Exotic accretion disks could betray boson stars in alternative gravity

Thick accretion disks around rotating boson stars behave very differently when the underlying gravity theory allows spontaneous scalarization. Without an innermost stable circular orbit, infalling matter can spiral all the way to the center, producing quasi-spherical, tightly bound disks. For the most massive scalarized solutions, a non-monotonic angular momentum profile even allows a double-centered disk connected by a cusp—a configuration impossible around ordinary compact objects in GR. These distinctive disk geometries could, in principle, be identified through future high-resolution imaging or spectral observations of candidate boson-star systems.