November 07: Riccardo Penco (Penn)

Time: 2pm
Location: 2N36
 
Title: Reinventing the wheel: an effective theory approach to dissipative spinning objects.
 
 Abstract: In this talk, I will show how effective field theory techniques can be used to shed a new light on the dissipative dynamics of spinning astrophysical objects. After introducing the basic formalism, I will discuss two different applications. The first one is a modern description of superradiance — a phenomenon by which a spinning object can loose angular momentum by amplifying the intensity of scattered radiation, or by producing particles in a bound state. Along the way, I will also provide a simple derivation of vacuum friction — a “quantum torque” that acts on spinning objects in empty space. The second application I will discuss (if time will allow it) is to tides and the role they play in the dynamics of moons, planets and other “Newtonian” objects. I will argue in particular that the time scales over which orbit circularization and tidal locking take place satisfy a hierarchy which follows exclusively from symmetry and is thus a model independent prediction of the effective theory.