Cheng-Gang Shao

TianQin: a space-borne gravitational wave detector

TianQin is a proposal for a space-borne detector of gravitational waves in the millihertz frequencies. The experiment relies on a constellation of three drag-free spacecraft orbiting the Earth. Inter-spacecraft laser interferometry is used to monitor the distances between the test masses. The experiment is designed to be capable of detecting a signal with high confidence from a single source of gravitational waves within a few months of observing time. We describe the preliminary mission concept for TianQin, including the candidate source and experimental designs. We present estimates for the major constituents of the experiments error budget and discuss the projects overall feasibility. Given the current level of technology readiness, we expect TianQin to be flown in the second half of the next decade.

Search for Lorentz invariance violation through tests of the gravitational inverse square law at short-ranges

A search for sidereal variations in the non-Newtonian force between two tungsten plates separated at millimeter ranges sets experimental limits on Lorentz invariance violation involving quadratic couplings of Riemann curvature. We show that the Lorentz invariance violation force between two finite flat plates is dominated by the edge effects, which includes a suppression effect leading to lower limits than previous rough estimates. From this search, we determine the current best constraints of the Lorentz invariance violating coefficients at a level of

Combined search for Lorentz violation in short-range gravity

10^{-8}

Test of the Universality of Free Fall with Atoms in Different Spin Orientations

m

Feedback control of torsion balance in measurement of gravitational constant G with angular acceleration method

^{2}

Correlation method in period measurement of a torsion pendulum

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Determination of the limit of photon mass and cosmic magnetic vector with rotating torsion balance

Short-range experiments testing the gravitational inverse-square law at the submillimeter scale offer uniquely sensitive probes of Lorentz invariance. A combined analysis of results from the short-range gravity experiments HUST-2015, HUST-2011, IU-2012, and IU-2002 permits the first independent measurements of the 14 nonrelativistic coefficients for Lorentz violation in the pure-gravity sector at the level of 10^{-9}  m^{2}, improving by an order of magnitude the sensitivity to numerous types of Lorentz violation involving quadratic curvature derivatives and curvature couplings.

Preliminary determination of Newtonian gravitational constant with angular acceleration feedback method

We report a test of the universality of free fall by comparing the gravity acceleration of the ^{87}Rb atoms in m_{F}=+1 versus those in m_{F}=-1, of which the corresponding spin orientations are opposite. A Mach-Zehnder-type atom interferometer is exploited to alternately measure the free fall acceleration of the atoms in these two magnetic sublevels, and the resultant Eötvös ratio is η_{S}=(0.2±1.2)×10^{-7}. This also gives an upper limit of 5.4×10^{-6}  m^{-2} for a possible gradient field of the spacetime torsion. The interferometer using atoms in m_{F}=±1 is highly sensitive to the magnetic field inhomogeneity. A double differential measurement method is developed to alleviate the inhomogeneity influence, of which the effectiveness is validated by a magnetic field modulating experiment.

On the significance of the period fitting method

The performance of the feedback control system is of central importance in the measurement of the Newtons gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to [Formula: see text] at the signal frequency of 2 mHz, which contributes a [Formula: see text] uncertainty to the G value.

Enhanced sensitivity to Lorentz invariance violations in short-range gravity experiments

The correlation method is used to determine the period of a torsion pendulum. Calculation shows that this method cannot only suppress the disturbance of white noise, but it is also insensitive to drift and damping of the torsion pendulum. An estimate of the frequency based on this method is an approximative minimum variance unbiased estimator.