High Energy Theory Lunchtime Seminar

We study deformations of the Randall--Sundrum 2 model with broken bulk Lorentz invariance. First, we prove a theorem which forbids a static smooth five-dimensional background to exist provided that null energy conditions for a matter on a brane and in a bulk are satisfied. However, if the Lorentz invariance is unbroken such a setup exists. Second, we derive perturbation spectra of scalar and spin-1/2 fermion particles in the backgrounds in question and show that, in spite of the full theory is manifestly not Lorentz invariant, the effective four-dimensional theory can be made approximately Lorentz invariant at low energies. We also investigate localization of particles on a brane in various scenarios with broken Lorentz invariance.