arXiv subjects

P. Viana

Publications and source records attributed to P. Viana.

2 recordsLinked to original sources

arXiv2003

WMAP Constraints on varying $α$ and the Promise of Reionization

We present up-to-date constraints on the value of the fine-structure constant at the epoch of decoupling from the recent observations made by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite. In the framework of models we considered, a positive (negative) variation of the value of $α$ at decoupling with respect to the present-day value is now bounded to be smaller than 2% (6%) at 95% confidence level. We point out that the existence of an early reionization epoch as suggested by the above measurements will, when more accurate cosmic microwave background polarization data is available, lead to considerably tighter constraints. The so-called `reionization bump', in particular, will be extremely useful for this purpose. We find that constraints on $α$ can in principle only be as small as $0.1 %$ using CMB data alone--tighter constraints will require further (non-CMB) priors.

astro-ph↗

arXiv2000

Looking for a varying $α$ in the Cosmic Microwave Background

We perform a likelihood analysis of the recently released BOOMERanG and MAXIMA data, allowing for the possibility of a time-varying fine-structure constant. We find that in general this data prefers a value of $α$ that was smaller in the past (which is in agreement with measurements of $α$ from quasar observations). However, there are some interesting degeneracies in the problem which imply that strong statements about $α$ can not be made using this method until independent accurate determinations of $Ω_b h^2$ and $H_0$ are available. We also show that a preferred lower value of $α$ comes mainly from the data points around the first Doppler peak, whereas the main effect of the high-$\ell$ data points is to increase the preferred value for $Ω_b h^2$ (while also tightening the constraints on $Ω_0$ and $H_0$). We comment on some implications of our results.

astro-ph↗