Brane Effects on Extra Dimensional Scenarios: A Tale of Two Gravitons
M. Carena, A. Delgado, J. Lykken, S. Pokorski, M. Quiros, C. E. M. Wagner
TL;DR
This work analyzes gravity in a brane-world with a brane-localized kinetic term, introducing infrared and ultraviolet cutoffs to regulate the theory. By computing the brane propagator on a $(4+d)$-D bulk and examining both infinite and finite extra-dimensional radii, the authors show that infinite flat spaces with $d\ge 2$ generically produce a light massive graviton that conflicts with known gravity tests, while finite-$R$ scenarios yield a two-graviton spectrum: a massless graviton with standard couplings and a second, heavier state with much stronger coupling, capable of substantially altering collider and table-top phenomenology. The analysis connects the IR and UV behaviors through explicit expressions for the propagator and resonance scales $\mathcal{M}_d$ and $\gamma_d$, highlighting how the brane term can reshape ADD predictions and providing concrete bounds on model parameters from table-top data. Overall, the paper clarifies under which conditions brane-induced gravity can mimic or deviate from four-dimensional gravity and how such effects could be tested experimentally.
Abstract
We analyze the propagation of a scalar field in multidimensional theories which include kinetic corrections in the brane, as a prototype for gravitational interactions in a four dimensional brane located in a (nearly) flat extra dimensional bulk. We regularize the theory by introducing an infrared cutoff given by the size of the extra dimensions and a physical ultraviolet cutoff of the order of the fundamental Planck scale in the higher dimensional theory. We show that, contrary to recent suggestions, the radius of the extra dimensions cannot be arbitrarily large. Moreover, for finite radii, the gravitational effects localized on the brane can substantially alter the phenomenology of collider and/or table-top gravitational experiments. This phenomenology is dictated by the presence of a massless graviton, with standard couplings to the matter fields, and a massive graviton which couples to matter in a much stronger way. While graviton KK modes lighter than the massive graviton couple to matter in a standard way, the couplings to matter of the heavier KK modes are strongly suppressed.