1-5 July 2019
The University of Manchester
Europe/London timezone
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Dynamical friction in a superfluid

Presented by Dr. Benjamin ELDER on 2 Jul 2019 from 17:40 to 18:00
Type: oral presentation
Track: Cosmological Probes


Several modern theories hypothesize that dark matter condenses to a superfluid phase around galaxies. If true, one key distinction from particle dark matter is dynamical friction, a process by which a massive perturber moving through a cloud of matter is slowed by the gravitational attraction to its own wake. I will describe the steady-state dynamical friction of a perturber moving through a superfluid condensate. Crucially, I will account for the tachyonic gravitational mass of sound waves (a consequence of the Jeans instability of the fluid cloud), as well as the “quantum pressure” of the gas. I will show this in two equivalent ways: (i) via a familiar approach in which one linearizes the fluid equations, and (ii) via a novel quasiparticle description of phonon radiation. Although subsonic perturbers are ordinarily unable to experience a drag force in a superfluid, surprisingly we will find that the Jeans instability modifies the dispersion relation enough to result in small, but non-vanishing, subsonic dynamical friction. This effect may be a key observable in distinguishing between particle and fluid models of dark matter.


Location: Schuster
Room: Rutherford Lecture Theatre

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