C. J. A. P. Martins

Constraints on the CMB temperature redshift dependence from SZ and distance measurements

The relation between redshift and the CMB temperature, TCMB(z) = T0(1+z) is a key prediction of standard cosmology, but is violated in many non-standard models. Constraining possible deviations to this law is an effective way to test the ΛCDM paradigm and search for hints of new physics. We present state-of-the-art constraints, using both direct and indirect measurements. In particular, we point out that in models where photons can be created or destroyed, not only does the temperature-redshift relation change, but so does the distance duality relation, and these departures from the standard behaviour are related, providing us with an opportunity to improve constraints. We show that current datasets limit possible deviations of the form TCMB(z) = T0(1+z)1−β to be β = 0.004±0.016 up to a redshift z ~ 3. We also discuss how, with the next generation of space and ground-based experiments, these constraints can be improved by more than one order of magnitude.

Probing unification scenarios with atomic clocks

We discuss the usage of measurements of the stability of nature’s fundamental constants coming from comparisons between atomic clocks as a means to constrain coupled variations of these constants in a broad class of unification scenarios. After introducing the phenomenology of these models, we provide updated constraints based on a global analysis of the latest experimental results. We obtain null results for the proton-to-electron mass ratio ??/?=(0.68±5.79)×10-16??yr-1 and for the gyromagnetic factor g?p/gp=(-0.72±0.89)×10-16??yr-1 (both of these being at the 95% confidence level). These results are compatible with theoretical expectations on unification scenarios, but much freedom exists due to the presence of a degeneracy direction in the relevant parameter space.

Fine structure constant and the CMB damping scale

The recent measurements of the Cosmic Microwave Background anisotropies at arc minute angular nscales performed by the ACT and SPT experiments are probing the damping regime of CMB fluctuations. nThe analysis of these data sets unexpectedly suggests that the effective number of relativistic degrees of nfreedom is larger than the standard value of Neff ¼ 3:04, and inconsistent with it at more than two standard ndeviations. In this paper we study the role of a mechanism that could affect the shape of the CMB angular nfluctuations at those scales, namely, a change in the recombination process through variations in the fine nstructure constant. We show that the new CMB data significantly improve the previous constraints on nvariations of �, with �=�0 ¼ 0:984 � 0:005, i.e. hinting also at a more than two standard deviation from nthe current, local, value �0. A significant degeneracy is present between � and Neff, and when variations in nthe latter are allowed the constraints on � are relaxed and again consistent with the standard value. nDeviations of either parameter from their standard values would imply the presence of new, currently nunknown physics

Consistency tests of the stability of fundamental couplings and unification scenarios

We test the consistency of several independent astrophysical measurements of fundamental dimensionless constants. In particular, we compare direct measurements of the fine-structure constant

Analytic models for the evolution of semilocal string networks

ensuremath{alpha}

Cosmic string evolution with a conserved charge

and the proton-to-electron mass ratio

Evolution of hybrid defect networks

ensuremath{mu}={m}_{p}/{m}_{e}

Current and future constraints on Bekenstein-type models for varying couplings

(mostly in the optical/ultraviolet) with combined measurements of

Fine-structure constant constraints on Bekenstein-type models

ensuremath{alpha}

Models for small-scale structure of cosmic strings: Mathematical formalism

,