We study the lensing phenomena of the strong gravity regime of five-dimensional charged,equally rotating black holes with a cosmological constant,familiarly known as the Cvetic–Lu–Pope(CLP)black holes.These black ho...We study the lensing phenomena of the strong gravity regime of five-dimensional charged,equally rotating black holes with a cosmological constant,familiarly known as the Cvetic–Lu–Pope(CLP)black holes.These black holes are characterized by three observable parameters,the mass M,the charge Q and the angular momentum J,in addition to the cosmological constant.We investigate the strong gravitational lensing observables,mainly the photon sphere radius,the minimum impact parameter,the deflection angle,the angular size,and the magnification of the relativistic images.We model the M87 and SgrA*for these observables.We also focus on the relativistic time delay effect in the strong-field regime of gravity and the impact of the observable on it.The analytical expressions for the observables of the relativistic images with vanishing angular momentum(j=0)are discussed in some detail.We shed a light on the gravitational time delay effect by incorporating the lensing observables.The gravitational time delay has a direct consequence on the photon sphere radius and hence on the quasinormal modes.展开更多
When a planet is ejected from its star-planet system due to dynamical interactions,its satellite may remain gravitationally bound to the planet.The Chinese Space Station Telescope(CSST)will be capable of detecting a l...When a planet is ejected from its star-planet system due to dynamical interactions,its satellite may remain gravitationally bound to the planet.The Chinese Space Station Telescope(CSST)will be capable of detecting a large number of low-mass free-floating planet events(FFPs)from a bulge microlensing survey.We assess the feasibility of detecting satellites(a.k.a.,exomoons)orbiting FFPs by simulating CSST light curves and calculating the detection efficiency as a function of satellite-to-planet mass ratios(q)and projected separations(s)in units of the Einstein radius.For a Neptune-class FFP in the Galactic disk with a Sun-like star as the microlensed source,CSST can detect Earth-mass satellites over a decade of separations(∼0.01-0.1 au)and has sensitivity down to Moon-mass satellites(q∼10^(−3))at s^(∼1).CSST also has some sensitivity to detect Moon-mass satellites at s∼2(∼0.02 au)orbiting an Earth-mass FFP in the disk.CSST has substantially reduced sensitivity for detecting satellites when the source star is an M dwarf,compared to a Sun-like source.We also calculate the satellite detection efficiency for the dedicated microlensing survey of the Roman Space Telescope(Roman),which demonstrates greater sensitivity than CSST,particularly for M-dwarf sources.Notably,some of the Neptune-Earth systems detectable by CSST and Roman may exhibit significant tidal heating.展开更多
In this paper,we investigate the optical properties of a non-rotating charged black hole(BH)in the Einstein-Maxwell-scalar(EMS)theory,together with a plasma medium.We first consider the photon sphere and shadow radius...In this paper,we investigate the optical properties of a non-rotating charged black hole(BH)in the Einstein-Maxwell-scalar(EMS)theory,together with a plasma medium.We first consider the photon sphere and shadow radius under the impact of the plasma medium existing in the environment surrounding the BH in the EMS theory.We show that the radius of the photon sphere and the BH shadow decrease under the influence of the parameterβ.We further study gravitational weak lensing in detail by adapting general methods and derive the light ray's deflection angle around the BH together with the plasma environment.It is found that for uniform plasma,the deflection angle increases with the rise of the plasma parameter,whereas it decreases with the increase of the plasma parameter for non-uniform plasma.Besides,we also study the magnification of image brightness.展开更多
We investigate the impact of the modified gravity(MOG)field and the quintessence scalar field on horizon evolution,black hole(BH)shadow and the weak gravitational lensing around a static spherically symmetric BH.We fi...We investigate the impact of the modified gravity(MOG)field and the quintessence scalar field on horizon evolution,black hole(BH)shadow and the weak gravitational lensing around a static spherically symmetric BH.We first begin to write the BH metric associated with the MOG parameter and quintessence scalar field.We then determine the BH shadow and obtain numerical solutions for the photon sphere and shadow radius.We show that the MOG(α)and the quintessence(c)parameters have a significant impact on the BH shadow and photon sphere.Based on the analysis,we further show that the combined effects of the MOG parameter and quintessence field can increase the values of BH shadow and photon sphere radii.We also obtain constraints on the BH parameters by applying the observational data of Sgr A^(★)and M87^(★).Finally,we consider the weak deflection angle of BH within the context of the Gauss-Bonnet theorem(GBT)and show that the combined effects of the MOG and quintessence parameters do make the value of the deflection angle increase,and find this remarkable property is in good agreement with the physical meaning of both parameters that can maintain the strong gravitational field in the surrounding environment of a BH.展开更多
