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Planet formation within protoplanetary disks presents an array of unsolved questions, two of which I aim to address in this talk.

First, I'll explore how dust is concentrated to densities sufficiently high for the on-set of planetesimal formation. By drawing a parallel to the formation of underwater sand ripples, I introduce a novel linear, axisymmetric instability capable of transforming turbulent dust regions in a disk's mid-plane into dense, azimuthally stretched filaments. This process hinges on a rapid decrease in diffusivity with heightened dust concentration, a premise supported by our numerical simulations where dust-gas interactions self-generate turbulent diffusion.

Second, I will discuss planet-hosting (wide) binary systems, where recent studies suggest a prevalence of coplanar arrangement of planetary and binary orbits. I propose that this alignment, along with observed obliquity distributions in exoplanetary systems, can be attributed to viscous dissipation in the disk during binary-driven precession. Moreover, our analysis predicts that the alignment tendency should weaken as the binary stellar mass ratio increases, and indeed, I will present new evidence for this trend in TESS data of exoplanet-hosting binaries.