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| 2. |
- Thompson, Rodger I., et al.
(författare)
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A molecular probe of dark energy
- 2008
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Ingår i: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 42:3, s. 596-598
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Tidskriftsartikel (refereegranskat)abstract
- Many theoretical models of dark energy invoke rolling scaler fields which in turn predict time varying values of the fundamental constants. Establishing the value of the fundamental constants at various times in the universe can probe and test the various dark energy theories. One of the constants that is predicted to vary is the ratio of the electron to proton mass μ. It was established early on that molecular spectra are sensitive to the value of μ and can be used as probes of that value. This article describes the use of the spectrum of molecular hydrogen in high redshift Damped Lyman Alpha systems (DLAs) as a sensitive probe of the time evolution of μ.
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| 3. |
- Thompson, Rodger I., et al.
(författare)
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An observational determination of the proton to electron mass ratio in the early Universe
- 2009
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 703:2009 October 1, s. 1648 - 1662
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to resolve the discrepancy between two measurements of the fundamental constant μ, the proton to electron mass ratio, at early times in the universe we reanalyze the same data used in the earlier studies. Our analysis of the molecular hydrogen absorption lines in archival Very Large Telescope/Ultraviolet and Visible Echelle Spectrometer (UVES) spectra of the damped Lyman alpha systems in the quasi-stellar objects Q0347-383 and Q0405-443 yields a combined measurement of a Δμ/μ value of (–7 ± 8) × 10–6, consistent with no change in the value of μ over a time span of 11.5 Gyr. Here, we define Δμ as (μ z – μ0) where μ z is the value of μ at a redshift of z and μ0 is the present-day value. Our null result is consistent with the recent measurements of King et al., Δμ/μ = (2.6 ± 3.0) × 10–6, and inconsistent with the positive detection of a change in μ by Reinhold et al. Both of the previous studies and this study are based on the same data but with differing analysis methods. Improvements in the wavelength calibration over the UVES pipeline calibration is a key element in both of the null results. This leads to the conclusion that the fundamental constant μ is unchanged to an accuracy of 10–5 over the last 80% of the age of the universe, well into the matter dominated epoch. This limit provides constraints on models of dark energy that invoke rolling scalar fields and also limits the parameter space of supersymmetric or string theory models of physics. New instruments, both planned and under construction, will provide opportunities to greatly improve the accuracy of these measurements.
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