BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Linear stability of disk galaxies - Dr. Sven De Rijcke - Ghent Uni versity DTSTART:20211011T130000Z DTEND:20211011T140000Z UID:TALK158461@talks.cam.ac.uk CONTACT:Dr Can Cui DESCRIPTION:An attractive theory for the occurrence of spiral patterns in simulated and\, hopefully\, real disc galaxies is based on the idea that t he underlying stellar disc is linearly unstable and spontaneously grows ei genmodes. These rotating\, overlapping modes then form the changing\, tran sient patterns that are observed in simulated discs (Sellwood & Carlberg 2 014). This obviously begs the question why these discs are linearly unstab le to begin with. Using the linearized Boltzmann equation\, I investigate how grooves carved in the phase space of a stellar disc can trigger the vi gorous growth of two-armed spiral eigenmodes (De Rijcke\, Fouvry\, Pichon 2019). Such grooves result from the self-induced dynamics of a disc subjec t to finite-N shot noise\, as swing-amplified noise patterns push stars to wards lower angular momentum orbits at their inner Lindblad radius (Sellwo od 2012\, Fouvry et al. 2015). I provide evidence that the depletion of ne ar-circular orbits\, and not the addition of radial orbits\, is the crucia l physical ingredient that causes these new eigenmodes. Thus\, it is possi ble for an isolated\, linearly stable stellar disc to spontaneously become linearly unstable via the self-induced formation of phase-space grooves t hrough finite-N dynamics. In order to be able to compare the linear stabil ity computations directly with N-body simulations\, they were equipped wit h gravitational softening (De Rijcke\, Fouvry\, Dehnen 2019). I also show some first results obtained using this linear stability code with the incl usion of the gravitational coupling between a stellar disc and a cooling g as disc\, which enables the search for eigenmodes in the star+gas system. LOCATION:Online END:VEVENT END:VCALENDAR