In this study,we examine the effects of weak gravitational lensing and determine the shadow radius around black holes within the Dyonic ModMax(DM)spacetime,also accounting for models with nonuniform plasma distributio...In this study,we examine the effects of weak gravitational lensing and determine the shadow radius around black holes within the Dyonic ModMax(DM)spacetime,also accounting for models with nonuniform plasma distributions.By analyzing various gravitational lens models,we compare corrections to vacuum lensing due to gravitational effects within plasma and plasma inhomogeneity,finding that these effects could be observed in hot gas within galaxy clusters.Starting with the orbits of photons around a black hole in DM,we investigate the shadow and weak gravitational lensing phenomena.Utilizing observational data from the Event Horizon Telescope for M87*and SgrA*,we constrain parameters within DM gravity.To connect our findings to observations,we examine the magnification and positioning of lensed images,along with the weak deflection angle and magnification for sources near different galaxies.展开更多
The principal testing ground for general relativity is the observable Universe. Gravitational lensing is the leading observational technique that gives insight into the distribution of baryonic matter in the stellar, ...The principal testing ground for general relativity is the observable Universe. Gravitational lensing is the leading observational technique that gives insight into the distribution of baryonic matter in the stellar, galactic and cosmological scale, as well as the distribution of dark matter and dark energy, due to their gravitational interaction. Interpretation of ever more precise observational data requires increasingly subtle analytical techniques. In this paper, I discuss a formalism that can handle a nonlinear superposition of gravitational and refractive lensing by a grouping of baryonic matter, dark matter and dark energy for a given distribution of those entities (i.e. for a given spacetime metric) and their refractive properties. The role of refraction in gravitational lensing is exemplified in the case of a microlensing event and a signature of such an effect is discussed.展开更多
The effects of the gravitational redshift of gravitons upon spiral galaxy rotation energy are compared to the standard mass to light analyses in obtaining rotation curves. The derivation of the total baryonic matter c...The effects of the gravitational redshift of gravitons upon spiral galaxy rotation energy are compared to the standard mass to light analyses in obtaining rotation curves. The derivation of the total baryonic matter compares well with the standard theory and the rotation velocity is matched to a high precision. The stellar mass distributions obtained from the fit with graviton energy loss are used to derive the surface brightness magnitudes for the galaxies, which agree well with the observed measurements. In a new field of investigation, the graviton theory is applied to the observations of gravitational lenses. The results of these applications of the theory suggest that it can augment the standard methods and may eliminate the need for dark matter.展开更多
We report the discovery of 4 strong gravitational lensing systems by visual inspections of the Sloan Digital Sky Survey images of galaxy clusters in Data Release 6 （SDSS DR6）. Two of the four systems show Einstein r...We report the discovery of 4 strong gravitational lensing systems by visual inspections of the Sloan Digital Sky Survey images of galaxy clusters in Data Release 6 （SDSS DR6）. Two of the four systems show Einstein rings while the others show tangen- tial giant arcs. These arcs or rings have large angular separations （〉 8″） from the bright central galaxies and show bluer color compared with the red cluster galaxies. In addition, we found 5 probable and 4 possible lenses by galaxy clusters.展开更多
We investigate the formation of multiple images as the radio signals from fast radio bursts(FRBs)pass through the plane of a plasma clump.The exponential model for the plasma clump is adopted to analyze the properties...We investigate the formation of multiple images as the radio signals from fast radio bursts(FRBs)pass through the plane of a plasma clump.The exponential model for the plasma clump is adopted to analyze the properties of the multiple images.By comparing with the classical dispersion relations,we find that one image has exhibited specific inverse properties to others,such as their delay times at high frequency is higher than that at low frequency,owing to the lensing effects of the plasma clump.We demonstrate that these inverse effects should be observable in some repeating FRBs.Our results predict deviation in the estimated dispersion measure(DM)across multiple images,consistent with the observations of FRB 121102 and FRB 180916.J0158+65.If other plasma lenses have effects similar to an exponential lens,we find that they should also give rise to a similar dispersion relation in the multiple images.For some repeating FRBs,analysis of the differences in time delay and in DM between multiple images at different frequencies can serve as a method to reveal the plasma distribution.展开更多
