The Resonant Gravitational instability from Baryon-Dark Matter relative Streaming

          @misc{ scivideos_PIRSA:26040114,
            doi = {10.48660/26040114},
            url = {https://pirsa.org/26040114},
            author = {Shalaby, Mohamad},
            keywords = {Cosmology},
            language = {en},
            title = {The Resonant Gravitational instability from Baryon-Dark Matter relative Streaming},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2026},
            month = {apr},
            note = {PIRSA:26040114 see, \url{https://scivideos.org/pirsa/26040114}}
          }
          

Abstract

The Jeans instability is a fundamental mechanism that explains how the initially almost uniform density of the early universe gave rise to collapsed structures—from molecular clouds and stars to galaxies and clusters. It also plays a key role in interpreting astrophysical probes such as the Lyman‑alpha forest seen in quasar spectra. In this talk, I will discuss how the classic Jeans instability is modified in the presence of dark matter (DM). I will show that when DM and baryons interact only through gravity and their relative drift is subsonic, a new resonant gravitational instability emerges—the Shalaby‑Broderick effect. I will outline efforts to identify observable signatures of this effect across a wide range of astrophysical systems, from planets and stars to galaxy clusters. On cosmological scales, probing this instability offers a direct test of the gravitational interaction between dark matter and baryons, and provides a unique window into DM perturbations on scales smaller than the baryonic Jeans scale—scales previously thought to be observationally inaccessible.