Time and Ontology in Quantum Field Theory

Title: From Causality to the Fundamental Structure of the World: Time and Ontology in Quantum Field Theory Research project: Is there an arrow of time directing how natural processes unfold at very small scales? And what are the microscopic constituents of our physical world? These are profound philosophical questions concerning time and ontology that have traversed the entire history of human thought. Yet, notwithstanding the formidable achievements of contemporary physics, especially in high-energy experiments, they still remain outstanding. The present project aims to answer such questions in the context of Quantum Field Theory that is our best physical model to account for the fundamental structure of the world. Specifically, it addresses open problems about time and ontology stemming from a condition of relativistic causality, also known as Einsteins principle of causality. Hypothesis: The question about the arrow of time will be answered by explaining how the temporal irreversibility we observe all around us can be recovered at the microscopic level, based on a result of Quantum Field Theory called CPT theorem. Then, the question about the fundamental constituents of matter will be answered by proposing an ontology in terms of quantum fields compatible with the emergence of particles in high-energy experiments, as well as by elaborating a refined notion of anti-matter. Methods: The proposed methodology has both a formal and a conceptual component. It consists in demonstrating relevant mathematical results within Quantum Field Theory and then interpreting their philosophical meaning, so as to clarify with precision the conceptual status and relations between the physical conditions at play. The direct interaction with international philosophers of physics and mathematical physicists sharing the same approach is also an important methodological aspect of the project. Scientific innovation: Given the growing attention of the scientific community, as well as of the general public, for the results of high-energy experiments, providing a solution of the problems at stake here is expected to have a great impact for our understanding of the fundamental structure of the world, thereby contributing to answer long-standing philosophical questions concerning time and ontology. Moreover, the proposed research will bring new approaches to the Philosophy Department at University of Salzburg, namely the host institution: in fact, while the latter hosts an active group of philosophers of physics, no work is currently done there on the foundations of Quantum Field Theory. In addition, the project aims to foster the creation of an international network in philosophy of physics that, beside Salzburg, will comprise even the groups operating at University of California at Irvine (US), the Munich Center for Mathematical Philosophy (Germany) and the Politecnico di Milano (Italy).

This project focused on the outstanding philosophical issues concerning time and ontology in physics. The research developed at University of Salzburg during the two years of funding dealt with the problem of what are the fundamental constituents of the microscopic world: since the latter are not directly observable, one can only make hypotheses about their nature, and in particular it is still controversial whether they are particles or fields. Furthermore, there is the question how to explain the irreversible behaviour observed at the macroscopic level notwithstanding the fact the dynamical laws governing the microscopic world are neutral with respect to the direction of time. A number of publications has been produced on the topic, both individually and in collaboration with the colleagues in the Department of Philosophy. In addition, the grant contributed to the creation and development of an international network including five schools, called the "Irvine-London-Munich-PoliMi-Salzburg Network in Philosophy and Foundations of Physics", which jointly organizes annual research events.