Do the laws of Nature vary with time?

PhD student Michael Murphy
PhD student Michael Murphy presenting the results of this research into the fine-structure constant.

Searches for temporal or spatial variations in the fundamental constants is presently an area of intense activity. A major goal for 2002 was to rigorously test our early results using a large sample of Keck spectra obtained by Prof. W. Sargent and his collaborators. We have now analysed about 100 high resolution Keck quasar spectra. These new results have now been reported in the literature. To our surprise, the new data are also consistent with a fine-structure constant, alpha, which is slightly smaller than the present day value. The statistical significance of the effect is high (about 6 sigma). Extensive statistical tests to try and identify systematic effects which could emulate a varying alpha have also been carried out but none have so far been found.

The project proved to be a very successful training ground for Michael Murphy, who completed his PhD at UNSW at the end of 2002 and has now moved to a postdoctoral appointment at the Institute of Astronomy in Cambridge.

A new postdoctoral research assistant, Dr. Panyayiotis Tzanivaris, who recently completed his PhD at the Cambridge IoA, has been appointed at UNSW to work on the ESO archive of quasar spectra obtained using UVES on the VLT.In parallel with the work on optical quasar spectra described above, Dr. Stephen Curran has been pursuing a different approach, developing radio astronomy methods to search for variations in a combination of constants, including alpha, gp (the proton g-factor), and me/mp, the ratio of the electron and proton masses.

In collaboration with Victor Flambaum and Vladimir Dmitriev, and my PhD student, Gabriel Mititelu, a new area has also arisen during the past year: using the light element abundances and theory to ask whether the deuteron binding strength Q was different at the time of Big Bang nucleosynthesis (BBN). We seem to have an astonishing new result: a slightly smaller value of Q at the epoch of BBN simultaneously reconciles 4He, 7Li and D observed abundances (which are otherwise discrepant), and renders agreement between the baryonic density parameters determined independently by BBN and the latest results from CMB measurements. This could be a coincidence, but it is a remarkable one if so.

John Webb




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