Information Symmetry

Conservation of information seems to be a deep physical principle. For instance, Unitarity is a key concept in Quantum Mechanics and Quantum Field Theory.

We may wonder if there is an underlying symmetry, in some space, which may explain this conservation of information.

quantum-mechanicsquantum-field-theoryquantum-informationnoethers-theoremunitarity Share Cite Improve this question Follow edited Oct 26, 2012 at 9:35 Qmechanic's user avatar Qmechanic♦ 198k4444 gold badges526526 silver badges22172217 bronze badges asked Oct 26, 2012 at 9:29 Trimok's user avatar Trimok 17.5k2626 silver badges6464 bronze badges Entropy. It's not a symmetry, but there's the second law of thermodynamics. – user14407

Oct 26, 2012 at 11:23

8 I am not talking about entropy, which is the unknown information about some system, for a particular observer. I talk about information. – Trimok

Oct 26, 2012 at 11:25 

2 @Trimok Are the known information and the loss thereof (entropy) about a system not related by something like "as the entropy increases the information decreases" ...? Could it be that you are right when one talks about a fine grained microscopic description of the system which is reversible and therefore both, information and entropy are conserved (such that it is very interesting to ask for a symmetry corresponding to the conservation of information +1), and Lunge is right when talking about course grained systems that dont conserve entropy and information when not in equilibrium ? – Dilaton

Oct 26, 2012 at 12:32

3 Well, I am maybe wrong, but I think that information is always conserved, but entropy always increases. And I think also, that this applies to microscopic systems as well as to macroscopic systems. But I concede that all these questions are very subtle, because you have to decide what is subjective, what is objective, what is the role of the observer, and so on.

References

• See the wiki page AI for Quantum Physics