Open AccessMeasuring α in the early Universe: cosmic microwave background polarization, re‐ionization and the Fisher matrix analysis
Author(s) -
Rocha G.,
Trotta R.,
Martins C. J. A. P.,
Melchiorri A.,
Avelino P. P.,
Bean R.,
Viana P. T. P.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07832.x
Subject(s) - physics , cosmic microwave background , cmb cold spot , planck , cosmic variance , cosmic background radiation , astrophysics , spectral index , astronomy , quantum mechanics , spectral line , anisotropy
We present a detailed analysis of present and future cosmic microwave background (CMB) constraints of the value of the fine‐structure constant, α. We carry out a more detailed analysis of the WMAP first‐year data, deriving state‐of‐the‐art constraints on α and discussing various other issues, such as the possible hints for the running of the spectral index. We find, at 95 per cent confidence level, that 0.95 < α dec /α 0 < 1.02 . Setting d n S /d ln k = 0 yields 0.94 < α dec /α 0 < 1.01 as previously reported. We find that a lower value of α dec /α 0 makes a value of d n S /d ln k = 0 more compatible with the data. We also perform a thorough Fisher matrix analysis (including both temperature and polarization, as well as α and the optical depth τ), in order to estimate how future CMB experiments will be able to constrain α and other cosmological parameters. We find that Planck data alone can constrain τ with an accuracy of the order 4 per cent and that this constraint can be as small as 1.7 per cent for an ideal cosmic variance limited (CVL) experiment. Constraints on α are of the order of 0.3 per cent for Planck and can in principle be as small as 0.1 per cent using CMB data alone: tighter constraints will require further (non‐CMB) priors.