Violation Of Local Position Invariance Research Articles

Time keeping and searching for new physics using metastable states of Cu, Ag, and Au

We study the prospects of using the electric quadrupole transitions from the ground states of Cu, Ag and Au to the metastable state $^2{\rm D}_{5/2}$ as clock transitions in optical lattice clocks. We calculate lifetimes, transition rates, systematic shifts, and demonstrate that the fractional uncertainty of the clocks can be similar to what is achieved in the best current optical clocks. The use of these proposed clocks for the search of new physics, such as time variation of the fine structure constant, search for low-mass scalar dark matter, violation of Local Position Invariance and violation of Lorenz Invariance is discussed.

Improved Limits for Violations of Local Position Invariance from Atomic Clock Comparisons.

We compare two optical clocks based on the ^{2}S_{1/2}(F=0)→^{2}D_{3/2}(F=2) electric quadrupole (E2) and the ^{2}S_{1/2}(F=0)→^{2}F_{7/2}(F=3) electric octupole (E3) transition of ^{171}Yb^{+} and measure the frequency ratio ν_{E3}/ν_{E2}=0.932829404530965376(32), improving upon previous measurements by an order of magnitude. Using two caesium fountain clocks, we find ν_{E3}=642121496772645.10(8) Hz, the most accurate determination of an optical transition frequency to date. Repeated measurements of both quantities over several years are analyzed for potential violations of local position invariance. We improve by factors of about 20 and 2 the limits for fractional temporal variations of the fine structure constant α to 1.0(1.1)×10^{-18}/yr and of the proton-to-electron mass ratio μ to -8(36)×10^{-18}/yr. Using the annual variation of the Sun's gravitational potential at Earth Φ, we improve limits for a potential coupling of both constants to gravity, (c^{2}/α)(dα/dΦ)=14(11)×10^{-9} and (c^{2}/μ)(dμ/dΦ)=7(45)×10^{-8}.

New limits on the violation of local position invariance of gravity

Within the parameterized post-Newtonian (PPN) formalism, there could be an anisotropy of local gravity induced by an external matter distribution, even for a fully conservative metric theory of gravity. It reflects the breakdown of the local position invariance of gravity and, within the PPN formalism, is characterized by the Whitehead parameter ξ. We present three different kinds of observation, from the Solar system and radio pulsars, to constrain it. The most stringent limit comes from recent results on the extremely stable pulse profiles of solitary millisecond pulsars, that gives (95% CL), where the hat denotes the strong-field generalization of ξ. This limit is six orders of magnitude more constraining than the current best limit from superconducting gravimeter experiments. It can be converted into an upper limit of ∼4 × 10−16 on the spatial anisotropy of the gravitational constant.Communicated by C M Will

Transverse gravity versus observations

Theories of gravity invariant under those diffeomorphisms generated by transverse vectors, ∂μξμ = 0 are considered. Such theories are dubbed transverse, and differ from General Relativity in that the determinant of the metric, g, is a transverse scalar. We comment on diverse ways in which these models can be constrained using a variety of observations. Generically, an additional scalar degree of freedom mediates the interaction, so the usual constraints on scalar-tensor theories have to be imposed. If the purely gravitational part is Einstein-Hilbert but the matter action is transverse, the models predict that the three a priori different concepts of mass (gravitational active and gravitational passive as well as inertial) are not equivalent anymore. These transverse deviations from General Relativity are therefore tightly constrained, actually correlated with existing bounds on violations of the equivalence principle, local violations of Newton's third law and/or violation of Local Position Invariance.

Variation of fundamental constants in space and time: Theory and observations

Review of recent works devoted to the temporal and spatialvariation of the fundamental constants and dependence of the fundamentalconstants on the gravitational potential (violation of local position invariance) is presented. We discuss the variation of the fine structure constant α=e2/ħc, strong interaction andfundamental masses (Higgs vacuum), e.g. the electron-to-proton mass ratioμ=me/Mp or Xe=me/ΛQCD and Xq=mq/ΛQCD.We also present new results from Big Bang nucleosynthesisand Oklo natural nuclear reactor data and propose new measurements of enhanced effects in atoms, nuclei and molecules, both in quasar and laboratory spectra.

VARIATION OF THE FUNDAMENTAL CONSTANTS: THEORY AND OBSERVATIONS

Review of recent works devoted to the variation of the fine structure constant α, strong interaction and fundamental masses (Higgs vacuum) is presented. The results from Big Bang nucleosynthesis, quasar absorption spectra, and Oklo natural nuclear reactor data give us the space-time variation on the Universe lifetime scale. Comparison of different atomic clocks gives us the present time variation. Assuming linear variation with time we can compare different results. The best limit on the variation of the electron-to-proton mass ratio μ = me/Mp and Xe = me/ΛQCD follows from the quasar absorption spectra:1[Formula: see text]. A combination of this result and the atomic clock results2,3 gives the best limt on variation of [Formula: see text]. The Oklo natural reactor gives the best limit on the variation of Xs = ms/ΛQCD where ms is the strange quark mass:4,5[Formula: see text]. Note that the Oklo data can not give us any limit on the variation of α since the effect of α there is much smaller than the effect of Xs and should be neglected. Huge enhancement of the relative variation effects happens in transitions between close atomic, molecular and nuclear energy levels. We suggest several new cases where the levels are very narrow. Large enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feshbach resonance. How changing physical constants and violation of local position invariance may occur? Light scalar fields very naturally appear in modern cosmological models, affecting parameters of the Standard Model (e.g. α). Cosmological variations of these scalar fields should occur because of drastic changes of matter composition in Universe: the latest such event is rather recent (about 5 billion years ago), from matter to dark energy domination. Massive bodies (stars or galaxies) can also affect physical constants. They have large scalar charge S proportional to number of particles which produces a Coulomb-like scalar field U = S/r. This leads to a variation of the fundamental constants proportional to the gravitational potential, e.g. δα/α = kαδ(GM/rc2). We compare different manifestations of this effect. The strongest limits6kα + 0.17ke = (-3.5 ±6) × 10-7 and kα + 0.13kq = (-1 ± 17) × 10-7 are obtained from the measurements of dependence of atomic frequencies on the distance from Sun2,7 (the distance varies due to the ellipticity of the Earth's orbit).

Testing the equivalence principle by Lamb shift energies.

The Einstein equivalence principle has as one of its implications that the nongravitational laws of physics are those of special relativity in any local freely falling frame. We consider possible tests of this hypothesis for systems whose energies are due to radiative corrections, i.e., which arise purely as a consequence of quantum field theoretic loop effects. Specifically, we evaluate the Lamb shift transition (as given by the energy splitting between the $2{S}_{\frac{1}{2}}$ and $2{P}_{\frac{1}{2}}$ atomic states) within the context of violations of local position invariance and local Lorentz invariance, as described by the $\mathrm{TH}\ensuremath{\epsilon}\ensuremath{\mu}$ formalism. We compute the associated redshift and time dilation parameters, and discuss how (high-precision) measurements of these quantities could provide new information on the validity of the equivalence principle.