Tests Of Local Lorentz Invariance Research Articles

Local Lorentz Invariance Tests for Photons and Hadrons at the Gamma Factory

AbstractHigh‐precision tests of local Lorentz invariance, via monitoring of the sidereal time variation of the photon energies emitted by ultrarelativistic heavy‐ion beams and of the beam momentum, are proposed. This paper includes descriptions of the physics ideas and the concept for the detector. The experiment results will allow high‐precision tests of LLI via anisotropy of the maximum attainable speed of a photon and an ion. The projected accuracy for the asymmetries interpreted in the framework of the anisotropic relativistic mechanics corresponds to the limit on sidereal time variation of the one‐way maximum attainable speed at the levels between 10−14 and 10−17.

ACES/PHARAO: high-performance space-to-ground and ground-to-ground clock comparison for fundamental physics

The Atomic Clock Ensemble in Space is a fundamental physics mission of the European Space Agency to be launched in August 2021. It relies on a high-performance clock onboard the International Space Station (ISS), a network of high-performance clocks on ground, a dedicated 2-way microwave link (MWL) enabling space-to-ground and ground-to-ground clock comparisons, as well as an optical link (ELT). PHARAO/SHM (Projet d’Horloge Atomique par Refroidissement d’Atomes en Orbite/Space Hydrogen Maser), the clock onboard the ISS, has a relative frequency accuracy at the \({10}^{-16}\) level, a relative frequency stability (Allan deviation) equal to \({10}^{-13}/\sqrt{\tau }\) (\(\tau\) being the integration time in seconds) and a time deviation of 12 picoseconds after one day of integration. The MWL is designed to reach a time deviation below 7 ps after one day of integration. While space-to-ground clock comparisons will enable precise tests of the gravitational redshift, tests of deviations from General Relativity at the \({10}^{-6}\) level, and tests of local Lorentz invariance at the \({10}^{-10}\) level, ground-to-ground clock comparisons will enable a search of the time variation of fundamental constants with uncertainty at the \({10}^{-17}\) level after one year. In this contribution, we review the mission setup with a particular emphasis on the MWL, discuss the simulation and data analysis software developed to investigate mission performance, focusing on its primary scientific objective: the test of the gravitational redshift.

Coherent Excitation of the Highly Forbidden Electric Octupole Transition in Yb+172

We report on the first coherent excitation of the highly forbidden ^{2}S_{1/2}→^{2}F_{7/2} electric octupole (E3) transition in a single trapped ^{172}Yb^{+} ion, an isotope without nuclear spin. Using the transition in ^{171}Yb^{+} as a reference, we determine the transition frequency to be 642 116 784 950 887.6(2.4) Hz. We map out the magnetic field environment using the forbidden ^{2}S_{1/2}→^{2}D_{5/2} electric quadrupole (E2) transition and determine its frequency to be 729 476 867 027 206.8(4.4) Hz. Our results are a factor of 1×10^{5} (3×10^{5}) more accurate for the E2 (E3) transition compared to previous measurements. The results open up the way to search for new physics via precise isotope shift measurements and improved tests of local Lorentz invariance using the metastable ^{2}F_{7/2} state of Yb^{+}.

The Confrontation between General Relativity and Experiment.

The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.

New tests of local Lorentz invariance of gravity with small-eccentricity binary pulsars

