Cosmology | IAS

I am Stephen Chen (陳師凡), a postdoctoral member at the Institute for Advanced Study. I recently obtained my PhD in the Physics Department at UC Berkeley working with Martin White. I am originally from a little island nation in the Pacific.

My research in cosmology is broadly focused on using the large-scale structure (LSS) of the universe to constrain fundamental physics. The universe is a complicated place! Much of my research focuses on modeling cosmological observables using effective field theories in order to robustly extract signatures of fundamental physics from the sea of other cool stuff going on–exploding stars, active black holes at the centers of galaxies, etc. While most of my work has involved the clustering of galaxies–I am an active member of the Dark Energy Spectroscopic Instrument–this work has also taken me to other places, like the Lyman alpha forest.

I am the author of the velocileptors code, which is a fast and Python-based perturbation theory code that works in Lagrangian and Eulerian perturbation theory to predict galaxy clustering in real and redshift space, configuration and Fourier space, as well as a bunch of related velocity statistics that might themselves lead to interesting cosmological constraints in the future. This code has a bunch of dinosaur cousins like spinosaurus and triceratops. I am also involved with anzu, an emulator for galaxy-lensing cross correlations led by Nick Kokron using a model proposed by me, Chirag Modi and Martin White combining the Lagrangian EFT prescription for galaxy bias and n-body simulations, and its updated version including massive neutrinos aemulus_heft with reduced nosie using Zeldovich Control Variates.

In a previous life I worked with Rob Simcoe and Paul Torrey on a survey of tiny gas clouds in the high-redshift universe. A full list of my publications can be found on ADS, arXiv or Google Scholar. My CV can be found here.