My research

I am a post-doc in the Department of Physics & Astronomy in Upenn, Philadelphia. I work in the cosmology group, supervised by Bhuvnesh Jain.

These are all my key words and interests:

large scale structure, growth of perturbations...
constraining dark matter, dark energy, and all the cosmological parameters...
helped by: large scale structure, cosmic microwave background, Integrated Sachs-Wolfe effect, redshift space distortions, baryon acoustic peak, lensing
using: big surveys such as SDSS, Luminous Red Galaxies


More detailed...

Physicists currently believe that the universe is composed basically of dark energy (70%) and dark matter (25%), both unknown components. The rest is made of known (baryonic) matter.
The standard cosmological model starts with Big Bang, followed by a rapid period of expansion of the universe called inflation. After that, tiny almost homogeneous fluctuations that conform the primordial universe, start to grow while universe expands now in a relatively slow rhythm. 380,000 years after the Big Bang, the temperature is low enough to make the universe become neutral after the recombination of atoms with electrons. Photons are almost free of interactions since then and reach us in the form of a Cosmic Microwave Background (CMB). We can measure the spatial anisotropy spectrum of CMB temperatures and compare it to the expected spectrum of acoustic oscillations. This comparison provides a direct geometrical test from which we can deduce that universe is flat or nearly flat. This can be explained if we introduce a new constituent in the universe apart from matter, the dark energy. Dark energy acts as anti-gravity that accelerates the expansion and is also observed through standard candles Supernovae Ia. Although there is a well motivate d model that can explain observations, neither dark matter nor dark energy are known elements, so it is important to use the large amount of newly available data to obtain tighter constraints on the constituents of the universe, the evolution of growth perturbations, the expansion history, and also other alternatives, such as modification of gravity at large scales.

I have been working with Luminous Red Galaxies from SDSS which trace dark matter (although biased) in a larger volume than normal galaxies, since they are brighter. I have looked at redshift space distortions, due to peculiar motion of galaxies, that distort the real-space isotropic correlation function. These distortions are one of the ways to study directly the growth of perturbations. I have also worked in the Integrated Sachs Wolfe effect (ISW), another direct way to study the growth trhough the evolution of gravitational potentials. ISW is detected when cross-correlating the CMB map with the LSS map which modifies these photons when passing through the evolving potentials. We can detect dark energy thanks to ISW, since we need a dark energy dominated universe to have an evolution of potentials. (although this could also be achieved by having a non-flat universe). LRG galaxies allow us to detect the baryon acoustic peak in the averaged correlation function, and if we detect it in the line-of-sight direction, it means a direct calculation of the Hubble constant! I have also worked with photometric surveys (angular projections, photometric redshifts).
In general, I am interested in any techinque that can contribute to a better understanding of our universe.
Here there are my works.



 

Publications

ADS publication list
Astro-ph archive

 

Talks and posters

Cross correlating WMAP with SDSS (poster)

Fitting dark matter with SDSS large structure (talk 2nd year PhD)

Covariance analysis and forecasts for DES (talk Collaboration Meeting DES Chicago Desember 2006)

PhD thesis: Large scale structure and dark energy (Barcelona, June 2008)