Constructing Gravitational Dimensions

TL;DR

This paper investigates the challenges of constructing discrete gravitational dimensions from theories with multiple massive gravitons, highlighting fundamental limitations and exploring potential symmetries to achieve a local continuum limit.

Contribution

It demonstrates the impossibility of non-linear extensions for massive gravitons that maintain a local continuum limit and analyzes how discretization affects strong coupling scales and locality.

Findings

Single graviton theories break down at scale Lambda_3

Discretization influences the strong coupling scale and interactions

Candidate symmetries may help preserve locality in discretized models

Abstract

It would be extremely useful to know whether a particular low energy effective theory might have come from a compactification of a higher dimensional space. Here, this problem is approached from the ground up by considering theories with multiple interacting massive gravitons. It is actually very difficult to construct discrete gravitational dimensions which have a local continuum limit. In fact, any model with only nearest neighbor interactions is doomed. If we could find a non-linear extension for the Fierz-Pauli Lagrangian for a graviton of mass mg which does not break down until the scale Lambda_2=(mg Mpl)^(1/2), this could be used to construct a large class of models whose continuum limit is local in the extra dimension. But this is shown to be impossible: a theory with a single graviton must break down by Lambda_3 = (mg^2 Mpl)^(1/3). Next, we look at how the discretization prescribed by the truncation of the KK tower of an honest extra diemsinon rasies the scale of strong coupling. It dictates an intricate set of interactions among various fields which conspire to soften the strongest scattering amplitudes and allow for a local continuum limit. A number of canditate symmetries associated with locality in the discretized dimension are also discussed.