Cheng -Gang Shao

• Professor
• Huazhong University of Science and Technology

Lorentz symmetry is a cornerstone of both the General relativity and Standard Model and its experimental verification deepens our understanding of nature. This paper focuses on the investigation of Lorentz violations with the context of clock comparison experiments in the framework of Standard Model Extension (SME). Considering matter-gravity coupl...

The exploration of the surrounding world and the universe is an important theme in the legacy of humankind. The detection of gravitational waves is adding a new dimension to this grand effort. What are the fundamental physical laws governing the dynamics of the universe? What is the fundamental composition of the universe? How has the universe evol...

General relativity (GR) is a highly successful theory that describes gravity as a geometric phenomenon. The gravitational redshift, a classic test of GR, can potentially be violated in alternative gravity theories, and experimental tests on this effect are crucial for our understanding of gravity. In this paper, considering the space-ground clock c...

TianQin is a future space-based gravitational wave observatory targeting the frequency window of $10^{-4}$ Hz $\sim 1$ Hz. A large variety of gravitational wave sources are expected in this frequency band, including the merger of massive black hole binaries, the inspiral of extreme/intermediate mass ratio systems, stellar-mass black hole binaries,...

Gravitational waves (GWs) have six possible polarization modes, and whose successful detection can effectively test the gravitational properties under the strong field theory and help distinguish between different theories of gravity. Space-based GW detectors can respond differently to different polarization modes and can be used to measure the pol...

Local Lorentz invariance is an important foundation of General Relativity, and its high-precision testing can help to explore the unified theories. In this work, we focus on the local Lorentz violating effect in pure gravity with mass dimension d = 6, and study the experimental design for testing local Lorentz violation with precision torsion pendu...

Arm-locking technique has been a focus of attention as one of the means to suppress the laser phase noise in space-based gravitational wave detector. The main idea of the arm-locking technique is to transfer the stability of the detector arm length to laser frequency by introducing a feedback control loop. Generally, laser phase noise will be suppr...

Short-range gravity experiments are more suitable for the testing of high-order Lorentz symmetry breaking effects. In our previous work, we proposed a new experimental design based on precision torsion balance technology to test the Lorentz violation force effect that varies inversely with the fourth power of distance (corresponding to mass dimensi...

Space gravitational wave detection primarily focuses on the rich wave sources corresponding to the millihertz frequency band, which provide key information for studying the fundamental physics of cosmology and astrophysics. However, gravitational wave signals are extremely weak, and any noise during the detection process could potentially overwhelm...

Laser interferometry plays a crucial role in laser ranging for high-precision space missions such as GRACE (Gravity Recovery and Climate Experiment) Follow-On-like missions and gravitational wave detectors. For such accuracy of modern space missions, a precise relativistic model of light propagation is required. With the post-Newtonian approximatio...

Phase-locking configuration was proposed as a baseline optical implementation for the space-borne gravitational wave detectors. By assigning one laser as the reference, termed the master, the remaining five lasers, dubbed slaves, are no longer free-running but phase-locked to form a master-slave arrangement. As a baseline optical implementation for...

We conduct numerical investigations on the critical collapse of spherically symmetric massless scalar fields in asymptotically anti-de Sitter spacetime. Our primary focus is on the behavior of the critical amplitude under various initial configurations of the scalar field. Through our numerical results, we obtain a formula that determines the criti...

In the black hole perturbation theory framework, two different physical pictures for echoes in compact objects have been proposed. The first mechanism interprets echoes as repeated reflections of gravitational waves within a potential well, where the echo period is defined by twice the distance related to the spatial displacement operator that sepa...

Thermal noise in the mirror coatings limits the accuracy of today’s most optical precision measurement experiments. Unlike the more commonly discussed thermal phase noise, the crystalline coating can generate thermal birefringent noise due to its anisotropic nature. In this study, we propose that the nondiagonal anisotropic photoelastic effect indu...

The Eötvös-type torsion balance is a well-known gravity gradient instrument for the regional or local geophysical exploration. As a key issue for the gravity gradient measurement, the estimation of the systematic effects in the instrument is rarely discussed as yet. This lack may lead to inconsistencies in the actual gravity gradient measurements....

The laser interferometer space antenna (LISA) uses laser interferometry to measure gravitational wave-induced distance changes between freely falling test masses on separate spacecraft. In practice, the space-borne gravitational wave detector operates in a plasma medium, and subsequently, the variations in electron density affect the refractive ind...

