is a paradoxical concept, which is
not very clear. Here is an simple example, based upon samples of the
uniform law in a square. N being the size of a sample, my question is:
does order decreases and disorder increases when N increases, or
does order increases and disorder decreases when N increases ?
I shall give my own view in a future email.
The same question for entropy or information may be easier to answer,
because we are in a strictly probabilistic context.

About the thermodynamic equilibrium and the universe, in the reply of Stan Salthe:
Since cosmology is far from my field, I confess to have difficulties to
understand the properties of the system <<our universe>>, viewed from the
thermodynamical viewpoint. Even the cooling of such an expanding system
is not clear for me, since, despite that the expansion is (locally) currently
observed, I do not know what will happen after some 1O^10 years or more
(does anybody knows ?), and may be there are cycles, may be there are
aperiodic contractions, may be there is...anything. I would like to
hear further opinions about this.

About the number of microstates, evoked in the email of Igor Rojdestvenski:
Just a question here, for anybody in the list: usual models of thermodynamical
systems assume countable number of microstates. Is this an acceptable
assumption ?

Michel Petitjean Email: petitjean@itodys.jussieu.fr
Editor-in-Chief of Entropy entropy@mdpi.org
ITODYS (CNRS, UMR 7086) ptitjean@ccr.jussieu.fr
1 rue Guy de la Brosse Phone: +33 (0)1 44 27 48 57
75005 Paris, France. FAX : +33 (0)1 44 27 68 14
http://www.mdpi.net http://www.mdpi.org
http://petitjeanmichel.free.fr/itoweb.petitjean.html
http://petitjeanmichel.free.fr/itoweb.petitjean.freeware.html
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Received on Thu Apr 8 13:23:03 2004