Global dynamical friction in cored galaxies

Global dynamical theories have completely changed our understanding of stellar dynamics, by putting forth the importance of resonant interactions. These phenomena are applicable to a broad range of astrophysical scales from planetary systems and star clusters to galaxies and even galaxy clusters. I will discuss the novel global approach to dynamical friction in the context of low-mass galaxies. Classical dynamical friction theory relying on local interactions, overpredicts the strength of frictional torques in the background cored distribution of mass. Global interactions take into account real orbital structure and rely on resonant encounters between the perturer and background "stars". In the innermost regions of the core, the global dynamical friction becomes highly suppressed that the further infall of perturber's orbit is effectively stalled. I will discuss this phenomenon of core stalling and its relevance for the low-mass galaxies, both dwarfs and ultra diffuse galaxies, abundant in old globular clusters. These systems are a perfect testing ground of these dynamical theories, that can help probe the underlying mass distribution of the host dark matter halo and the nature of dark matter itself. (Apart from the global stellar dynamics, I will briefly present my recent work on radiation pressure instability of magnetic accretion disks in the context of a new class of X-ray transients called quasi-periodic eruptions and also, tidal disruption events.)