Do the Fundamental Constants of Nature Vary with Time and Distance?

School of Physics, University of NSW

3.30pm, Friday 8 February 2002, AR103 Seminar Room, Graduate Research Centre

Were the laws of nature the same ten billion light years away from us? A change in the fine structure constant ?=e²/hc could be detected via shifts in the rest wavelengths of resonance transitions in quasar absorption systems. We have developed a new approach which improves the sensitivity of this method by an order of magnitude (the effect that we study is 10 times larger than that studied in the previous works, see Phys. Rev. Lett. 82, 888, 1999). We have measured the fine structure constant in 140 absorption systems covering look-back times from 0.2 to 0.9 times the age of the Universe.

Theories unifying gravity with other interactions predict the spatial and temporal variation of the fundamental "constants" in the Universe. Current interest is high because in superstring theories, which have additional spatial dimensions compactified on tiny scales, any variation of the mean size of the extra dimensions results in changes of the 3-dimensional observed coupling constants. Also, we can now probe variations at the level predicted in inflationary models of the Universe.

Our initial results hinted that ? may have been smaller in the past (Phys. Rev. Lett., 82, 884, 1999). Startlingly, new results based on 3 independent data sets support the same effect (Phys. Rev. Lett. 87, 091301, 2001 and current work).

Recently we also obtained limits on cosmological variation of strong interaction and quark masses from Big Bang nucleosynthesis, quasar and laborataory spectra, and Oklo (natural nuclear reactor) data.

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