Speaker
Dominik Wehr
University of Gothenburg
Talks at this conference:
Friday, 16:30, J330 
Unravelling cyclic arithmetic 
Cyclic proof systems admit derivations whose underlying structures are finite graphs rather than finite trees. Such proof systems are especially wellsuited to treating fixed points or (co)inductively defined concepts. A key problem of cyclic proof theory is proving the equivalence of cyclic and noncyclic proof systems for the same logic. The literature is the most developed for cyclic proof systems of Peano arithmetic, for which three distinct approaches to obtaining this equivalence are known: one based on the reverse mathematics of \(\omega\)automata theory [1,2], one based on infinite Ramsey theory [3] and one based on ‘unfolding’ proofs to exhibit certain structural properties [4]. In this talk, I will describe and compare all three approaches, illustrating the breadth of methods being brought to bear in cyclic proof theory. Bibliography
