Séminaire / Seminar GReCO |
| « Exploring the cosmological observations for signatures of extra dimensions » |
|
G. Geshnizjani |
| I present a case that current observations may already indicate new gravitational physics on cosmological scales. I argue that in models with infinite-volume (or, at least, cosmological-size) extra dimensions, the longitudinal mode of the graviton mediates an extra scalar force which speeds up structure formation at late times, thereby can give rise to observable signatures. On the other hand the excess of power seen in the Lyman-? forest and small-scale CMB experiments, the anomalously large bulk flows seen both in peculiar velocity surveys and in kinetic SZ, and the higher ISW cross-correlation may also be indicating that structure has been more evolved than expected from ?CDM. Moreover, with certain assumptions about the behavior of the longitudinal mode on super-Hubble scales, our modified gravity framework can also alleviate the tension with the low quadrupole and the peculiar vanishing of the CMB correlation function on large angular scales, seen both in COBE and WMAP. This relies on a novel mechanism that cancels a late-time ISW contribution against the primordial Sachs-Wolfe amplitude. |
|
lundi 22 février 2010 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |