Constraints on Modified Gravity from ACT and SPT
  The Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) have
recently provided new and precise measurements of the Cosmic Microwave
Background anisotropy damping tail. This region of the CMB angular spectra,
thanks to the angular distortions produced by gravitational lensing, can probe
the growth of matter perturbations and provide a test for general relativity.
Here we make use of the ACT and SPT power spectrum measurements (combined with
the recent WMAP9 data) to constrain f(R) gravity theories. Adopting a
parametrized approach, we obtain an upper limit on the lengthscale of the
theory of B_0 < 0.86 at 95% c.l. from ACT, while we get a significantly
stronger bound from SPT with B_0 < 0.14 at 95% c.l..
