Gravitational probes of dark matter: off the beaten path

par Kfir Blum (weizmann institute of science)

jeudi 12 févr. 2026, 11:00 → 12:00 Europe/Paris

Auditorium Vivargent (LAPTh)

Many astrophysical and cosmological systems show compelling positive evidence for the existence of dark matter. Yet, as all of this positive evidence is based on gravitational effects, the fundamental particle nature of dark matter remains unknown, hidden behind the veil of the equivalence principle. I will discuss attempts to penetrate this veil, still focusing on gravitational dynamics alone. First, I consider ultralight dark matter, a regime that arises if dark matter particles are so light that their de-Broglie wavelength attains astronomical scales. Dark matter in this regime can be constrained by detailed analyses of stellar distributions in galaxies of various shapes and sizes, and can also leave an imprint in gravitational lensing observations. Second, I consider, more broadly, the phenomenon of gravitational dynamical friction, which offers a probe of dark matter beyond the mean-field level, and — in some systems — provides compelling new evidence for dark matter in galaxies, qualitatively different and independent from traditional stellar kinematics.