Some alternative gravity theories allow the Universal matter distribution to single out the existence of a preferred frame, which breaks the symmetry of local Lorentz invariance (LLI) for the gravitational interaction. In the post-Newtonian parametrization of semi-conservative gravity theories, LLI violation is characterized by two parameters, α1 and α2. In binary pulsars, the isotropic violation of Lorentz invariance in the gravitational sector should lead to characteristic preferred frame effects (PFEs) in the orbital dynamics, if the barycenter of the binary is moving relative to the preferred frame with a velocity w. For small-eccentricity binaries, the effects induced by and (the hat indicates possible modifications by strong-field effects) decouple, and can therefore be tested independently. We use recent timing results of two compact pulsar-white dwarf binaries with known three-dimensional velocity, PSRs J1012+5307 and J1738+0333 to constrain PFEs for strongly self-gravitating bodies, by assuming the isotropic cosmic microwave background to single out a preferred frame. The time derivative of the projected semi-major axis is used to constrain a precession of the orbital plane around w due to PFEs. From this, we derive a limit at 95% confidence level, which is the most constraining limit for strongly self-gravitating systems up to now, however, still three orders of magnitude weaker than the best Solar system limit for the corresponding weak-field parameter α2. Concerning , we propose a new, robust method to constrain this parameter, which avoids the probabilistic considerations inherent in previous methods. This method is based on the fact that a PFE-induced intrinsic eccentricity cannot stay unobserved during a long-term observation due to the significant precession of periastron in binary pulsar with short orbital periods. Our most conservative result, at 95% confidence level from PSR J1738+0333, constitutes a significant improvement compared to current most stringent limits obtained both in the Solar system and binary pulsar tests. We also derive corresponding limits for and for a preferred frame that is at rest with respect to our Galaxy, and preferred frames that locally co-move with the rotation of our Galaxy. These limits will continue to improve significantly with future pulsar timing observations conducted at large radio telescopes.Communicated by C M Will

Atom interferometry tests of local Lorentz invariance in gravity and electrodynamics

We present atom-interferometer tests of the local Lorentz invariance of post-Newtonian gravity. An experiment probing for anomalous vertical gravity on Earth, which has already been performed by us, uses the highest-resolution atomic gravimeter so far. The influence of Lorentz violation in electrodynamics is also taken into account, resulting in combined bounds on Lorentz violation in gravity and electrodynamics. Expressed within the standard model extension or Nordtvedt's anisotropic universe model, we limit twelve linear combinations of seven coefficients for Lorentz violation at the part per billion level, from which we derive limits on six coefficients (and seven when taking into account additional data from lunar laser ranging). We also discuss the use of horizontal interferometers, including atom-chip or guided-atom devices, which potentially allow the use of longer coherence times in order to achieve higher sensitivity.

Testing the Einstein equivalence principle: Atomic clocks and local Lorentz invariance.

Three recent, remarkably sharp experimental tests of local Lorentz invariance are founded on an analysis of the electrostatic structure of atoms and nuclei moving through a nonmetric gravitational field. In this paper we extend this analysis to account for hyperfine and other relativistic aspects of atomic structure. One product of this work is a new quantitative interpretation of experimental tests of local Lorentz invariance that employ hydrogen-maser clocks, clocks whose ticking rates are governed by an atomic hyperfine transition. The analytical methods developed in this paper constitute a fairly complete set of tools for studying the breakdown of local Lorentz invariance in Lagrangian-based nonmetric theories of gravitation.

Testing Local Lorentz Invariance using laboratory and space technology

We present a theoretical framework for discussing experimental tests of Local Lorentz Invariance. In contrast to earlier kinematical approaches to tests of special relativity, this framework is dynamical in nature. Based on a formalism for analyzing non-metric theories of gravity, it treats in detail the behavior of rods, clocks, and other devices in motion relative to any preferred universal frame singled out by Lorentz non-invariant dynamics. Observable deviations from Lorentz invariance are determined by the size of a parameter δ ≡ ( c −2 − 1), where c is the speed of light in the preferred frame relative to the limiting speed of test particles. If Lorentz invariance holds, δ = 0. Previous tests of local lorentz invariance have set such upper limits as |δ| < 10 −4 (Michelson-Morley experiment), |δ| < 10 −16 (Hughes-Drever experiment), and |δ| < 3 × 10 −22 (trapped atoms experiments). We describe new tests, involving atomic clocks and the NASA Deep Space Network, and involving gyroscopes, and discuss the possible constraints they would provide.