List of Figures
Figure 1:
Spectral representation of different models. (a) DGP (b) higherdimensional cascading gravity and (c) multigravity. Bigravity is the special case of multigravity with one massless mode and one massive mode. Massive gravity is the special case where only one massive mode couples to the rest of the standard model and the other modes decouple. (a) and (b) are models of soft massive gravity where the graviton mass can be thought of as a resonance. 

Figure 2:
Codimension2 brane with positive (resp. negative) tension brane leading to a positive (resp. negative) deficit angle in the two extra dimensions. 

Figure 3:
Sevendimensional cascading scenario and solution for one the metric potential on the dimensional brane in a 7dimensional cascading gravity scenario with tension on the dimensional brane located at , in the case where . and represent the two extra dimensions on the dimensional brane. Image reproduced with permission from [149], copyright APS. 

Figure 4:
Degrees of freedom for massive gravity on a maximally symmetric reference metric. The only theoretically allowed regions are the upper left green region and the line corresponding to GR. 

Figure 5:
Difference between phase, group, signal and front velocities. At , the phase and group velocities are represented on the left and given respectively by and (in the limit .) The signal and front velocity represented on the right are given by (where is the point where at least half the intensity of the original signal is reached.) The front velocity is given by . 

Figure 6:
Polarizations of gravitational waves in general relativity and potential additional polarizations in modified gravity. 

Figure 7:
Alternative ways in deriving the cosmology in massive gravity. 