by
J.P. Uzan(CNRS, Institut d'Astrophysique de Paris)
→
Europe/Stockholm
Description
Fundamental constants are a cornerstone of our physical laws. Any
constant varying in space and/or time would reflect a violation of the
equivalence principle. Thus, it is of importance for our understanding of
gravity and of the domain of validity of general relativity to test for
their constancy.
I will first recall the relations between the constants, the tests of the
local position invariance and of the universality of free fall. I will
then sketch the main theoretical frameworks in which the low-energy
constants may actually be varying. Many experimental and observational
constraints have been obtained from atomic clocks, the Oklo phenomenon,
solar system observations, meteorite dating, quasar absorption spectra,
stellar physics, pulsar timing, the cosmic microwave background and big
bang nucleosynthesis. I will provide a summary of these observations.
To finish, cosmology, and in particular the models of the early universe,
allows to address the question of understanding their numerical values.
While very speculative, and probably out of reach of any experimental or
observational check, this may be the only insight to understand the
apparent fine-tuning that the constants seem to confront us with.
