Uploaded August 2024 | Updated September 2026, 2 weeks ago
Topos Institute Colloquium, 8th of August 2024.
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Bayes' rule has recently been given a categorical definition in terms of string diagrams due to Cho and Jacobs. This definition of Bayesian inversion, however, is not robust enough for categories that include reasoning about quantum systems due to the no-cloning theorem. In this talk, I will explain how semi-cartesian categories (which have less structure than Markov categories) provide a suitable framework to define Bayesian inversion categorically. In particular, I will provide axioms for such an abstract form of Bayesian inversion. It remains an open question whether these axioms characterize Bayesian inversion for quantum systems.
Topos Institute Colloquium, 8th of August 2024.
———
Bayes' rule has recently been given a categorical definition in terms of string diagrams due to Cho and Jacobs. This definition of Bayesian inversion, however, is not robust enough for categories that include reasoning about quantum systems due to the no-cloning theorem. In this talk, I will explain how semi-cartesian categories (which have less structure than Markov categories) provide a suitable framework to define Bayesian inversion categorically. In particular, I will provide axioms for such an abstract form of Bayesian inversion. It remains an open question whether these axioms characterize Bayesian inversion for quantum systems.
![[2-torial] José tells Jason about coalgebraic-modal extensions of logic](https://i.ytimg.com/vi/UVj3BDy0iaU/mqdefault.jpg "[2-torial] José tells Jason about coalgebraic-modal extensions of logic
[2-torial] José tells Jason about coalgebraic-modal extensions of logic")
![[Oxford Seminar] Paolo Perrone | Descent in Probability Theory: the first steps downward](https://i.ytimg.com/vi/VG2RTE1R0BY/mqdefault.jpg "[Oxford Seminar] Paolo Perrone | Descent in Probability Theory: the first steps downward
Oxford Seminar, October 16 2025
Speaker: Paolo Perrone
Full Title: Descent in Probability Theory: the first steps downward
Abstract: Coarse-graining, forming quotients by dropping distinctions, is a unifying idea across mathematics: identifying the endpoints of an interval yields a circle; groups are conveniently presented as quotients of free ones; sheaves and stacks emerge from gluing local data. This idea is also central to probability, where “observing” a random variable similarly quotients a sample space via the sigma-algebra it generates (and is crucial for modeling randomness as ignorance). Yet this quotienting procedure, in probability, has so far lacked a systematic categorical treatment.
We develop a descent theory for probability that makes this intuition precise, while respecting probabilistic practice as much as possible. On the category theory side, the theory parallels classical descent, but diverges in a few ways due to the presence of stochastic dependence (correlations). On the probability side, it unifies the three core concepts of measurability, disintegration and stochastic dominance, within a single framework, providing conceptual understanding of the relationships between random variables, statistical experiments, and inference procedures.")
![[Oxford Seminar] B. Scot Rousse | Who cares about values?](https://i.ytimg.com/vi/VJZUZ37gj2Y/mqdefault.jpg "[Oxford Seminar] B. Scot Rousse | Who cares about values?
Oxford Seminar, 19th of June 2025
Today it is common to hear about “human values” and the importance of designing technologies that “align” with our values. But where does this notion of “human values” come from? In this talk I trace the history of the concept of human values. I connect this notion with an evolution in our understanding of human autonomy, and argue that both are inadequate abstractions for the challenges of being human in our technological age. Finally, I introduce the notion of care as an alternative to “values,” showing how it furnishes a subtler map for imagining and shaping our relationship to technology today.")
![[Berkeley Seminar] Brendan Fong | Processes of Production of Abstraction](https://i.ytimg.com/vi/WzAPGmW5YHQ/mqdefault.jpg "[Berkeley Seminar] Brendan Fong | Processes of Production of Abstraction
Title: Category Theory as the Formal Study of the Processes of Production of Abstraction
Abstract: For the last few months I’ve been reflecting on the phrase “Category theory is the formal study of the processes of production of abstraction”. I’ll say some words about what this phrase means to me. I ask your help inquiring about the epistemology of these meditations.
Date: 2025-06-10
https://topos.institute/events/berkeley-seminar/")
![[Oxford Seminar] David Jaz Myers | Compositionality via 2-algebra](https://i.ytimg.com/vi/XXIaJ98SUik/mqdefault.jpg "[Oxford Seminar] David Jaz Myers | Compositionality via 2-algebra
Oxford Seminar, May 28 2026
Speaker: David Jaz Myers
Full Title: Compositionality via 2-algebra
Abstract: A complex system may be designed modularly by putting together interacting component subsystems. Since analyses of complex systems can often scale very poorly with their size, it pays to use the modular structure of such systems to divide the task of analysis across the component subsystems.
Many analyses of systems may be encoded as homomorphism search problems between systems of the same sort. This suggests attending to categories of systems and their homomorphisms. In this talk, well consider the modular structure of a class of systems as a 2-algebra — an algebraic structure on categories of systems (and their interfaces and interaction patterns). Well see compositionality theorems as (lax) homomorphisms of these 2-algebraic structures, and survey a number of techniques for proving them using 2-categorical algebra.")