We study the dynamics of critical collapse of a spherically symmetric scalar field. Approximate analytic expressions for the metric functions and matter field in the large-radius region are obtained. It is found that due to the boundary conditions at the center, in the central region, the equation of motion for the scalar field is reduced to the fl...

Loop quantum gravity, as one branch of quantum gravity, holds the potential to explore the fundamental nature of black holes. Recently, according to the quantum Oppenheimer-Snyder model in loop quantum cosmology, a novel loop quantum corrected black hole in de Sitter spacetime has been discovered. Here, we first investigate the corresponding quasin...

While general relativity predicts only two tensor modes for gravitational-wave (GW) polarization, general metric theories of gravity allow for up to four additional modes, including two vector and two scalar modes. Observing the polarization modes of GWs could provide a direct test of the modified gravity. The stochastic GW background (SGWB), which...

We study the collisions of two scalar wave packets in the asymptotically flat spacetime and asymptotically anti–de Sitter spacetime in spherical symmetry. An energy transfer formula is obtained, y=Cmimo/r, where y is the transferred energy in the collisions of the two wave packets; mi and mo are the Misner-Sharp energies for the ingoing and outgoin...

In the short-range test of the gravitational inverse-square law (ISL) using a torsion pendulum, the residual electrostatic force is usually the major disturbance. We have built a torsion pendulum apparatus to verify the coupling effect of the residual electrostatic force with the separation variation between the test mass and the shielding membrane...

We study the energy issue in critical collapse. It is found that in critical collapse, the contribution from the material energy is greater than that from the gravitational energy. The quantity m/r plays an important role in identifying the formation of apparent horizon in gravitational collapse, where m is the Misner-Sharp mass and r the areal rad...

Time delay interferometry (TDI) is often utilized in the data preprocessing of space-based gravitational wave detectors, primarily for suppressing laser frequency noise. About 20 years ago, assuming arm lengths remain constant over time, researchers presented comprehensive mathematical descriptions for the first-generation and modified first-genera...

Lorentz symmetry (LS), one of the most fundamental physical symmetries, has been extensively studied in the context of quantum gravity and unification theories. Many of these theories predict a LS violation, which could arise from the discreteness of spacetime, or extra dimensions. Standard-model extension (SME) is an effective field theory to desc...

A fine gravitational theory is essentially expected to deal with the problem of spacetime singularities. Loop quantum gravity as one branch of quantum gravity is potential to explore the nature of black holes. Recently, according to the quantum Oppenheimer-Snyder model in loop quantum cosmology, a novel loop quantum corrected black hole in de Sitte...

Time delay interferometry (TDI) is primarily proposed for space-borne heterodyne interferometers to suppress the intrinsic laser phase noise. According to the TDI algorithm, the targeted sensitivity is achieved by constructing a virtual equal-arm interferometer through a linear combination of appropriately time-shifted independent Doppler measureme...

Time Delay Interferometry (TDI) is often utilized in the data pre-processing of space-based gravitational wave detectors, primarily for suppressing laser frequency noise. About twenty years ago, assuming armlengths remain constant over time, researchers presented comprehensive mathematical descriptions for the first-generation and modified first-ge...

We study the dynamics of critical collapse of a spherically symmetric scalar field. Approximate analytic expressions for the metric functions and matter field in the large-radius region are obtained. It is found that because of the boundary conditions at the center, in the central region, the equation of motion for the scalar field is reduced to th...

Future space-based gravitational-wave detectors will detect gravitational waves with high sensitivity in the millihertz frequency band, which provides more opportunities to test theories of gravity than ground-based ones. The study of quasinormal modes (QNMs) and their application to testing gravity theories have been an important aspect in the fie...

Inspired by the combinatorial algebraic approach proposed by Dhurandhar et al., we propose two novel classes of second-generation time-delay interferometry (TDI) solutions and their further generalization. The primary strategy of the algorithm is to enumerate specific types of residual laser frequency noise associated with second-order commutators...

Future space-based gravitational-wave detectors will detect gravitational waves with high sensitivity in the millihertz frequency band, which provides more opportunities to test theories of gravity than ground-based ones. The study of quasinormal modes (QNMs) and their application to testing gravity theories have been an important aspect in the fie...

The metrological characteristics of source masses are essential in the determination of the Newtonian gravitational constant G. This paper presents an air-bearing method to check the density uniformity of spherical source masses by measuring the mass center offset from the geometric center. With detailed error analysis, we find that the eccentricit...