We identify new strong lensing clusters of galaxies from the Sloan Digital Sky Survey Ⅲ （SDSS DR8） by visually inspecting color images of a large sample of clusters of galaxies. We find 68 new clusters showing gian...We identify new strong lensing clusters of galaxies from the Sloan Digital Sky Survey Ⅲ （SDSS DR8） by visually inspecting color images of a large sample of clusters of galaxies. We find 68 new clusters showing giant arcs in addition to 30 known lensing systems. Among 68 cases, 13 clusters are ＂almost certain＂ lensing systems with tangential giant arcs, 22 clusters are ＂probable＂ and 31 clusters are ＂pos- sible＂ lensing systems. We also find two exotic systems with blue rings. The giant arcs have angular separations of 2.0jj - 25.7j~ from the bright central galaxies. We note that the rich clusters are more likely to be lensing systems and the separations between the arcs and the central galaxies increase with cluster richness.展开更多
Strong lensing is one of the most spectacular views in the universe.Many cosmological applications have been proposed,but the number of such lensing systems is still limited.In this work,we applied an improved version...Strong lensing is one of the most spectacular views in the universe.Many cosmological applications have been proposed,but the number of such lensing systems is still limited.In this work,we applied an improved version of a previously developed spectroscopic lensing search method to the SDSS-Ⅲ BOSS and proposed a list of highly possible candidates.Follow-up CFHT Megacam imaging observations were performed for five systems,and two out of five are probably strong lensing systems with at least one image close to the central galaxy,although no counter images are detected.展开更多
The discovery by the author of real magnetic charges and true anti-electrons in the atomic structures allowed him to establish that the gravitational field (GF) in reality is the vortex electromagnetic field. Dependin...The discovery by the author of real magnetic charges and true anti-electrons in the atomic structures allowed him to establish that the gravitational field (GF) in reality is the vortex electromagnetic field. Depending on the vector conditions the gravitational fields can be either paragravitational (PGF) or ferrogravitational (FGF). Masses (atoms, nucleons, etc.) emitting PGF manifest so-called attraction to each other. In fact, this process is the pressing of atoms or nucleons to each other by the forces of gravitational “Dark energy”. Namely the gravitational “Dark energy” which is formed between the masses emitting PGF and compressing of nucleons in atomic nuclei is the main force factor determining the formation of nuclear forces. Masses that emit FGF are repelled from PGF sources, for example, from the Earth. The last gravitational manifestation, discovered by the author, this is of the effect of the gravitational levitation. The atomic shell and atomic nucleus are autonomous sources of gravitational field in atomic compositions. The gravitational fields emitted these sources, by its physical parameters, are different gravitational fields, what associated with differences in the magnitudes charges of magnetic and electric particles in their compositions. The noted differences in the parameters of the GF are of reason that in atoms the process of extrusion of foreign gravitational field from the region of given gravitational source is realized. This effect should be called the effect of intra-atomic gravitational shielding (IAGS). Within the framework of this effect the shell of the atom is a kind of gravitational “insulator” that prevents the PGF of the nucleons from leaving beyond of the atom. As result of the IAGS effect, the concentration PGF of nucleons is realized only in the region of the nucleus, which leads to an increase in nuclear forces. However, the resistance of the marked “insulator” is finite and if the critical voltage PGF on the nucleus is exceeded, the complete shielding of the nucleon fields by the atomic shell is broken. As result of the leakage of a part of the PGF of nucleons beyond the atom, the density of this field in the region of the nucleus decreases significantly, which leads to a weakening of the nuclear forces and often leads to radioactivity. The effect of gravitational shielding is directly related to such a well-known concept as the mass defect of the nucleus. It is the exclusion of the gravitational field formed by the nucleons in the composition of the atomic nucleus as a result of the full IAGS effect that creates the illusion of atomic mass defect.展开更多
Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse application...Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications. The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights. （1） Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects （MACHOs）. This confirms most dark matter is non-baryonic, consistent with other observations. （2） Microlensing has discovered about 20 extrasolar planets （16 published）, including the first two Jupiter-Saturn like systems and the only five ＂cold Neptunes＂ yet de- tected. They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation. （3） Microlensing pro- vides a unique way to measure the mass of isolated stars, including brown dwarfs and normal stars. Half a dozen or so stellar mass black hole candidates have also been pro- posed. （4） High-resolution, target-of-opportunity spectra of highly-magnified dwarf stars provide intriguing ＂age＂ determinations which may either hint at enhanced he- lium enrichment or unusual bulge formation theories. （5） Microlensing also measured limb-darkening profiles for close to ten giant stars, which challenges stellar atmo- sphere models. （6） Data from surveys also provide strong constraints on the geometry and kinematics of the Milky Way bar （through proper motions）; the latter indicates predictions from current models appear to be too anisotropic compared with observa- tions. The future of microlensing is bright given the new capabilities of current surveys and forthcoming new telescope networks from the ground and from space. Some open issues in the field are identified and briefly discussed.展开更多
