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Categorical Information Geometry

Part of the Lecture Notes in Computer Science book series (LNCS,volume 14071)


Information geometry is the study of interactions between random variables by means of metric, divergences, and their geometry. Categorical probability has a similar aim, but uses algebraic structures, primarily monoidal categories, for that purpose. As recent work shows, we can unify the two approaches by means of enriched category theory into a single formalism, and recover important information-theoretic quantities and results, such as entropy and data processing inequalities.


  • Category Theory
  • Markov Categories
  • Graphical Models
  • Divergences
  • Information Geometry

Supported by Sam Staton’s ERC grant “BLaSt – A Better Language for Statistics”.

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  1. 1.

    Despite the name, Markov categories are not only suited to model Markov processes, but arbitrary stochastic processes. Indeed, arbitrary joint distributions can be formed, and the Markov property states that the stochastic dependencies between the variables are faithfully represented by a particular graph. If the graph is (equivalent to) a single chain, we have a Markov process. In general, the graph is more complex. In this respect, Markov categories are similar to, but more general than, Markov random fields. See [6] for more details on this.

  2. 2.

    The geometry of the category of Markov kernels studied by Chentsov in [2, Sects. 4 and 6] is not metric geometry, it is a study of invariants in the sense of Klein’s Erlangen Program. More related to the present work are, rather, the invariant information characteristics of Sect. 8 of [2]. Much of classical information geometry, and hence indirectly this work, is built upon those notions.


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The author would like to thank Tobias Fritz, Tomáš Gonda and Sam Staton for the helpful discussions and feedback, the anonymous reviewers for their constructive comments, and Swaraj Dash for the help with translating from Russian.

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Perrone, P. (2023). Categorical Information Geometry. In: Nielsen, F., Barbaresco, F. (eds) Geometric Science of Information. GSI 2023. Lecture Notes in Computer Science, vol 14071. Springer, Cham.

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