In the electromagnetic channel, chaotic gravitational lensing is a peculiar phenomenon in strong gravitational lensing. In this work, we analyze the properties and emergence of chaotic gravitational lensing in the Manko-Novikov black hole spacetime. Aiming to understand better the underlying physics, we elaborate on the boundaries of the accessib...

The squeeze-film-damping effect is one of the main limits in many precision experiments, especially in the study of short-range interactions, and its physical mechanism is still not very clear. We develop a torsion pendulum to measure the damping effects caused by the thermal motion of residual gas between a cubic test mass and a pair of symmetric...

The residual gas damping in the enclosure surrounding a free-fall test mass is an important limiting factor for the sensitivity of some space detection missions. We present a constrained volume damping model for space-borne gravitational wave detection, which depends on the escape time needed for a molecule to diffuse out of the gap between two adj...

The spatial variation and temporal variation in surface potential are important error sources in various precision experiments and deserved to be considered carefully. In the former case, the theoretical analysis shows that this effect depends on the surface potentials through their spatial autocorrelation functions. By making some modification to...

Einstein’s general relativity theory provides a successful understanding of the flow of time in the gravitational field. From Einstein’s equivalence principle, the influence of the Sun and Moon masses on clocks is given in the form of tidal potentials. Two clocks fixed on the surface of the Earth, compared to each other, can measure the tidal effec...

We generalize the combinatorial algebraic approach first proposed by Dhurandhar et al. to construct various classes of modified second-generation time-delay interferometry (TDI) solutions. The main idea behind the original algorithm is to enumerate, in a given order, a specific type of commutator between two monomials defined by the products of par...

Future space gravitational-wave detectors will detect gravitational waves with high sensitivity in the mHz frequency band. One possible source is the stochastic gravitational-wave background (SGWB), possibly from astronomy and cosmology. Detecting SGWB could provide an opportunity to directly examine the polarization of gravitational waves. While g...

Inspired by the combinatorial algebraic approach proposed by Dhurandhar et al., we propose two novel classes of second-generation time-delay interferometry (TDI) solution as well as their further generalization. The primary strategy of the algorithm is to enumerate specific types of residual laser frequency noise associated with second-order commut...

A crucial challenge to the ongoing endeavor of spaceborne gravitational wave (GW) detection resides in the laser phase noise, typically 7 to 8 orders of magnitude above the inevitable noise. The arm-locking technique was proposed to suppress the noise in prestabilized laser beams. Based on the feedback control theory, it is implemented by appropria...

A crucial challenge to the ongoing endeavor of spaceborne gravitational wave (GW) detection resides in the laser phase noise, typically 7 to 8 orders of magnitude above the inevitable noise. The arm locking technique was proposed to suppress the noise in pre-stabilized laser beams. Based on the feedback control theory, it is implemented by appropri...

Recent studies based on the notion of black hole pseudospectrum indicated substantial instability of the fundamental and high-overtone quasinormal modes. Besides its theoretical novelty, the details about the migration of the quasinormal mode spectrum due to specific perturbations may furnish valuable information on the properties of associated gra...

We report a hyperfine-states related weak equivalence principle (WEP) test which searches for possible WEP violation signal in single atom interferometer. With the ground hyperfine states $\left|F=1\right\rangle$ and $\left|F=2\right\rangle$ of $^{87}$Rb atoms simultaneously scanned over different paths in a Raman Mach-Zehnder interferometer (MZI),...

We generalize the combinatorial algebraic approach first proposed by Dhurandhar et al. to construct various classes of modified second-generation time-delay interferometry (TDI) solutions. The main idea behind the algorithm is to enumerate, in a given order, a specific type of commutator between two monomials defined by the products of particular t...

We check the validity of the strong cosmic censorship (SCC) for the massless scalar field on top of a charged black hole in an acceleratingly expanding universe driven by the quintessence fluid with the constant equation of state parameter. As a result, we find that the violation of the SCC occurs as the black hole gets close to the extremal limit....

The search for dynamically screening the coupling between the scalar field and matter in high-density environment is achievable with the symmetron model. The high-accuracy and short-range gravity experiment is proposed to test the symmetron model. In this Letter, the data of the HUST-2020 torsion pendulum experiment testing the inverse-square law a...

While general relativity predicts only two tensor modes for gravitational wave polarization, general metric theories of gravity allows up to four additional modes, including two vector and two scalar modes. Observing the polarization modes of gravitational waves could provide a direct test of the modified gravity. The stochastic gravitational wave...

Atom interferometry provides an important method of high-precision absolute gravity measurement. As absolute gravimeters, various systematic errors of atom gravimeters have been identified and evaluated. Here a comprehensive evaluation of systematic errors for gravity measurements by HUST-QG is presented. HUST-QG exhibited a short-term sensitivity...

