The first measurements of acoustic peaks in the CMB anisotropies have confirmed that the birth of fluctuations may have taken place during an early inflationary era of the universe. In this domain, our activities deal with the construction of explicit models of inflation as well as the extraction of their observable consequences. Our fields of expertise comprise some actively debated subjects as the trans-Planckian problem, inflation with non-minimally coupled scalar fields, DBI- and brane inflation as in the context of String Theory (KKLMMT models). For all these systems, we are maintaining various numerical tools to compute the relevant observables required for comparison with CMB data. Special attention is devoted to the class of multi-field inflationary models. The hybrid mechanism is expected to be realized within high energy particle physics models whereas Higgs inflation is a candidate of choice for TeV scale inflation.
External collaborators: Jérôme Martin (Institut d'Astrophysique de Paris, France), Sébastien Clesse (Cambridge University, U.K.).
Although the undergoing cosmic acceleration may be explained by a non-vanishing cosmological constant in Einstein gravity, various dynamical effects could very well explain current observations, all dubbed as dark energy. Quintessence, as a light scalar field minimally coupled to gravity, is a dark energy candidate to explain the recent acceleration of the Universe expansion. The Ratra-Peebles potential and its corrected form in supergravity are under study. Using a modified version of CAMB, including perturbations of the scalar field, we use the latest SNIa and CMB observations to select acceptable points in the parameter space. Starting with the associated matter power spectrum, in collaboration with the LUTh (Paris-Meudon Obs., France) we run N-body simulations of growth of large scale structures where the background evolution is modified by quintessence. We are involved in the Dark Energy Universe Simulation Series (DEUSS) collaboration. Another dark energy candiate involves cosmic inflation, currently the best explanation of the origin of large scale structures and CMB anisotropies. Similarly, if dark energy is a light scalar field, the current acceleration can be the consequence of quantum fluctuations during cosmic inflation, provided this one occurs at TeV scale.
External collaborators: Jean-Michel Alimi, Yann Rasera, Pier Stefano Corasaniti (Observatoire de Paris-Meudon, France). Teruaki Suyama (The University of Tokyo, Japan), Tomo Takahashi (Saga University, Japan), Masahide Yamaguchi (Tokyo Institute of Technology, Japan), Shuichiro Yokoyama (Nagoya University, Japan).
