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Register a new userImproved Tests of Lorentz Invariance in the Matter Sector using Atomic Clocks
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Added by
H\\'el\\`ene Pihan-Le Bars
Publication date
2017
fields
Physics
and research's language is
English
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For the purpose of searching for Lorentz-invariance violation in the minimal Standard-Model Extension, we perfom a reanalysis of data obtained from the $^{133}text{Cs}$ fountain clock operating at SYRTE. The previous study led to new limits on eight components of the $tilde{c}_{mu u}$ tensor, which quantifies the anisotropy of the proton kinetic energy. We recently derived an advanced model for the frequency shift of hyperfine Zeeman transition due to Lorentz violation and became able to constrain the ninth component, the isotropic coefficient $tilde{c}_{TT}$, which is the least well-constrained coefficient of $tilde{c}_{mu u}$. This model is based on a second-order boost Lorentz transformation from the laboratory frame to the Sun-centered frame, and it gives rise to an improvement of five orders of magnitude on $tilde{c}_{TT}$ compared to the state of the art.
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A more complete theoretical model of testing Lorentz violation by the comparison of atomic clocks is developed in the Robertson-Mansouri-Sexl kinematic framework. As this frame postulates the deviation of the coordinate transformation from the Lorentz transformation, from the viewpoint of the transformation violations on time and space, the LI violating effect in the atomic clock comparison can be explained as two parts: time-delay effect $alpha frac {v^2}{c^2}$ and structure effect $-frac {beta+2delta}{3} frac {v^2}{c^2}$. Standard model extension is a widely used dynamic frame to characterize the Lorentz violation, in which a space-orientation dependence violating background field is regarded as the essential reason for the Lorentz violation effect. Compared with the RMS frame which only indicates the kinematic properties with the coordinate transformation, this dynamic frame provides a more complete and clear description for the Lorentz violation effect.
High-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance, such as may be related to the structure of space-time near the Planck scale. I discuss the possible signatures of Lorentz invariance violation that can be manifested by observing the spectra, polarization, and timing of gamma-rays from active galactic nuclei and gamma-ray bursts. Other sensitive tests are provided by observations of the spectra of ultrahigh-energy cosmic rays and very high-energy neutrinos. I also discuss a new time-of-flight analysis of observations of GRB 090510 by the Fermi gamma-ray Space Telescope. These results, based on high-energy astrophysical observations, have fundamental implications for space-time physics and quantum gravity models.
We study the prospects for using interferometers in gravitational-wave detectors as tools to search for photon-sector violations of Lorentz symmetry. Existing interferometers are shown to be exquisitely sensitive to tiny changes in the effective refractive index of light occurring at frequencies around and below the microhertz range, including at the harmonics of the frequencies of the Earths sidereal rotation and annual revolution relevant for tests of Lorentz symmetry. We use preliminary data obtained by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2006-2007 to place constraints on coefficients for Lorentz violation in the photon sector exceeding current limits by about four orders of magnitude.
We report on a new experiment that tests for a violation of Lorentz invariance (LI), by searching for a dependence of atomic transition frequencies on the orientation of the spin of the involved states (Hughes-Drever type experiment). The atomic frequencies are measured using a laser cooled $^{133}$Cs atomic fountain clock, operating on a particular combination of Zeeman substates. We analyze the results within the framework of the Lorentz violating standard model extension (SME), where our experiment is sensitive to a largely unexplored region of the SME parameter space, corresponding to first measurements of four proton parameters and improvements by 11 and 13 orders of magnitude on the determination of four others. In spite of the attained uncertainties, and of having extended the search into a new region of the SME, we still find no indication of LI violation.
Current limits on violation of local Lorentz invariance in the photon sector are derived mainly from experiments that search for a spatial anisotropy in the speed of light. The presently operating gravitational wave detectors are Michelson interferometers with long effective arms, 4e5 m, and sensitive to a fringe shift 2e-9. Therefore they can be used to test for a difference in the speed of light in the two arms, as modulated bi-annualy by the orientation of the Earths velocity with respect to the direction of motion of the local system. A limit can be set on the Robertson-Mansouri-Sexl parameter PMM < 10e-15, as compared to its present limit of PMM < 2e-10, an improvement of five orders of magnitude.
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