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?

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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
>
> 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
--
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Prof Russell Standish Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics hpco...@hpcoders.com.au
University of New South Wales http://www.hpcoders.com.au
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