New experimental limit on the validity of local position invariance

Bauch, A.; Weyers, S.

doi:10.1103/physrevd.65.081101

Cited by 99 publications

(69 citation statements)

References 13 publications

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“…[7] (accounting for the result of ref. [20]), where a cryogenic microwave sapphire oscillator (CSO) was used. However, our work achieved this result with a measurement duration of 5 months compared to 6 years.…”

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confidence: 99%

Resonator with Ultrahigh Length Stability as a Probe for Equivalence-Principle-Violating Physics

2016

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In order to investigate the long-term dimensional stability of matter, we have operated an optical resonator fabricated from crystalline silicon at 1.5 K continuously for over one year and repeatedly compared its resonance frequency fres with the frequency of a GPS-monitored hydrogen maser. After allowing for an initial settling time, over a 163-day interval we found a mean fractional drift magnitude |f −1 res dfres/dt| < 1.4 × 10 −20 /s. The resonator frequency is determined by the physical length and the speed of light, and we measure it with respect to the atomic unit of time. Thus, the bound rules out, to first order, a hypothetical differential effect of the universe's expansion on rulers and atomic clocks. We also constrain a hypothetical violation of the principle of Local Position Invariance for resonator-based clocks and derive bounds for the strength of space-time fluctuations.In this paper we address experimentally the question about the intrinsic time-stability of the length of a macroscopic solid body. This question is related to the question about time-variation of the fundamental constants and effects of the expansion of the universe on local experiments. It may be hypothesized that, in violation of the Einstein Equivalence Principle (EP), the expansion affects the length of a block of solid matter and atomic energies to a different degree. The length, defined by a multiple of an interatomic spacing, can be measured by clocking the propagation time of an electromagnetic wave across it. This procedure effectively implements the Einstein light clock, or, in modern parlance, an electromagnetic resonator. The hypothetical differential effect would show up as a time-drift of the ratio of the frequency f res of an electromagnetic resonator and of an atomic (or molecular) transition (f atomic ). A resonator and an atom are dissimilar in the sense that the former's resonance frequency intrinsically involves the propagation of an electromagnetic wave, while the latter does not. Specifically, the time-drift would violate the principle of Local Position Invariance (LPI) of EP. The natural scale of an effect due to cosmological expansion, here the fractional drift rate The suitable regime in which to investigate the dimensional stability of matter is at cryogenic temperature, when the thermal expansion coefficient and the thermal energy content of matter are minimized. Ideally, during the cooling down and then permanence at cryogenic temperature, a stable energy minimum of the solid is reached. The expected high dimensional stability and the magnitude of H 0 lead to a challenging measurement problem: how to resolve tiny length changes, and how to suppress the influence of extrinsic disturbances. The problem can be addressed by casting the solid matter into an electromagnetic resonator of appropriate shape, by supporting it appropriately, and by measuring its resonance frequency using atomic time-keeping and frequency metrology instruments, which indeed permit ultra-high measurement precision and accur...

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confidence: 99%

Resonator with Ultrahigh Length Stability as a Probe for Equivalence-Principle-Violating Physics

2016

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“…The most sensitive current limits on k come from measurements of two Earth-bound clocks over the course of a year [2,[6][7][8][9][10][11][12]. The sensitivity is entirely due to ellipticity in Earth's orbit, which gives a 3% seasonal variation in the gravitational potential at Earth due to the Sun.…”

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confidence: 99%

Limits on the Dependence of the Fine-Structure Constant on Gravitational Potential from White-Dwarf Spectra

