Date(s) - 12/05/2014
5:15 pm - 6:45 pm
Lakatos (LAK) 2.06
Speaker: J. Brian Pitts (Cambridge)
Time: 5:15pm – 6:45pm
Title: Real Change Happens in Hamiltonian General Relativity
Abstract: In General Relativity in Hamiltonian form, change has seemed to be missing, because the Hamiltonian is a sum of first-class constraints and thus supposedly generates gauge transformations. The gauge generator, a specially _tuned sum_ of first-class constraints, facilitates seeing that a solitary first-class constraint generates not a gauge transformation, but a bad physical change in electromagnetism or General Relativity, spoiling the constraints, Gauss’s law or the Gauss-Codazzi relations, in terms of the physically relevant velocities. Insistence on Hamiltonian-Lagrangian equivalence holds the key, including a reformed Bergmann-inspired notion of observables. Taking objective change to be ineliminable time dependence, there is change in GR without matter just in case there is no time-like Killing vector. The Hamiltonian formalism agrees.