On 02.02.2012 22:35 Russell Standish said the following:
On Wed, Feb 01, 2012 at 09:17:41PM +0100, Evgenii Rudnyi wrote:
On 29.01.2012 23:06 Russell Standish said the following:


Absolutely! But at zero kelvin, the information storage capacity
of the device is precisely zero, so cooling only works to a
certain point.


I believe that you have mentioned once that information is
negentropy. If yes, could you please comment on that? What
negentropy would mean?

Scheodinger first pointed out that living systems must export
entropy, and coined the term "negative entropy" to refer to this.
Brillouin shortened this to negentropy.

The basic formula is S_max = S + I.

S_max is the maximum possible value for entropy to take - the value
of entropy at thermodynamic equilibrium for a microcanonical
ensemble. S is the usual entropy, which for non-equilibrium systems
will be typically lower than S_max, and even for equilibrium systems
can be held lower by physical constraints. I is the difference, and
this is what Brillouin called negentropy. It is an information - the
information encoded in that state.

Try looking up http://en.wikipedia.org/wiki/Negentropy

Could you please explain how the negentropy is related to experimental thermodynamics? You will find in the previous message the link to the JANAF tables and a basic thermodynamic problem. Could you please demonstrate how the negentropy will help there?



In general, I do not understand what does it mean that information
at zero Kelvin is zero. Let us take a coin and cool it down. Do
you mean that the text on the coin will disappear? Or you mean that
no one device can read this text at zero Kelvin?


I vaguely remembered that S_max=0 at absolute zero. If it were, then
both S and I must be zero, because these are all nonnegative
quantities. But http://en.wikipedia.org/wiki/Absolute_zero states
only that entropy is at a minimum, not stricly zero. In which case,
I withdraw that comment.

Cheers

First, we have not to forget the Third Law that states that the change in entropy in any reaction, as well its derivatives, goes to zero as the temperatures goes to zero Kelvin.

In this respect your question is actually nice, as now, I believe, we see that it is possible to have a case when the information capacity will be more than the number of physical states.

Evgenii

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