et al. 2013

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We propose a new probe of the dependence of the fine-structure constant on a strong gravitational field using metal lines in the spectra of white-dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white-dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits of Á = ¼ ð4:2 AE 1:6Þ Â 10 À5 and ðÀ6:1 AE 5:8Þ Â 10 À5 from FeV and NiV spectra, respectively, at a dimensionless gravitational potential relative to Earth of Á % 5 Â 10 À5 . With better determinations of the laboratory wavelengths of the lines employed these results could be improved by up to 2 orders of magnitude. DOI: 10.1103/PhysRevLett.111.010801 PACS numbers: 06.20.Jr, 31.15.am, 32.30.Jc, 97.20.Rp Light scalar fields can appear very naturally in modern cosmological models and theories of high-energy physics, changing parameters of the standard model such as fundamental coupling constants and mass ratios. Like the gravitational charge, the scalar charge is purely additive, so near massive objects such as white dwarfs the effect of the scalar field can change. For objects that are not too relativistic, such as stars and planets, both the total mass and the total scalar charge are simply proportional to the number of nucleons in the object. However, different types of coupling between the scalar field and other fields can lead to an increase or decrease in scalar coupling strengths near gravitating massive bodies [1]. For small variations, the scalar field variation at distance r from such an object of mass M is proportional to the change in dimensionless gravitational potential ¼ GM=rc 2 , and we express this proportionality by introducing the sensitivity parameter k [2]. Specifically, for changes in the fine-structure ''constant'' , we writeThis dependence can be seen explicitly in particular theories of varying , such as those of Bekenstein [3] and Barrow-Sandvik-Magueijo [4], and their generalizations [5], where can increase (Á = > 0) or decrease (Á = < 0) on approach to a massive object depending on the balance between electrostatic and magnetic energy in the ambient matter fields [1]. The most sensitive current limits on k come from measurements of two Earth-bound clocks over the course of a year [2,[6][7][8][9][10][11][12]. The sensitivity is entirely due to ellipticity in Earth's orbit, which gives a 3% seasonal variation in the gravitational potential at Earth due to the Sun. The peak-to-trough sinusoidal change in the potential has magnitude Á ¼ 3 Â 10 À10 . Each clock has a different sensitivity to variation, and so Á = can be measured and hence k extracted.Because of the high precision of atomic clocks, k is determined very precisely despite the relatively small seasonal change in the gravitational potential. By contrast, we examine a ''medium strength'' field, where Á is 5 orders of magnitude larger than in the Earth-bound experiments, and the distance between the probe and the source is $10 4 times smaller than 1 AU. This allows us to probe nonlinear coupling of Á...

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“…Here β1 and A very recent publication shows that the current best test for the Rb versus H is 4.9×10 --7 and Cs versus H is 1.1×10 --6 , so here we are 20 times and 4.4 times less sensitive respectively [17].…”

Section: A Search For Lpi Variations With Respect To Gravitational Pmentioning

confidence: 99%

Testing local position and fundamental constant invariance due to periodic gravitational and boost using long-term comparison of the SYRTE atomic fountains and H-masers

et al. 2013

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The frequencies of three separate Cs fountain clocks and one Rb fountain clock have been compared to various hydrogen masers to search for periodic changes correlated with the changing solar gravitational potential at the Earth and boost with respect to the Cosmic Microwave Background (CMB) rest frame. The data sets span over more than eight years. The main sources of long-term noise in such experiments are the offsets and linear drifts associated with the various H-masers. The drift can vary from nearly immeasurable to as high as 1.3×10 -15 per day. To circumvent these effects we apply a numerical derivative to the data, which significantly reduces the standard error when searching for periodic signals. We determine a standard error for the putative Local Position Invariance (LPI) coefficient with respect to gravity for a Cs-Fountain H-maser comparison of |β H −β Cs | ≤ 4.8×10 -6 and |β H −β Rb | ≤ 10 -5 for a Rb-Fountain H-maser comparison. From the same data the putative boost LPI coefficients were measured to a precision of up to parts in 10 11 with respect to the CMB rest frame. By combining these boost invariance experiments to a Cryogenic Sapphire Oscillator versus H-maser comparison 1 , independent limits on all nine coefficients of the boost violation vector with respect to fundamental constant invariance, € B α , € B e and € B q (fine structure constant, electron mass and quark mass respectively), were determined to a precision of parts up to 10 10 .

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New experimental limit on the validity of local position invariance

Cited by 99 publications

References 13 publications

Resonator with Ultrahigh Length Stability as a Probe for Equivalence-Principle-Violating Physics

Resonator with Ultrahigh Length Stability as a Probe for Equivalence-Principle-Violating Physics

Limits on the Dependence of the Fine-Structure Constant on Gravitational Potential from White-Dwarf Spectra

Testing local position and fundamental constant invariance due to periodic gravitational and boost using long-term comparison of the SYRTE atomic fountains and H-masers

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