We study the cosmic constraint to the wCDM （cold dark matter with a constant equation of state w） model via 118 strong gravitational lensing systems which are compiled from SLA CS, BELLS, LSD and SL2S surveys, where...We study the cosmic constraint to the wCDM （cold dark matter with a constant equation of state w） model via 118 strong gravitational lensing systems which are compiled from SLA CS, BELLS, LSD and SL2S surveys, where the ratio between two angular diameter distances Dobs =DA（Zl, Zs ） / D A （ O, Zs ） is taken as a cosmic observable. To obtain this ratio, we adopt two strong tensing models： one is the singular isothermal sphere model （SIS） and the other one is the power-law density profile （PLP） model. Via the Markov chain Monte Carlo method, the posterior distribution of the cosmological model parameters space is obtained. The results show that the cosmological model parameters are not sensitive to the parameterized forms of the power-law index γ. Furthermore, the PLP model gives a relatively tighter constraint to the cosmological parameters than that of the SIS model. The predicted value of Ωm = 0.31＋0.44 -0.24 by the SIS model is compatible with that obtained by P1anck2015： Ωm = 0.313 ± 0.013. However, the value of Ωm =0.15＋0.13 -0.11 based on the PLP model is smaller and has 1.25σ tension with that obtained by Planck2015.展开更多
Theoretical investigations into the deflection angle caused by microlenses offer a direct path to uncovering principles of the cosmological microlensing effect.This work specifically concentrates on the the probabilit...Theoretical investigations into the deflection angle caused by microlenses offer a direct path to uncovering principles of the cosmological microlensing effect.This work specifically concentrates on the the probability density function(PDF)of the light deflection angle induced by microlenses.We have made several significant improvements to the widely used formula from Katz et al.First,we update the coefficient from 3.05 to 1.454,resulting in a better fit between the theoretical PDF and our simulation results.Second,we developed an elegant fitting formula for the PDF that can replace its integral representation within a certain accuracy,which is numerically divergent unless arbitrary upper limits are chosen.Third,to facilitate further theoretical work in this area,we have identified a more suitable Gaussian approximation for the fitting formula.展开更多
The error propagation among estimated parameters reflects the correlation among the parameters.We study the capability of machine learning of"learning"the correlation of estimated parameters.We show that mac...The error propagation among estimated parameters reflects the correlation among the parameters.We study the capability of machine learning of"learning"the correlation of estimated parameters.We show that machine learning can recover the relation between the uncertainties of different parameters,especially,as predicted by the error propagation formula.Gravitational lensing can be used to probe both astrophysics and cosmology.As a practical application,we show that the machine learning is able to intelligently find the error propagation among the gravitational lens parameters(effective lens mass ML and Einstein radiusθ_(E))in accordance with the theoretical formula for the singular isothermal ellipse(SIE)lens model.The relation of errors of lens mass and Einstein radius,(e.g.,the ratio of standard deviations F=σ_(ML)/σ_(θ_(E)))predicted by the deep convolution neural network are consistent with the error propagation formula of the SIE lens model.As a proof-of-principle test,a toy model of linear relation with Gaussian noise is presented.We found that the predictions obtained by machine learning indeed indicate the information about the law of error propagation and the distribution of noise.Error propagation plays a crucial role in identifying the physical relation among parameters,rather than a coincidence relation,therefore we anticipate our case study on the error propagation of machine learning predictions could extend to other physical systems on searching the correlation among parameters.展开更多
We study the particle dynamics around a black hole(BH)in f(Q)gravity.First,we investigate the influence of the parameters of f(Q)gravity on the horizon structure of the BH,photon orbits and the radius of the innermost...We study the particle dynamics around a black hole(BH)in f(Q)gravity.First,we investigate the influence of the parameters of f(Q)gravity on the horizon structure of the BH,photon orbits and the radius of the innermost stable circular orbit(ISCO)of massive particles.We further study the effects of the parameters of f(Q)gravity on the shadow cast by the BH.Moreover,we consider weak gravitational lensing using the general method,where we also explore the deflection angle of light rays around the BH in f(Q)gravity in uniform and nonuniform plasma mediums.展开更多
