FOURTH SYMPOSIUM ON COMPOSITIONAL STRUCTURES (SYCO 4) Chapman University, California, USA 22-23 May, 2019 http://events.cs.bham.ac.uk/syco/4/ The Symposium on Compositional Structures (SYCO) is an interdisciplinary series of meetings aiming to support the growing community of researchers interested in the phenomenon of compositionality, from both applied and abstract perspectives, and in particular where category theory serves as a unifying common language. The first SYCO was in September 2018, at the University of Birmingham. The second SYCO was in December 2018, at the University of Strathclyde. The third SYCO was in March 2019, at the University of Oxford. Each meeting attracted about 70 participants. The fourth SYCO will be in Chapman University, California, and we have 15 papers accepted for presentation, ranging over theory and practice of category theory, from homotopy type theory to differential programming, to rewriting systems, and to machine learning. Indeed the SYCO series aims to bring together the communities behind many previous successful events which have taken place over the last decade, including "Categories, Logic and Physics", "Categories, Logic and Physics (Scotland)", "Higher-Dimensional Rewriting and Applications", "String Diagrams in Computation, Logic and Physics", "Applied Category Theory", "Simons Workshop on Compositionality", and the "Peripatetic Seminar in Sheaves and Logic". # INVITED SPEAKERS John Baez, University of California, Riverside Tobias Fritz, Perimeter Institute for Theoretical Physics Nina Otter, University of California, Los Angeles # PAPERS ACCEPTED FOR PRESENTATION ??? Samuel Balco and Alexander Kurz, Nominal String Diagrams ??? Harsh Beohar and Sebastian K??pper, Bisimulation Maps in Presheaf Categories ??? Owen Biesel, Duality for Algebras of the Connected Planar Wiring Diagrams Operad ??? Daniel Cicala, Rewriting Structured Cospans ??? Cole Comfort, Circuit Relations for Real Stabilizers: Towards TOF+H ??? Kenny Courser and John Baez, Structured Cospans ??? Jonathan Gallagher, Benjamin MacAdam and Geoff Cruttwell, Towards Formalizing and Extending Differential Programming via Tangent Categories ??? Kohei Kishida, Soroush Rafiee Rad, Joshua Sack and Shengyang Zhong, Categorical Equivalence between Orthocomplemented Quantales and Complete Orthomodular Lattices ??? Benjamin MacAdam, Jonathan Gallagher and Rory Lucyshyn-Wright, Scalars in Tangent Categories ??? Jade Master, Generalized Petri Nets ??? Joe Moeller and Christina Vasilakopoulou, Monoidal Grothendieck Construction ??? Jeffrey Morton, 2-Group Actions and Double Categories ??? Michael Shulman, All (???,1)-Toposes Have Strict Univalent Universes ??? David Sprunger and Shin-Ya Katsumata, Differential Categories, Recurrent Neural networks, and Machine learning ??? Christian Williams and John Baez, Enriched Lawvere Theories for Operational Semantics # REGISTRATION Please register as soon as possible so that catering can be arranged. https://docs.google.com/forms/d/e/1FAIpQLScSmO-WYDjTOzRCW_NkY9Qrf1CebA3wteX9... # PROGRAMME COMMITTEE Miriam Backens, University of Oxford Ross Duncan, University of Strathclyde and Cambridge Quantum Computing Brendan Fong, Massachusetts Institute of Technology Tobias Fritz, Perimeter Institute for Theoretical Physics Stefano Gogioso, University of Oxford Amar Hadzihasanovic, Kyoto University Chris Heunen, University of Edinburgh Dominic Horsman, University of Grenoble Martti Karvonen, University of Edinburgh Kohei Kishida, Dalhousie University (chair) Andre Kornell, University of California, Davis Alexander Kurz, Chapman University Martha Lewis, University of Amsterdam Samuel Mimram, ??cole Polytechnique Benjamin Musto, University of Oxford Nina Otter, University of California, Los Angeles Simona Paoli, University of Leicester Dorette Pronk, Dalhousie University Mehrnoosh Sadrzadeh, Queen Mary Pawel Sobocinski, University of Southampton Joshua Tan, University of Oxford Sean Tull, University of Oxford Dominic Verdon, University of Bristol Jamie Vicary, University of Birmingham and University of Oxford Maaike Zwart, University of Oxford [For admin and other information see: http://www.mta.ca/~cat-dist/ ]