You must obey these three laws to join the group.


Chung-Pei's scientific work has been on theoretical and observational problems in extragalactic astronomy and cosmology. Four personae have been diagnosed for her multiple personality syndrome, although her graduate students and postdocs may report (and have induced) more identities:

  • The Smooth Side: During the first ten million years or so after the big bang, the fluctuations in matter and radiation in the universe remain small enough that they can be viewed as tiny ripples imprinted on a smooth background. The universe at this stage is well described by the linear cosmological perturbation theory, which Chung-Pei has investigated in some depth. This theory is specified by the coupled Einstein, Boltzmann, and fluid equations and is the foundation for many calculations in cosmology, e.g., the matter fluctuation power spectra and the temperature variations imprinted on the cosmic microwave background.

  • The Lumpy Side: A major challenge in theoretical cosmology today is in understanding how small initial fluctuations in matter and radiation in the smooth universe grow under gravitational instability into highly collapsed objects in the lumpy universe. Chung-Pei has been involved in designing and running large numerical N-body and hydrodynamical codes to simulate and study the nonlinear growth of dark matter and galaxies. She has developed new analytical techniques to better understand and model the nonlinear structure in the universe, including the halo model, kinetic theory for halo formation, and non-Markovian extension of the excursion set theory.

  • The Dark Side: The nature of dark matter remains one of the most intriguing unsolved mysteries in astronomy. Chung-Pei's interest has evolved from cold, to hot, to warm, and back to cold (but never lukewarm) dark matter, and has extended to dark energy. She makes detailed theoretical predictions for the impact of the dark sector on structure formation, and obtains constraints on the nature and abundance of dark matter and energy by comparing theory with observational results from, e.g., the high redshift universe and gravitational lenses.

  • The Bright Side: Chung-Pei has participated in a number of projects using telescopes such as Palomar and Keck. The projects include dynamical studies of superclusters, gravitational lensing studies of quasars and galaxy clusters, properties of distant galaxies, and weighing supermassive black holes. She is currently conducting an exciting survey named MASSIVE to study the most massive galaxies in the local universe.

    Graduate Students (to keep off the street)


    • Ryan Janish
    • Melanie Veale
    • Katelin Schutz
    • You? Come and chat

    Postdocs (to dine and wine)


    • Peter Behroozi (Hubble Fellow; Stanford PhD 2012)
    • Freeke van de Voort (TAC-ASIAA Fellow; Leiden PhD 2012)
    • Phillip Zukin (TAC-ASIAA Fellow; MIT PhD 2012)

    Former Team Members (and other diligent students who brightened my days or ate cookies at group meetings)