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## Varying Fundamental Constants |

The deepest
enigma of modern physics is whether or not there are any fundamental scalar
fields in nature. Although there are widely accepted theories in particle
physics and cosmology which rely on them, neither side has so far produced any
direct and definitive evidence. On the other hand, Einstein gravity does not
contain any scalar fields. This is a very remarkable fact, because almost any
consistent gravitational theory that one can think of will have them. Recent
developments suggest that scalar fields are just as important in cosmology.
Among other roles, they are the preferred explanation for the recently claimed
variations of what have been considered fundamental constants of nature.
Varying fundamental constants
directly map the dynamics of the underlying cosmological scalar
fields, and the large redshift lever arm afforded by
a range of observational techniques in astrophysics and cosmology combined
with local laboratory measurements can
be used to optimally probe gravity on large and small scales, as well as
providing crucial indirect clues on the presence of extra dimensions and
ultimately string theory itself. Varying
fundamental constants are part of ESA and ESO science drivers for next
generation of facilities, so closer interactions between theorists,
observational astronomers, cosmologists and atomic physicists will be crucial
for progress in the field. There are controversial claims of a 5-sigma
detection of a smaller value of the fine-structure constant, and of a 3-sigma detection
of a larger value of the electron-to-proton mass ratio, which are contradicted
by analyses of other groups. Meanwhile laboratory measurements find null
results, as do other astrophysical probes. Given the potential implications, it
is important to shed light on this controversy.
Confirmation
of these variations would immediately imply a violation of the Einstein
Equivalence Principle, signalling the breakdown of
the concept of gravity as geometry and pointing to yet undiscovered gravitational
physics. We will bring
together representatives from the key groups working on this topic, to devise a
strategy for a thorough inter-disciplinary study of varying constants,
combining theoretical expectations and predictions, astrophysical observations
(from the ground and space) and local experiments (mostly with atomic clocks,
either in ground laboratories or in microgravity). [Back] |