# Abstract Cyclic Proofs

## Dominik Wehr, FLoV

Cyclic proof systems permit derivations to contain cycles, thereby serving as finite representations of non-wellfounded derivation trees. Such cyclic proof systems have been proposed for a broad range of logics, especially those with fixed-point features or inductively defined objects of reasoning. The soundness of such systems is commonly ensured by only considering those cyclic derivations as proofs which satisfy a so-called global trace condition.

In this talk, I will present a category theoretical notion, the trace category, which generalizes the trace condition of many cyclic proof systems. Indeed, a handful of different trace categories are sufficient to capture the trace conditions of all cyclic proof systems from the literature I have examined so far. The arising abstract notion of cyclic proof allows for the derivation of generalized renditions of standard results of cyclic proof theory, such as the decidability of proof-checking and the regularizability of certain non-wellfounded proofs. It also opens the door to broader inquiries into the structural properties of trace condition based cyclic and non-wellfounded proof systems, some of which I will touch on in this talk, time permitting. The majority of this talk will be based on my Master’s thesis.