Both the fluctuations of the onboard lasers and clocks in a space-based gravitational wave interferometer can significantly decrease the sensitivity of the detector to an unacceptable performance level. Implementing a self-referenced optical frequency comb (OFC) driven by the onboard laser can establish the relationship between these two phase fluc...

Short-range experiment with striped design of the test and source masses offers uniquely sensitive probes for Lorentz Violation. In our previous work, we proposed to combine the horizontally and vertically striped experiments to constrain the violating parameters. Here, we further point out adopting the vertically striped structure with the experim...

A pulsar timing array (PTA) is expected to detect a gravitational wave background (GWB) in the nanohertz band within the next decade. This provides an opportunity for one to test gravity theory and cosmology. A typical data analysis method to detect GWB is cross-correlation analysis. The overlap reduction function (ORF) plays an important role in t...

Time delay interferometry (TDI) is an algorithm proposed to suppress the laser frequency noise in space-borne gravitational-wave detectors. As a post-processing technique, it is implemented by constructing a virtual equal-arm interferometer through an appropriate combination of the time-shifted data streams. Such an approach is tailored to the intr...

In this paper, we study the quasinormal mode and late-time tail of charged massless scalar perturbations of a black hole in the generalized Rastall gravity. The black hole metric in question is spherically symmetric, accompanied by a power-Maxwell field surrounded by a quintessence fluid. It is shown that the massless scalar field, when {\it dresse...

The TianQin Project is aiming at gravitational wave (GW) detection in space. TianQin GW observatory comprises three satellites orbiting on $1 \times 10^5$ km Earth orbits to form an equilateral-triangle constellation. In order to minimize the variations of arm-length and breathing angle, the satellites must be launched and adjusted precisely into a...

The time delay interferometry (TDI) is an algorithm proposed to suppress the laser frequency noise in space-borne gravitational wave detectors. As a post-processing technique, it is implemented by constructing a virtual equal arm interferometer through an appropriate combination of the time-shifted data streams. Such an approach is tailored to the...

Pulsar timing array (PTA) is expected to detect gravitational wave background (GWB) in the nanohertz band within the next decade. This provides an opportunity to test the gravity theory and cosmology. A typical data analysis method to detect GWB is cross-correlation analysis. The overlap reduction function (ORF) plays an important role in the corre...

For the experiments of testing the Newtonian Inverse-Square Law (ISL) at short range, we have analyzed the residual gas damping effect under the assumption of the temperature of the gas is isothermal [Ke J et al 2020 Class. Quantum. Grav. 37 205008]. However, when the test mass squeezes the gas, the temperature of the gas will change accordingly an...

Short-range tests of the gravitational inverse-square law are very important for finding new interactions. In order to further improve the constraints on the Yukawa-like gravitational force, we propose a new scheme based on the torsion balance, where the speculative Yukawa-like gravitational force between the pendulum and the attractor is substanti...

Recent studies based on the notion of black hole pseudospectrum indicated substantial instability of the fundamental and high-overtone quasinormal modes. Besides its theoretical novelty, the details about the migration of the quasinormal mode spectrum due to specific perturbations may furnish valuable information on the properties of associated gra...

Cuspy shadow was first reported for hairy rotating black holes, whose metrics deviate significantly from the Kerr one. The non-smooth edge of the shadow is attributed to a transition between different branches of unstable but bounded orbits, known as the fundamental photon orbits, which end up at the light rings. In searching for a minimal theoreti...

The ongoing development of the space-based laser interferometer missions is aiming at unprecedented gravitational wave detections in the millihertz frequency band. The spaceborne nature of the experimental setups leads to a degree of subtlety regarding the otherwise overwhelming laser frequency noise. The cancellation of the latter is accomplished...

In this work, we describe an updated version of single arm locking, and the noise amplification due to the nulls can be flexibly restricted with the help of optical frequency comb. We show that, the laser phase noise can be divided by a specific factor with optical frequency comb as the bridge. The analytical results indicate that, the peaks in the...

The Newtonian gravitational constant G has proved to be one of the most difficult constants to measure in physics. The improvement of measuring G with the atomic interferometry method is significantly limited by the positioning accuracy of the atom clouds and source masses, and the measurement accuracy of the atomic velocity. In this article, we pr...

