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Physics & Astronomy/STAR cluster seminar: The effective fluid formalism in scalar-tensor gravity
January 24 @ 2:30 pm
By Jeremy Côté
Scalar-tensor gravity is a framework in which one generalizes general relativity, modifying the behaviour of gravity on various scales. Two such popular frameworks are Brans-Dicke gravity and f (R) gravity. When looking at the field equations for these theories, they are similar to those of general relativity, with extra terms appended (due to an extra scalar field). These extra terms can be regarded as an “effective” stress-energy tensor that describes an imperfect fluid. In this presentation, I will introduce the basics of scalar-tensor gravity (the field equations, the metric and projection tensors, the stress-energy tensor for an imperfect fluid), explain the effective fluid formalism of scalar-tensor gravity, go over its dynamics, the conformal symmetries of the scalar-tensor action, and then show how this formalism can make evident an anomaly when trying to reach general relativity as a “limit” of Brans-Dicke gravity.