Weak gravitational lensing is a powerful tool in modern cosmology.To accurately measure the weak lensing signal,one has to control the systematic bias on a small level.One of the most difficult problems is how to corr...Weak gravitational lensing is a powerful tool in modern cosmology.To accurately measure the weak lensing signal,one has to control the systematic bias on a small level.One of the most difficult problems is how to correct the smearing effect of the Point-Spread Function(PSF)on the shape of the galaxies.The chromaticity of PSF for a broad-band observation can lead to new subtle effects.Since the PSF is wavelength-dependent and the spectrum energy distributions between stars and galaxies are different,the effective PSF measured from the star images will be different from those that smear the galaxies.Such a bias is called color bias.We estimate it in the optical bands of the Chinese Space Station Survey Telescope from simulated PSFs,and show the dependence on the color and redshift of the galaxies.Moreover,due to the spatial variation of spectra over the galaxy image,another higher-order bias exists:color gradient bias.Our results show that both color bias and color gradient bias are generally below 0.1%in CSST.Only for small-size galaxies,one needs to be careful about the color gradient bias in the weak lensing analysis using CSST data.展开更多
Cosmological numerical simulations of galaxy formation have led to the cuspy density profile of a pure cold dark matter halo toward the center, which is in sharp contradiction with the observations of the rotation cur...Cosmological numerical simulations of galaxy formation have led to the cuspy density profile of a pure cold dark matter halo toward the center, which is in sharp contradiction with the observations of the rotation curves of cold dark matter-dominated dwarf and low surface brightness disk galaxies, with the latter tending to favor mass profiles with a flat central core. Many efforts have been devoted to resolving this cusp-core problem in recent years, among them, baryon-cold dark matter interactions are considered to be the main physical mechanisms erasing the cold dark matter （CDM） cusp into a flat core in the centers of all CDM halos. Clearly, baryon-cold dark matter interactions are not customized only for CDM-dominated disk galaxies, but for all types, including giant ellipticals. We first fit the most recent high resolution observations of rotation curves with the Burkert profile, then use the constrained core size-halo mass relation to calculate the lensing frequency, and compare the predicted results with strong lensing observations. Unfortunately, it turns out that the core size constrained from rotation curves of disk galaxies cannot be extrapolated to giant ellipticals. We conclude that, in the standard cosmological paradigm, baryon-cold dark matter interactions are not universal mechanisms for galaxy formation, and therefore, they cannot be true solutions to the cusp-core problem.展开更多
A class of braneworld black holes, which I called as Bronnikov–Melnikov–Dehen(BMD) black holes,are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate...A class of braneworld black holes, which I called as Bronnikov–Melnikov–Dehen(BMD) black holes,are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate the angular positions and magnifications of relativistic images as well as the time delay between different relativistic images. I also compare the results with those obtained for Schwarzschild and two braneworld black holes, i.e., the tidal Reissner-Nordstr¨om(R-N) and the Casadio–Fabbri–Mazzacurati(CFM) black holes.展开更多
基金supported by the National Natural Science Foundation of China under Grants Nos.12475056,12347177,and 12247101,the 111 Project under Grant No.B20063Lanzhou City's scientific research funding subsidy to Lanzhou Universitythe Gansu Province Major Scientific and Technological Special Project。
文摘We study the lensing phenomena of the strong gravity regime of five-dimensional charged,equally rotating black holes with a cosmological constant,familiarly known as the Cvetic–Lu–Pope(CLP)black holes.These black holes are characterized by three observable parameters,the mass M,the charge Q and the angular momentum J,in addition to the cosmological constant.We investigate the strong gravitational lensing observables,mainly the photon sphere radius,the minimum impact parameter,the deflection angle,the angular size,and the magnification of the relativistic images.We model the M87 and SgrA*for these observables.We also focus on the relativistic time delay effect in the strong-field regime of gravity and the impact of the observable on it.The analytical expressions for the observables of the relativistic images with vanishing angular momentum(j=0)are discussed in some detail.We shed a light on the gravitational time delay effect by incorporating the lensing observables.The gravitational time delay has a direct consequence on the photon sphere radius and hence on the quasinormal modes.
