Signatures of a Graviton Mass in the Cosmic Microwave Background

There exist consistent low energy effective field theories describing gravity in the Higgs phase that allow the coexistence of massive gravitons and the conventional 1/r potential of gravity. In an effort to constrain the value of the graviton mass in these theories, we study the tensor contribution to the CMB temperature anisotropy and polarization spectra in the presence of a non-vanishing graviton mass. We find that the observation of a B-mode signal consistent with the spectrum predicted by inflationary models would provide the strongest limit yet on the mass of an elementary particle -- a graviton -- at a level of m\lesssim 10^(-30) eV\approx(10 Mpc)^(-1). We also find that a graviton mass in the range between (10 Mpc)^(-1) and (10 kpc)^(-1) leads to interesting modifications of the polarization spectrum. The characteristic signature of a graviton mass in this range would be a plateau in the B-mode spectrum up to angular multipoles of l\sim 100. For even larger values of the graviton mass the tensor contribution to the CMB spectra becomes strongly suppressed.