Title: Emergence and Naturalness

David Wallace
Mellon Chair in Philosophy and History & Philosophy of Science
University of Pittsburgh

If we want to start with the physics of the very small - molecules, atoms, subatomic particles - and work out the physics of large-scale systems - dust grains, iron bars, planets – we need to assume more than the laws of the very small: we have to make an additional assumption, often called “naturalness.” Despite the name, this assumption is puzzling in many respects, and the puzzle deepens into paradox because in our best theories of fundamental physics it seems to fail in two very specific places – the mass of the Higgs boson, and the rate of expansion of the Universe. In the lecture, I’ll explain what the naturalness assumption is, why we need it in almost all of physics, and why its failure in particle physics and cosmology is one of the deepest problems in contemporary physics.