>> Interests << Publications

I am a cosmologist working on very early Universe Cosmology and Dark energy. More precisely, my main research interests cover

• Dark Energy and the CC Problem: Particle physics theories typically predict the presence of a vacuum energy, at worst of the order of the Planck mass M_Pl ~ 10⁷²GeV⁴, which would cause the Universe to accelerate with a Hubble parameter H ~ 10⁶¹km/s Mpc, or at best of the order of the supersymmetry breaking scale M_susy ~ TeV⁴. Since this is clearly incompatible with observations, physicists have for a long time assumed that some symmetry sets this vacuum energy to zero. However, in 1998, observations of type Ia supernovae measured for the first time the acceleration of the Universe with precision, corresponding to a Hubble parameter of order H ~ 70km/s Mpc, i.e. consistent with a cosmological constant of order 10⁴⁸GeV⁴, that is 120 orders of magnitude smaller than predicted from particle physics. This measurement was soon confirmed by many other sources, such as the CMB, matter density and gravitational lensing and is to date arguably the most embarrassing puzzle of modern cosmology.
• Cosmological Perturbations: The power spectrum and non-gaussianities present in the Cosmic Microwave Background provide strong signatures of models of brane inflation.
  
  Click here for a list of papers on the subject.
• Modified / Massive Gravity: A potential idea to tackle the cosmological constant problem, is to weaken the effect the vacuum energy has on the geometry by modifying gravity at large distances (of the order of the Hubble scale today). Effectively this is possible the graviton was massive or had resonance.
  
  This is the idea behind the degravitation model suggested by N. Arkani-Hamed, S. Dimopoulos, G. Dvali and G. Gabadadze, in 2002 and by G. Dvali, S. Hofmann, and J. Khoury, in 2007
• SLED: The SLED, or Supersymmetric Large extra dimensions, first proposed by Y. Aghababaie, C. Burgess, S. Parameswaran and F. Quevedo in 2003 provides another potential resolution to the Naturalness Problem of the Cosmological Constant using two compactified supersymmetric extra dimensions of submillimeter size, hence potentially tackling the gauge hierarchy problem.
  
  See Cliff Burgess's review
• EFT of codimension-2 objects: Exploring the effective physics for observers localized on codimension-2 branes or cosmic string and understanding the consequences for the Hierarchy problem and the Cosmological Constant problem.

Bio: In January 2012, I will be joining the Particle/Astrophysics Group at Case Western Reserve University as an Assistant Professor. Currently I am an FNS assistant professor in the Cosmology group at Geneva University. Before that I was a joint postdoctoral Researcher at the Perimeter Institute and at McMaster University, and postdoc at McGill University. I obtained my PhD in 2005 in Cambridge University, UK.