Rotating dual cryogenic sapphire oscillators with 10−16 fractional frequency stability for tests of Lorentz invariance

2011 ◽  
Author(s):  
Stephen Parker ◽  
Paul Stanwix ◽  
Michael Tobar ◽  
John Hartnett ◽  
Eugene Ivanov ◽  
...  
Keyword(s):  
Lorentz Invariance ◽  
Frequency Stability ◽  
Fractional Frequency

The fractional frequency stability of a 34-m-diameter beam-waveguide antenna

1994 ◽  
Vol 82 (5) ◽  
pp. 788-795 ◽  
Author(s):  
T.Y. Otoshi ◽  
M.M. Franco ◽  
G.F. Lutes
Keyword(s):  
Frequency Stability ◽  
Fractional Frequency ◽  
Beam Waveguide

scholarly journals A CPT-based Cs vapor cell atomic clock with a short-term fractional frequency stability of 3 x 10-13τ-1/2

2016 ◽  
Vol 723 ◽  
pp. 012013 ◽  
Author(s):  
Moustafa Abdel Hafiz ◽  
Xiaochi Liu ◽  
Stéphane Guérandel ◽  
Emeric De Clercq ◽  
Rodolphe Boudot
Keyword(s):  
Atomic Clock ◽  
Frequency Stability ◽  
Short Term ◽  
Vapor Cell ◽  
Fractional Frequency

GNSS time and frequency transfers through national positioning, navigation and timing infrastructure

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Thayathip Thongtan ◽  
Sivinee Sawatdiaree ◽  
Chalermchon Satirapod
Keyword(s):  
Time Scale ◽  
Frequency Stability ◽  
Frequency Offset ◽  
Internal Clock ◽  
Time Transfer ◽  
Time Zone ◽  
Common View ◽  
Standard Format ◽  
Fractional Frequency ◽  
Atomic Time

Abstract GNSS signals have been a practical time transfer tool to realise a Coordinated Universal Time (UTC) and set civilian clocks around the world with respect to this atomic time standard. UTC time scale is maintained by the International Bureau of Weights and Measurements (BIPM) adjusted to be close to a time scale based on the Earth’s rotation. In Thailand, the official atomic time clocks are maintained by the National Institute of Metrology Thailand (NIMT) to produce UTC(NIMT) and Thailand standard time which is always 7 hours ahead of UTC(NIMT) because of the time zone differences between Greenwich and Bangkok. National Positioning, Navigation and Timing (PNT) infrastructure comprises of GNSS geodetic receivers uniformly distributed to continually observe GNSS signals, mainly for geodetic survey applications both real-time and post-processing services. NIMT is involved in order to provide time link to UTC and to determine the characteristics of GNSS receiver internal clocks; namely, fractional frequency offset and frequency stabilities by applying the GNSS time transfer techniques of common-view algorithms. Monitored time differences with respect to UTC(NIMT) are achieved from selected 4 ground stations in different parts of the country with observations of 21 days in order to determine the frequency stability at 1-day and 7-day modes. GNSS standard log files; in RINEX format, at these receivers are transformed into a time transfer standard format; CGGTTS, used to compute the time differences between two stations, the fractional frequency offset and the frequency stability. Averaged fractional frequency offsets are 2.8 × 10 − 13 Hertz/Hertz 2.8\times {10^{-13}}\hspace{2.38387pt}\text{Hertz/Hertz} and computed Allan deviation is around 1.5 × 10 − 13 Hertz/Hertz 1.5\times {10^{-13}}\hspace{2.38387pt}\text{Hertz/Hertz} for an averaging time of 1 day. The comparison of the national time scale and receiver clock offsets of every receivers in this national GNSS PNT infrastructure could be accomplished through common-view time transfer using GNSS satellites to maintain the time link of geodetic active control points to UTC as well as to determine receiver internal clock characteristics.

Nonlocal Gravity

2017 ◽  
Author(s):  
Bahram Mashhoon
Keyword(s):  
Gravitational Field ◽  
Gravitational Lensing ◽  
Past History ◽  
Lorentz Invariance ◽  
Minkowski Spacetime ◽  
Field Measurements ◽  
Local Principle ◽  
History Of ◽  
Expansion Of The Universe ◽  
Nearby Galaxies

A postulate of locality permeates through the special and general theories of relativity. First, Lorentz invariance is extended in a pointwise manner to actual, namely, accelerated observers in Minkowski spacetime. This hypothesis of locality is then employed crucially in Einstein’s local principle of equivalence to render observers pointwise inertial in a gravitational field. Field measurements are intrinsically nonlocal, however. To go beyond the locality postulate in Minkowski spacetime, the past history of the accelerated observer must be taken into account in accordance with the Bohr-Rosenfeld principle. The observer in general carries the memory of its past acceleration. The deep connection between inertia and gravitation suggests that gravity could be nonlocal as well and in nonlocal gravity the fading gravitational memory of past events must then be taken into account. Along this line of thought, a classical nonlocal generalization of Einstein’s theory of gravitation has recently been developed. In this nonlocal gravity (NLG) theory, the gravitational field is local, but satisfies a partial integro-differential field equation. A significant observational consequence of this theory is that the nonlocal aspect of gravity appears to simulate dark matter. The implications of NLG are explored in this book for gravitational lensing, gravitational radiation, the gravitational physics of the Solar System and the internal dynamics of nearby galaxies as well as clusters of galaxies. This approach is extended to nonlocal Newtonian cosmology, where the attraction of gravity fades with the expansion of the universe. Thus far only some of the consequences of NLG have been compared with observation.

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