基金supported by the National Natural Science Foundation of China(grant No.12133005)the China Manned Space Program with grant No.CMS-CSST-2025-A16.S.D.acknowledges the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘When a planet is ejected from its star-planet system due to dynamical interactions,its satellite may remain gravitationally bound to the planet.The Chinese Space Station Telescope(CSST)will be capable of detecting a large number of low-mass free-floating planet events(FFPs)from a bulge microlensing survey.We assess the feasibility of detecting satellites(a.k.a.,exomoons)orbiting FFPs by simulating CSST light curves and calculating the detection efficiency as a function of satellite-to-planet mass ratios(q)and projected separations(s)in units of the Einstein radius.For a Neptune-class FFP in the Galactic disk with a Sun-like star as the microlensed source,CSST can detect Earth-mass satellites over a decade of separations(∼0.01-0.1 au)and has sensitivity down to Moon-mass satellites(q∼10^(−3))at s^(∼1).CSST also has some sensitivity to detect Moon-mass satellites at s∼2(∼0.02 au)orbiting an Earth-mass FFP in the disk.CSST has substantially reduced sensitivity for detecting satellites when the source star is an M dwarf,compared to a Sun-like source.We also calculate the satellite detection efficiency for the dedicated microlensing survey of the Roman Space Telescope(Roman),which demonstrates greater sensitivity than CSST,particularly for M-dwarf sources.Notably,some of the Neptune-Earth systems detectable by CSST and Roman may exhibit significant tidal heating.
基金supported by the National Natural Science Foundation of China under Grant No.11675143the National Key Research and Development Program of China under Grant No.2020YFC2201503。
文摘In this paper,we investigate the optical properties of a non-rotating charged black hole(BH)in the Einstein-Maxwell-scalar(EMS)theory,together with a plasma medium.We first consider the photon sphere and shadow radius under the impact of the plasma medium existing in the environment surrounding the BH in the EMS theory.We show that the radius of the photon sphere and the BH shadow decrease under the influence of the parameterβ.We further study gravitational weak lensing in detail by adapting general methods and derive the light ray's deflection angle around the BH together with the plasma environment.It is found that for uniform plasma,the deflection angle increases with the rise of the plasma parameter,whereas it decreases with the increase of the plasma parameter for non-uniform plasma.Besides,we also study the magnification of image brightness.
基金supported by the National Natural Science Foundation of China under Grant No. 11675143the National Key Research and Development Program of China under Grant No. 2020YFC2201503the support from Research Grant F-FA-2021-432 of the Ministry of Higher Education, Science and Innovations of the Republic of Uzbekistan。
文摘We investigate the impact of the modified gravity(MOG)field and the quintessence scalar field on horizon evolution,black hole(BH)shadow and the weak gravitational lensing around a static spherically symmetric BH.We first begin to write the BH metric associated with the MOG parameter and quintessence scalar field.We then determine the BH shadow and obtain numerical solutions for the photon sphere and shadow radius.We show that the MOG(α)and the quintessence(c)parameters have a significant impact on the BH shadow and photon sphere.Based on the analysis,we further show that the combined effects of the MOG parameter and quintessence field can increase the values of BH shadow and photon sphere radii.We also obtain constraints on the BH parameters by applying the observational data of Sgr A^(★)and M87^(★).Finally,we consider the weak deflection angle of BH within the context of the Gauss-Bonnet theorem(GBT)and show that the combined effects of the MOG and quintessence parameters do make the value of the deflection angle increase,and find this remarkable property is in good agreement with the physical meaning of both parameters that can maintain the strong gravitational field in the surrounding environment of a BH.
基金partly supported by Research Grants FZ-20200929344 and F-FA-2021-510 of the Uzbekistan Ministry for Innovative DevelopmentTUBITAKSCOAP3 for their support。
文摘In this study,we examine the effects of weak gravitational lensing and determine the shadow radius around black holes within the Dyonic ModMax(DM)spacetime,also accounting for models with nonuniform plasma distributions.By analyzing various gravitational lens models,we compare corrections to vacuum lensing due to gravitational effects within plasma and plasma inhomogeneity,finding that these effects could be observed in hot gas within galaxy clusters.Starting with the orbits of photons around a black hole in DM,we investigate the shadow and weak gravitational lensing phenomena.Utilizing observational data from the Event Horizon Telescope for M87*and SgrA*,we constrain parameters within DM gravity.To connect our findings to observations,we examine the magnification and positioning of lensed images,along with the weak deflection angle and magnification for sources near different galaxies.
