174 research outputs found
Comment on "Global Positioning System Test of the Local Position Invariance of Planck's Constant"
In their Letter, Kentosh and Mohageg [Phys. Rev. Lett. 108, 110801 (2012)]
seek to use data from clocks aboard global positioning system (GPS) satellites
to place limits on local position invariance (LPI) violations of Planck's
constant, h. It is the purpose of this comment to show that discussing limits
on variation of dimensional constants (such as h) is not meaningful; that even
within a correct framework it is not possible to extract limits on variation of
fundamental constants from a single type of clock aboard GPS satellites; and to
correct an important misconception in the authors' interpretation of previous
Earth-based LPI experiments.Comment: Reply to article available here: arXiv:1203.010
Astronomical and laboratory searches for space-time variation of fundamental constants
We review recent activity searching for variations in the fundamental
constants of nature in quasar absorption spectra and in the laboratory. While
research in this direction has been ongoing for many decades, the topic has
recently been stimulated by astronomical evidence for spatial variation in the
fine-structure constant, alpha. This result could be confirmed using different
quasar data and atomic clock measurements, but there are significant challenges
to obtain the required accuracy. We review existing measurements and discuss
some of the most promising systems where any variations would be strongly
enhanced.Comment: Invited review talk (Flambaum) at ICAP 2010, Cairns, Australi
Search for variation of fundamental constants and violations of fundamental symmetries using isotope comparisons
Atomic microwave clocks based on hyperfine transitions, such as the caesium
standard, tick with a frequency that is proportional to the magnetic moment of
the nucleus. This magnetic moment varies strongly between isotopes of the same
atom, while all atomic electron parameters remain the same. Therefore the
comparison of two microwave clocks based on different isotopes of the same atom
can be used to constrain variation of fundamental constants. In this paper we
calculate the neutron and proton contributions to the nuclear magnetic moments,
as well as their sensitivity to any potential quark mass variation, in a number
of isotopes of experimental interest including 201,199Hg and 87,85Rb, where
experiments are underway. We also include a brief treatment of the dependence
of the hyperfine transitions to variation in nuclear radius, which in turn is
proportional to any change in quark mass. Our calculations of
expectation-values of proton and neutron spin in nuclei are also needed to
interpret measurements of violations of fundamental symmetries.Comment: 7 page
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