I am a postdoctoral research fellow at the Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP) at Columbia University. My research includes dark energy, the future lifetime of the universe, inflation, and reheating after inflation. Currently my main focus is on weak lensing from N-body simulations. Other computational methods I have applied are in particular lattice simulations of the early universe and Markov Chain Monte Carlo (MCMC) techniques for cosmological parameter estimation from various observations. See my list of publications for details. Among the large computer clusters used are the McKenzie Cluster at CITA, the LSST Cluster at the Brookhaven National Laboratory, and the computational centers of TeraGrid.

My further interests include aviation, sports, photography, traveling, backpacking, and various others.

The author in an ASK-21 over the Swiss Alps.

Emitted by distant galaxies in the far reaches of the universe, light gets bent as it passes large galaxy clusters and its path is deflected. Also altered is the apparent shape of these distant galaxies. Not knowing the intrinsic ellipticities of the latter ones, one can still statistically make powerful predictions about the matter distribution of the universe by measuring these distortions.

Measuring the distortions in convergence and shear maps is an art of its own. Inferring information about the intervening matter distribution another. In order to interpret these maps properly, one can simulate various matter distributions and the resulting patterns in maps. Unlike the observations, the simulations give access to the full three-dimensional matter distribution between the distant galaxies and the observer, and thus provide an invaluable tool to teach us how to interpret the weak lensing maps and reach the correct cosmological conclusions.

The simulations are conducted with N-body codes, which simulate the gravitational interactions of some 10^8 particles, each representing a matter clump many orders of magnitude larger than the mass of our sun. The clustering of matter is followed throughout the expansion of the universe until the present day, and later analyzed with ray-tracing codes and other tools to create the weak lensing maps.

A typical weak lensing map (convergence) from an N-body simulation.

You may contact me by email at my work address elsewhere on the Columbia website (it will not be reproduced here to avoid spam). To facilitate your search, here is a direct link to my alternate email address, which is being forwarded to my work address.