Holographic Self-Tuning of the Cosmological Constant
By Francesco Nitti (APC)
Thursday 15 Mar
Place: Aula 507 (Pere Pascual)
I will present a brane-world setup, based on the gauge/gravity duality, in which the four-dimensional cosmological constant is neutralized by a dynamical self-adjustment mechanism. The model consists in a five-dimensional Einstein-Dilaton gravity coupled to a four-dimensional brane on which ordinary matter and gauge fields are localized. The brane position in the bulk is determined dynamically by the junction conditions, and flat-brane solutions exist for generic values of the brane vacuum energy. A regime with emergent 4-dimensional gravity is possible, due to the presence of an induced gravity term on the brane. The emergent 4d graviton acquires an effective mass, and a five-dimensional regime may exist at large and/or small scales. Analysis of scalar fluctuations allows to formulate conditions for perturbative stability of the flat solutions, which can be met in a broad range of the model parameters.