Extreme parameter sensitivity in quasidilaton massive gravity
Abstract
We reanalyze the behavior of FriedmannLemaîtreRobertsonWalker cosmologies in the recently proposed quasidilaton massivegravity model, and discover that the background dynamics present hitherto unreported features that require unexpected finetuning of the additional fundamental parameters of the theory for an observationally consistent background cosmology. We also identify new allowed regions in the parameter space and exclude some of the previously considered ones. The evolution of the mass of gravitational waves reveals nontrivial behavior, exhibiting a masssquared that may be negative in the past, and that presently, while positive, is larger than the square of the Hubble parameter, H_{0}^{2} . These properties of the gravitywave mass have the potential to lead to observational tests of the theory. While quasidilaton massive gravity is known to have issues with stability at short distances, the current analysis is a first step toward the investigation of the more stable extended quasidilaton massivegravity theory, with some expectation that both the finetuning of parameters and the interesting behavior of the gravitywave mass will persist.
 Publication:

Physical Review D
 Pub Date:
 October 2015
 DOI:
 10.1103/PhysRevD.92.084033
 arXiv:
 arXiv:1506.01000
 Bibcode:
 2015PhRvD..92h4033A
 Keywords:

 98.80.k;
 95.36.+x;
 04.50.Kd;
 Cosmology;
 Dark energy;
 Modified theories of gravity;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 10 pages, 7 figures