The atom interferometry is a promising tool for the detection of the gravitational wave (GW) in the mid-frequency band ranging from 0.01 Hz to 10 Hz. Particularly, the multi-arm atom interference detectors can help to extract better data with the removal of fake detection. The existing models for GW detection with atom interferometry, however, are...

Direct observation of gravitational waves offers us numerous novel possibilities to further explore the Universe. In practice, the efficiency of the experimental facility for a given gravitational wave source can be measured in terms of the sensitivity function of the instrument. The latter essentially indicates the least incident amplitude require...

The ongoing development of the space-based laser interferometer missions is aiming at unprecedented gravitational wave detections in the millihertz frequency band. The spaceborne nature of the experimental setups leads to a degree of subtlety regarding the otherwise overwhelming laser frequency noise. The cancellation of the latter is accomplished...

Experiments measuring the Newtonian gravitational constant G can offer uniquely sensitive probes of the test of the gravitational inverse-square law. An analysis of the non-Newtonian effect in two independent experiments measuring G is presented, which permits a test of the 1/r2 law at the centimeter range. This work establishes the strongest bound...

The chameleon model was proposed as a promising candidate for the dark energy screening mechanism. It is not straightforward to detect the fifth force mediated by the chameleon scalar field in a high-density environment, such as those in a ground-based laboratory. Nevertheless, short-range gravitational experiments such as the torsion pendulum expe...

The principal aim of the space-based gravitational wave detectors is to explore the gravitational waves in the 0.1 mHz-1 Hz frequency band. To maximize the potential capability of the experimental apparatus regarding the instrument performance, one needs to acquire accurate information on its sensitivity limit. The sensitivity curve in question, by...

Improving the precision of current tests of the equivalence principle with a rotating torsion pendulum requires a more complete analysis of systematic effects. Here, we discuss in detail one of the important systematic effects, the influence from the tilt error motion of the rotation axis of a rotary stage, namely, wandering of the instantaneous ro...

Cuspy shadow was first reported for hairy rotating black holes, whose metrics deviate significantly from the Kerr one. The non-smooth edge of the shadow is attributed to a transition between different branches of unstable but bounded orbits, known as the fundamental photon orbits, which end up at the light rings. In searching for a minimal theoreti...

Many theories, such as the unification theories that would include gravitation, predict deviations from Newtonian inverse-square law (ISL) at short range. Many high precision experiments have been performed, but additional experiments are still of high scientific importance. Here, we discuss the torque thermal noise caused by residual gas damping,...

The Newtonian gravitational constant G, which is one of the most important fundamental physical constants in nature, plays a significant role in the fields of the theoretical physics, geophysics, astrophysics, and astronomy. Although G was the first physical constant to be introduced in the history of science, it is considered to be one of the most...

Given the high-precision modern space mission, a precise relativistic modeling of observations is required. By solving the eikonal equation with the post-Newtonian approximation, the light propagation is determined by the iterative method in the gravitational field of an isolated, gravitationally bound N-body system. Different from the traditional...

Time-delay interferometry is put forward to improve the signal-to-noise ratio of space-borne gravitational wave detectors by canceling the large laser phase noise with different combinations of measured data. Based on the Michelson data combination, the sensitivity function of the detector can be obtained by averaging the all-sky wave source positi...

We consider the relativistic tidal effects on frequency shift of clock-comparison experiments. The relativistic formulation for frequency shift and time transfer is derived in the gravitational field of a tidal, axisymmetric, and rotating Earth. With the help of Love numbers describing the tidal response of solid Earth, we formulize the mathematica...

In this paper, we study the quasinormal modes of the massless Dirac field for charged black holes in Rastall gravity. The spherically symmetric black hole solutions in question are characterized by the presence of a power-Maxwell field, surrounded by the quintessence fluid. The calculations are carried out by employing the WKB approximations up to...

We construct a quasi-inertial reference system for the atom interferometer in terms of the light-field compensation, which is equivalent to the establishment of a quantum drag-free system. The compensation considered in our approach involves feedbacks of both classical and quantum nature. As a result, it may significantly reduce the dependence of t...

Since the double-loop atom interferometer consisting of Raman π2−π−π−π2 four-pulse sequences can eliminate the dependence of the interferometric phase shift on the atomic initial velocity, it is widely used for rotation measurements. However, our research shows that by coupling itself with both the atomic initial velocity and the laser detuning, th...

In the recent CODATA-2014 adjustment, the G values obtained by different groups are not in good agreement with each other within respective uncertainties, which may be attributed to the possible unknown or incorrectly evaluated systematic errors in different methods. This paper proposes a scheme to measure G with two independent methods. The first...