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SYWS: Fundamentale Wechselwirkungen und ihre Symmetrien

SYWS 2: Fundamental Interactions and their Symmetries II

SYWS 2.2: Invited Talk

Wednesday, March 12, 2008, 16:30–17:00, 1A/B/C

The time Dependence of Fundamental Constants — •Thomas Udem — Max-Planck Institut für Quantenoptik Garching

Since Webb et al. [1] have detected a slightly smaller fine structure constant by quasar absorption spectra about 10 billion years ago an old idea of P.A.M. Dirac [2] from 1937 was revived. Using arguments philosophical in nature he speculated that fundamental constants should vary along with the expanding universe. For a long time the only possibility to search for these minute changes was to exploit the large look-back time of astronomical or geological observations. With the advent of frequency combs the possibility to check for these time variations in the laboratory with optical transitions in atoms, ions and molecules became readily available. Even though the time period covered by these laboratory measurements is typically 10 orders of magnitude shorter than for astronomical observations, they can be 10 orders of magnitude more accurate to provide comparable sensitivity. The question of the time dependence of fundamental constants is of high relevance in the context of modern cosmological models.

[1] J. K. Webb et al. Phys. Rev. Lett. 87, 091301 (2001).

[2] P.A.M. Dirac Nature, 139, 323 (1937).