Dynamical Friction in Interacting Relativistic Systems. (arXiv:1906.05341v1 [hep-ph])

<a href="http://arxiv.org/find/hep-ph/1/au:+Katz_A/0/1/0/all/0/1">Andrey Katz</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Kurkela_A/0/1/0/all/0/1">Aleksi Kurkela</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Soloviev_A/0/1/0/all/0/1">Alexander Soloviev</a>

We study dynamical friction in interacting relativistic systems with

arbitrary mean free paths and medium constituent masses. Our novel framework

recovers the known limits of ideal gas and ideal fluid when the mean free path

goes to infinity or zero, respectively, and allows for a smooth interpolation

between these limits. We find that in an infinite system the drag force can be

expressed as a sum of ideal-gas-like and ideal-fluid-like contributions leading

to a finite friction even at subsonic velocities. This simple picture receives

corrections in any finite system and the corrections become especially

significant for a projectile moving at a velocity $v$ close to the speed of

sound $vapprox c_s$. These corrections smoothen the ideal fluid discontinuity

around the speed of sound and render the drag force a continuous function of

velocity. We show that these corrections can be computed to a good

approximation within effective theory of viscous fluid dynamics.

We study dynamical friction in interacting relativistic systems with

arbitrary mean free paths and medium constituent masses. Our novel framework

recovers the known limits of ideal gas and ideal fluid when the mean free path

goes to infinity or zero, respectively, and allows for a smooth interpolation

between these limits. We find that in an infinite system the drag force can be

expressed as a sum of ideal-gas-like and ideal-fluid-like contributions leading

to a finite friction even at subsonic velocities. This simple picture receives

corrections in any finite system and the corrections become especially

significant for a projectile moving at a velocity $v$ close to the speed of

sound $vapprox c_s$. These corrections smoothen the ideal fluid discontinuity

around the speed of sound and render the drag force a continuous function of

velocity. We show that these corrections can be computed to a good

approximation within effective theory of viscous fluid dynamics.

http://arxiv.org/icons/sfx.gif