Journal of Noncommutative Geometry

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Volume 8, Issue 2, 2014, pp. 337–392
DOI: 10.4171/JNCG/159

Published online: 2014-07-18

Thermodynamic semirings

Matilde Marcolli[1] and Ryan Thorngren[2]

(1) California Institute of Technology, Pasadena, USA
(2) California Institute of Technology, Pasadena, USA

The Witt construction describes a functor from the category of Rings to the category of characteristic 0 rings. It is uniquely determined by a few associativity constraints which do not depend on the types of the variables considered, in other words, by integer polynomials. This universality allowed Alain Connes and Caterina Consani to devise an analogue of the Witt ring for characteristic one, an attractive endeavour since we know very little about the arithmetic in this exotic characteristic and its corresponding field with one element. Interestingly, they found that in characteristic one, the Witt construction depends critically on the Shannon entropy. In the current work, we examine this surprising occurrence, defining a Witt operad for an arbitrary information measure and a corresponding algebra we call a thermodynamic semiring. This object exhibits algebraically many of the familiar properties of information measures, and we examine in particular the Tsallis and Renyi entropy functions and applications to non-extensive thermodynamics and multifractals. We find that the arithmetic of the thermodynamic semiring is exactly that of a certain guessing game played using the given information measure.

Keywords: Entropy (Shannon, Renyi, Tsallis, Kullback–Leibler divergence), semiring, Witt construction, multifractals, operads, binary guessing games, entropy algebras

Marcolli Matilde, Thorngren Ryan: Thermodynamic semirings. J. Noncommut. Geom. 8 (2014), 337-392. doi: 10.4171/JNCG/159