文摘The principal testing ground for general relativity is the observable Universe. Gravitational lensing is the leading observational technique that gives insight into the distribution of baryonic matter in the stellar, galactic and cosmological scale, as well as the distribution of dark matter and dark energy, due to their gravitational interaction. Interpretation of ever more precise observational data requires increasingly subtle analytical techniques. In this paper, I discuss a formalism that can handle a nonlinear superposition of gravitational and refractive lensing by a grouping of baryonic matter, dark matter and dark energy for a given distribution of those entities (i.e. for a given spacetime metric) and their refractive properties. The role of refraction in gravitational lensing is exemplified in the case of a microlensing event and a signature of such an effect is discussed.
文摘The effects of the gravitational redshift of gravitons upon spiral galaxy rotation energy are compared to the standard mass to light analyses in obtaining rotation curves. The derivation of the total baryonic matter compares well with the standard theory and the rotation velocity is matched to a high precision. The stellar mass distributions obtained from the fit with graviton energy loss are used to derive the surface brightness magnitudes for the galaxies, which agree well with the observed measurements. In a new field of investigation, the graviton theory is applied to the observations of gravitational lenses. The results of these applications of the theory suggest that it can augment the standard methods and may eliminate the need for dark matter.
基金supported by the National Natural Science Foundation of China (NSFC, Nos.10521001, 10773016 and 10833003)the National KeyBasic Research Science Foundation of China (2007CB815403).
文摘We report the discovery of 4 strong gravitational lensing systems by visual inspections of the Sloan Digital Sky Survey images of galaxy clusters in Data Release 6 （SDSS DR6）. Two of the four systems show Einstein rings while the others show tangen- tial giant arcs. These arcs or rings have large angular separations （〉 8″） from the bright central galaxies and show bluer color compared with the red cluster galaxies. In addition, we found 5 probable and 4 possible lenses by galaxy clusters.
基金supported by the National Natural Science Foundation of China(grant Nos.12041304,11873080 and 12033001)supported by the 2021 project Xinjiang Uygur Autonomous Region of China for Tianshan elites,and the National SKA Program of China(grant Nos.U1838109,2020SKA0120100 and 12041301)+4 种基金supported by the Key Laboratory of Xinjiang Uygur Autonomous Region No.2020D04049the National SKA Program of China No.2020SKA0120200the 2018 Project of Xinjiang Uygur Autonomous Region of China for Flexibly Fetching in Upscale Talentssupported by CAS“Light of West China”Program No.2018-XBQNXZ-B-025partly supported by the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administrated by the CAS。
文摘We investigate the formation of multiple images as the radio signals from fast radio bursts(FRBs)pass through the plane of a plasma clump.The exponential model for the plasma clump is adopted to analyze the properties of the multiple images.By comparing with the classical dispersion relations,we find that one image has exhibited specific inverse properties to others,such as their delay times at high frequency is higher than that at low frequency,owing to the lensing effects of the plasma clump.We demonstrate that these inverse effects should be observable in some repeating FRBs.Our results predict deviation in the estimated dispersion measure(DM)across multiple images,consistent with the observations of FRB 121102 and FRB 180916.J0158+65.If other plasma lenses have effects similar to an exponential lens,we find that they should also give rise to a similar dispersion relation in the multiple images.For some repeating FRBs,analysis of the differences in time delay and in DM between multiple images at different frequencies can serve as a method to reveal the plasma distribution.
基金Supported by the National Natural Science Foundation of China(Grant Nos. 10821061, 10833003 and 11103032)Young Researcher Grant of National Astronomical Observatories, Chinese Academy of Sciences and the National Key Basic Research Science Foundation of China (2007CB815403)Funding for SDSS-III has been provided by the Alfred P.Sloan Foundation,the Participating Institutions,the National Science Foundation and the U.S.Department of Energy
文摘We identify new strong lensing clusters of galaxies from the Sloan Digital Sky Survey Ⅲ （SDSS DR8） by visually inspecting color images of a large sample of clusters of galaxies. We find 68 new clusters showing giant arcs in addition to 30 known lensing systems. Among 68 cases, 13 clusters are ＂almost certain＂ lensing systems with tangential giant arcs, 22 clusters are ＂probable＂ and 31 clusters are ＂pos- sible＂ lensing systems. We also find two exotic systems with blue rings. The giant arcs have angular separations of 2.0jj - 25.7j~ from the bright central galaxies. We note that the rich clusters are more likely to be lensing systems and the separations between the arcs and the central galaxies increase with cluster richness.
