## Séminaire de Physique Théorique

**Radiation in presence of extra dimenions**

Dmitry Gal'tsov (Univerity of Moscow + LAPP Annecy)

Friday 14 December 2012 14:00 - Tours - Salle 1180 (Bât E2)

**Résumé :**

We discuss production of soft Kaluza-Klein gravitons in collision of point-like particles (partons) at energies exceeding the multidimensional Palck mass in TeV scale gravity with toroidal extra dimensions. In this regive gravity becomes a dominant force and it classicalizes opening the way to compute radiation (quasi)classically. Various approaches to do this exist applicable for different impact parameters, such as eikonal approximation, classical radiation in (multidimensional) Schwarzschild, post-linear expansions on the Minkowski background. For close to head-on collisions the radiation losses constitute up to half of the initial energy, the rest forming the black hole. For larger impact parameters radiation losses increase and become the dominant dissipative factor. Radiation efficiency depends crucially on the number of extra dimensions, since the number of soft Kaluza-Klein mode increases fast. Using multidimensional generalization of the post-linear expansion shceme of GR we show that with more than two extra dimensions radiation becomes so strong that radiation reaction force has to taken into aacount in describing collisions in the no-black hole region.

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