# Tsallis entropy and other generalizations

If I am given a system, which I might have to describe using a generalized entropy, like the "q-deformed" Tsallis entropy, do I have to fit q from experiment or might I know it beforehand? How do I know the parameter q and/or how can I possibly obtain the degree of non-extensitivity via experiment? How can I measure the entropy of a part of the system, if the system is non-extensive?

http://en.wikipedia.org/wiki/Tsallis_entropy

Edit:

After some browsing I think the answer might be related to the fact, that for q-deformed entropy, the most probable distribution is not the Gaussian, but seems to be the q-deformed Gaussian:

http://en.wikipedia.org/wiki/Q-Gaussian

Then I played around a bit:

http://img835.imageshack.us/img835/5841/qgaussian.png

Maybe one applies such an entropy concept if one comes across a distribution of such type, but that's only a guess. And I don't see why one would/could conclude non-extensitivity from a distribution?!

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Can you give one example? I am struggling to find a single case which is described by this thing. –  Ron Maimon Oct 10 '11 at 6:04