Future arcminute resolution polarization data from ground-based Cosmic Microwave Background (CMB) observations can be used to estimate the contribution to the temperature power spectrum from the primary anisotropies and to uncover the signature of re
ionization near $ell=1500$ in the small angular-scale temperature measurements. Our projections are based on combining expected small-scale E-mode polarization measurements from Advanced ACTPol in the range $300<ell<3000$ with simulated temperature data from the full Planck mission in the low and intermediate $ell$ region, $2<ell<2000$. We show that the six basic cosmological parameters determined from this combination of data will predict the underlying primordial temperature spectrum at high multipoles to better than $1%$ accuracy. Assuming an efficient cleaning from multi-frequency channels of most foregrounds in the temperature data, we investigate the sensitivity to the only residual secondary component, the kinematic Sunyaev-Zeldovich (kSZ) term. The CMB polarization is used to break degeneracies between primordial and secondary terms present in temperature and, in effect, to remove from the temperature data all but the residual kSZ term. We estimate a $15 sigma$ detection of the diffuse homogeneous kSZ signal from expected AdvACT temperature data at $ell>1500$, leading to a measurement of the amplitude of matter density fluctuations, $sigma_8$, at $1%$ precision. Alternatively, by exploring the reionization signal encoded in the patchy kSZ measurements, we bound the time and duration of the reionization with $sigma(z_{rm re})=1.1$ and $sigma(Delta z_{rm re})=0.2$. We find that these constraints degrade rapidly with large beam sizes, which highlights the importance of arcminute-scale resolution for future CMB surveys.
We discuss present and future cosmological constraints on variations of the fine structure constant $alpha$ induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism. We find that current cosmological
data show no variation of the fine structure constant at recombination respect to the present-day value, with $alpha$ / $alpha_0$ = 0.975 pm 0.020 at 95 % c.l., constraining the energy density in early dark energy to $Omega_e$ < 0.060 at 95 % c.l.. Moreover, we consider constraints on the parameter quantifying the strength of the coupling by the scalar field. We find that current cosmological constraints on the coupling are about 20 times weaker than those obtainable locally (which come from Equivalence Principle tests). However forthcoming or future missions, such as Planck Surveyor and CMBPol, can match and possibly even surpass the sensitivity of current local tests.
