Maths HEP Lunchtime Seminars: Extra dimensional self-tuning of the vacuum energy: obstructions and ways around
15 December 2017 13:00 in CM221
Gravitational models of self-tuning are those in which vacuum energy has no observable effect on spacetime curvature even though it is a priori unsuppressed below the cut-off, thereby avoiding the cosmological constant problem. We study a class of six dimensional braneworld models that implement self-tuning by decoupling vacuum energy from the gravitational sector induced on the brane. Special care is taken to come up with a consistent core model that resolves the brane as cylindrical vorton carrying charge and current. By studying the setup in a thin-wall approximation for vanishing charge, we find that phenomenological constraints push the theory into a pathological parameter regime. In the second part, we will propose a model independent analysis of self-tuning based on a spectral decomposition of the exchange amplitude for conserved sources of energy-momentum. This provides us with a deeper understanding of the failure of the extra dimensional model and allows us to identify new obstructions to self-tuning, complementing a famous no-go theorem by Weinberg. Finally, we search for novel ways around our obstructions and highlight different interesting possibilities.