I joined the Flatiron Institute in 2018 as a Senior Research Scientist in the
Center for Computational Astrophysics,
with a joint appointment at Stony Brook University. My
research focuses on theoretical and computational studies of planet formation and accretion disk processes, with
the primary goal of understanding the origins of the Solar System and extrasolar planetary systems. At CCA, with
Yan-Fei Jiang, I co-ordinate the activities of the Planet Formation group, and collaborate with Shirley Ho and
others on applications of Machine Learning to problems in planet formation and exoplanet dynamics. I am particularly excited by
ongoing CCA efforts to develop a next-generation performance portable hydrocode.
Current research
Planetary accretion and circumplanetary disks
The observation of accreting giant planets and a circumplanetary disk in the PDS 70 system opens new possibilities for
confronting planet formation models with data. With FRF Jiayin Dong, RS Yan-Fei Jiang, and multiple external collaborators, I
am working to understand the physics of how giant planets accrete and what we should expect for the structure and evolution of
circumplanetary disks. To address these questions, we are developing controlled numerical experiments that include subsets of
the relevant physics: magnetospheric accretion, radiation, and multi-fluid hydrodynamics. (Simulation image from Krapp et al. 2024)
Early phase planet formation
Understanding when and where dust particles are able to grow into planetesimals - macroscopic bodies of km-scale and larger - is
at the heart of developing predictive models for the overall architecture of planetary systems. My recent work in this area includes simulation studies of
the streaming instability for planetesimal formation, and work that explored the potential of Machine Learning in modeling the clustering of soild particles
in the two-phase turbulence of protoplanetary disks. With FRF Thomas Pfeil, we are working to couple particle coagulation / fragmentation physics with
radiation hydrodynamics to better understand what happens during these early phases of planet formation. (Image from Chan et al. 2024)
Accretion disk evolution
For both protoplanetary disks, and accretion disks around compact objects, the central question is to understand why disks evolve.
Turbulence - driven by instabilities such as the magnetorotational instability and self-gravity - and magnetized disk winds are both
viable processes. The Planet Formation group at CCA has advanced the state of the art in numerical simulations of multiple facets accretion disk physics, including
the Vertical Shear Instability, gravitational instability, and protoplanetary disk winds. Collaborating with observers, we have constrained the balance between turbulence and wind-driven angular momentum loss in driving the evolution of protoplanetary disks. In the high-energy realm, I have a longstanding interest
in the possibility that AGN and X-ray binary disks may be more strongly magnetized than has traditionally been assumed. Ongoing work is studying
the dynamics of such disks, including the consequences if the region of strong magnetization overlaps with radii where self-gravity and star formation set in. (Image from Armitage, in preparation)
