## 2020-2021

**Upcoming talks:**

5 June 2021, 3pm, Via Zoom (link shared by email)

**Adam Koberinski (Waterloo / Bonn), “Lambda and the limits of effective field theory”****Abstract:** The cosmological constant problem stems from treating a semiclassical merger of quantum field theory and general relativity as an effective field theory. We argue that the problem is best understood as a *reductio ad absurdum*, and that one should reject the assumption that general relativity can generically be treated as an effective field theory. In this paper we make explicit the sensitive dependence of the cosmological constant Lambda on high-energy physics, and outline the assumptions behind naturalness and the effective field theory framework. We show that these assumptions are violated in general relativistic domains where Lambda is relevant, so one should not expect effective field theory methods to apply. We argue that the failure of naturalness signalled by the cosmological constant problem is not a deep problem for the future of physics, and highlight some current “unnatural” solutions to the problem.

———–Previous Talks———–

1 May 2021, 3pm, Via Zoom (link shared by email)

**Christopher Gregory Weaver (Illinois, Urbana-Champaign), “Hamilton, Hamiltonian Mechanics, and Causation”****Abstract**: I show how Hamilton’s philosophical commitments led him to a causal interpretation of classical mechanics. I argue that Hamilton’s metaphysics of causation was injected into his dynamics by way of a causal interpretation of force. I then detail how forces remain indispensable to both Hamilton’s formulation of classical mechanics and what we now call Hamiltonian mechanics (*i.e*., the modern formulation). On this point, my efforts primarily consist of showing that the orthodox interpretation of potential energy is the interpretation found in Hamilton’s work. Hamilton called the potential energy function the force-function because he believed that it represents forces at work in the world. Multifarious non-historical arguments for this orthodox interpretation of potential energy are provided, and matters are concluded by showing that in classical Hamiltonian mechanics, facts about the potential energies of systems are grounded in facts about forces. Thus, if one can tolerate the view that forces are causes of motions, then Hamilton provides one with a road map for transporting causation into one of the most mathematically sophisticated formulations of classical mechanics, *viz*., Hamiltonian mechanics.