Coagulation Instability in Protoplanetary Disks: A Novel Mechanism Connecting Collisional Growth and Hydrodynamical Clumping of Dust Particles

We present a new instability driven by combination of coagulation and radial drift dust particles. refer to this as ``coagulation instability" regard it promising mechanism concentrate particles assist planetesimal formation in the very early stages disk evolution. Because dust-density dependence collisional efficiency, efficiently (inefficiently) grow region positive (negative) density perturbations, which lead small variation sizes result velocity perturbations. The resultant perturbations concentration amplify This feedback makes unstable. growth timescale is few tens orbital periods even when dust-to-gas mass ratio order $10^{-3}$. In protoplanetary disk, tend depletion. locally concentrates such dust-depleted region. resulting provides preferable sites for dust-gas instabilities develop, leads further concentration. Dust diffusion aerodynamical stabilize short-wavelength modes, but do not completely suppress instability. Therefore, expected play an important role setting up next stage other develop toward formation, streaming or secular gravitational