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The definitions in the second link are worth thinking about: http://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory http://en.wikipedia.
by jpdoctor 14y ago
The definitions in the second link are worth thinking about: http://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory http://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_i...
There is no requirement that information has a physical representation for information-theoretic entropy. Landauer's result assumes that it does have a physical representation, and derives some physical consequences.
- wyuenho 14y agoHow to you carry information without a physical medium?
- dchichkov 14y agoI think his argument, is that I have no right to talk about bits [edit: in the context of stat mech], before defining physical representation of these bits - that is a physical system, states and transitions between states.
- jpdoctor 14y ago> is that I have no right to talk about bits, before defining physical representation of these bits I'm saying something slightly different: You can talk about bits in a system without a physical representation; That system can have an information-entropy associated with it. Once you implement a physical system representing those bits, then Landauer's comment applies.
- dchichkov 14y agoYes. You are right of course. There is no requirement that information necessarily has a physical representation. But, if I'm not wrong, this requirement could always be satisfied, for any system with two or more microstates.
- jpdoctor 14y agoA simple example where information-theoretic entropy is used where there is no physical representation: Video codecs. I'm guessing you've heard of mpeg and h.264 encoding. Which one encodes a movie better? One way of answering this question is to ask: Which codec added less entropy (perhaps for the same compression)? For that matter: Before Shannon's information entropy, one might wonder if there is a way (another codec) perhaps recovering the information after mpeg coding and decoding. However, now you know that information-entropy can only increase or stay the same, which tells you that subsequent "correction codec" cannot remove entropy introduced by mpeg codec.
- dchichkov 14y agoThanks. I don't really like that example with codecs, because I could always argue that any codec can only be a physical system, operating in some environment at temperature T and will be constrained by Landauer's, ets. Either way, I think we've digressed. I'm actually very happy with yours: "Adding energy to a system with negative temperature reduces the number of microstates.", because this is clear and unambiguous.