181 research outputs found
Gravitational Redshift, Equivalence Principle, and Matter Waves
We review matter wave and clock comparison tests of the gravitational
redshift. To elucidate their relationship to tests of the universality of free
fall (UFF), we define scenarios wherein redshift violations are coupled to
violations of UFF ("type II"), or independent of UFF violations ("type III"),
respectively. Clock comparisons and atom interferometers are sensitive to
similar effects in type II and precisely the same effects in type III
scenarios, although type III violations remain poorly constrained. Finally, we
describe the "Geodesic Explorer," a conceptual spaceborne atom interferometer
that will test the gravitational redshift with an accuracy 5 orders of
magnitude better than current terrestrial redshift experiments for type II
scenarios and 12 orders of magnitude better for type III.Comment: Work in progress. 11 page
Atom Interferometers and the Gravitational Redshift
From the principle of equivalence, Einstein predicted that clocks slow down
in a gravitational field. Since the general theory of relativity is based on
the principle of equivalence, it is essential to test this prediction
accurately. Muller, Peters and Chu claim that a reinterpretation of decade old
experiments with atom interferometers leads to a sensitive test of this
gravitational redshift effect at the Compton frequency. Wolf et al dispute this
claim and adduce arguments against it. In this article, we distill these
arguments to a single fundamental objection: an atom is NOT a clock ticking at
the Compton frequency. We conclude that atom interferometry experiments
conducted to date do not yield such sensitive tests of the gravitational
redshift. Finally, we suggest a new interferometric experiment to measure the
gravitational redshift, which realises a quantum version of the classical clock
"paradox".Comment: 18 pages, one figure, improved discussion, corrected typo
Phases and relativity in atomic gravimetry
The phase observable measured by an atomic gravimeter built up on stimulated
Raman transitions is discussed in a fully relativistic context. It is written
in terms of laser phases which are invariant under relativistic gauge
transformations. The dephasing is the sum of light and atomic contributions
which are connected to one another through their interplay with conservation
laws at the interaction vertices. In the case of a closed geometry, a compact
form of the dephasing is written in terms of a Legendre transform of the laser
phases. These general expressions are illustrated by discussing two techniques
used for compensating the Doppler shift, one corresponding to chirped
frequencies and the other one to ramped variations.Comment: 7 pages, 1 figur
Disrupting MLC1 and GlialCAM and ClC-2 interactions in leukodystrophy entails glial chloride channel dysfunction
Defects in the astrocytic membrane protein MLC1, the adhesion molecule GlialCAM or the chloride channel ClC-2 underlie human leukoencephalopathies. Whereas GlialCAM binds ClC-2 and MLC1, and modifies ClC-2 currents in vitro, no functional connections between MLC1 and ClC-2 are known. Here we investigate this by generating loss-of-function Glialcam and Mlc1 mouse models manifesting myelin vacuolization. We find that ClC-2 is unnecessary for MLC1 and GlialCAM localization in brain, whereas GlialCAM is important for targeting MLC1 and ClC-2 to specialized glial domains in vivo and for modifying ClC-2's biophysical properties specifically in oligodendrocytes (OLs), the cells chiefly affected by vacuolization. Unexpectedly, MLC1 is crucial for proper localization of GlialCAM and ClC-2, and for changing ClC-2 currents. Our data unmask an unforeseen functional relationship between MLC1 and ClC-2 in vivo, which is probably mediated by GlialCAM, and suggest that ClC-2 participates in the pathogenesis of megalencephalic leukoencephalopathy with subcortical cysts
Consistency analysis of a nonbirefringent Lorentz-violating planar model
In this work analyze the physical consistency of a nonbirefringent
Lorentz-violating planar model via the analysis of the pole structure of its
Feynman propagators. The nonbirefringent planar model, obtained from the
dimensional reduction of the CPT-even gauge sector of the standard model
extension, is composed of a gauge and a scalar fields, being affected by
Lorentz-violating (LIV) coefficients encoded in the symmetric tensor
. The propagator of the gauge field is explicitly evaluated
and expressed in terms of linear independent symmetric tensors, presenting only
one physical mode. The same holds for the scalar propagator. A consistency
analysis is performed based on the poles of the propagators. The isotropic
parity-even sector is stable, causal and unitary mode for .
On the other hand, the anisotropic sector is stable and unitary but in general
noncausal. Finally, it is shown that this planar model interacting with a
Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio
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