Causality constraints on corrections to the graviton threepoint coupling
Abstract
We consider higher derivative corrections to the graviton threepoint coupling within a weakly coupled theory of gravity. Lorentz invariance allows further structures beyond the one present in the Einstein theory. We argue that these are constrained by causality. We devise a thought experiment involving a high energy scattering process which leads to causality violation if the graviton threepoint vertex contains the additional structures. This violation cannot be fixed by adding conventional particles with spins J ≤ 2. But, it can be fixed by adding an infinite tower of extra massive particles with higher spins, J > 2. In AdS theories this implies a constraint on the conformal anomaly coefficients ac/c≲ 1/∆_{gap^2} n terms of ∆_{gap}, the dimension of the lightest single trace operator with spin J > 2. For inflation, or de Sitterlike solutions, it indicates the existence of massive higher spin particles if the gravity wave nongaussianity deviates significantly from the one computed in the Einstein theory.
 Publication:

Journal of High Energy Physics
 Pub Date:
 February 2016
 DOI:
 10.1007/JHEP02(2016)020
 arXiv:
 arXiv:1407.5597
 Bibcode:
 2016JHEP...02..020C
 Keywords:

 AdSCFT Correspondence;
 Models of Quantum Gravity;
 Classical Theories of Gravity;
 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology
 EPrint:
 50+22 pages, 13 figures