基金partly supported by the National Key Basic Research and Development Program of China(No.2018YFA0404501 to SM)the National Natural Science Foundation of China(Grant Nos.11821303 and 11761131004 to SM)
文摘Strong lensing is one of the most spectacular views in the universe.Many cosmological applications have been proposed,but the number of such lensing systems is still limited.In this work,we applied an improved version of a previously developed spectroscopic lensing search method to the SDSS-Ⅲ BOSS and proposed a list of highly possible candidates.Follow-up CFHT Megacam imaging observations were performed for five systems,and two out of five are probably strong lensing systems with at least one image close to the central galaxy,although no counter images are detected.
文摘The discovery by the author of real magnetic charges and true anti-electrons in the atomic structures allowed him to establish that the gravitational field (GF) in reality is the vortex electromagnetic field. Depending on the vector conditions the gravitational fields can be either paragravitational (PGF) or ferrogravitational (FGF). Masses (atoms, nucleons, etc.) emitting PGF manifest so-called attraction to each other. In fact, this process is the pressing of atoms or nucleons to each other by the forces of gravitational “Dark energy”. Namely the gravitational “Dark energy” which is formed between the masses emitting PGF and compressing of nucleons in atomic nuclei is the main force factor determining the formation of nuclear forces. Masses that emit FGF are repelled from PGF sources, for example, from the Earth. The last gravitational manifestation, discovered by the author, this is of the effect of the gravitational levitation. The atomic shell and atomic nucleus are autonomous sources of gravitational field in atomic compositions. The gravitational fields emitted these sources, by its physical parameters, are different gravitational fields, what associated with differences in the magnitudes charges of magnetic and electric particles in their compositions. The noted differences in the parameters of the GF are of reason that in atoms the process of extrusion of foreign gravitational field from the region of given gravitational source is realized. This effect should be called the effect of intra-atomic gravitational shielding (IAGS). Within the framework of this effect the shell of the atom is a kind of gravitational “insulator” that prevents the PGF of the nucleons from leaving beyond of the atom. As result of the IAGS effect, the concentration PGF of nucleons is realized only in the region of the nucleus, which leads to an increase in nuclear forces. However, the resistance of the marked “insulator” is finite and if the critical voltage PGF on the nucleus is exceeded, the complete shielding of the nucleon fields by the atomic shell is broken. As result of the leakage of a part of the PGF of nucleons beyond the atom, the density of this field in the region of the nucleus decreases significantly, which leads to a weakening of the nuclear forces and often leads to radioactivity. The effect of gravitational shielding is directly related to such a well-known concept as the mass defect of the nucleus. It is the exclusion of the gravitational field formed by the nucleons in the composition of the atomic nucleus as a result of the full IAGS effect that creates the illusion of atomic mass defect.
文摘Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications. The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights. （1） Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects （MACHOs）. This confirms most dark matter is non-baryonic, consistent with other observations. （2） Microlensing has discovered about 20 extrasolar planets （16 published）, including the first two Jupiter-Saturn like systems and the only five ＂cold Neptunes＂ yet de- tected. They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation. （3） Microlensing pro- vides a unique way to measure the mass of isolated stars, including brown dwarfs and normal stars. Half a dozen or so stellar mass black hole candidates have also been pro- posed. （4） High-resolution, target-of-opportunity spectra of highly-magnified dwarf stars provide intriguing ＂age＂ determinations which may either hint at enhanced he- lium enrichment or unusual bulge formation theories. （5） Microlensing also measured limb-darkening profiles for close to ten giant stars, which challenges stellar atmo- sphere models. （6） Data from surveys also provide strong constraints on the geometry and kinematics of the Milky Way bar （through proper motions）; the latter indicates predictions from current models appear to be too anisotropic compared with observa- tions. The future of microlensing is bright given the new capabilities of current surveys and forthcoming new telescope networks from the ground and from space. Some open issues in the field are identified and briefly discussed.
基金Supported by the National Natural Science Foundation of China under Grant No 11275035
文摘We study the cosmic constraint to the wCDM （cold dark matter with a constant equation of state w） model via 118 strong gravitational lensing systems which are compiled from SLA CS, BELLS, LSD and SL2S surveys, where the ratio between two angular diameter distances Dobs =DA（Zl, Zs ） / D A （ O, Zs ） is taken as a cosmic observable. To obtain this ratio, we adopt two strong tensing models： one is the singular isothermal sphere model （SIS） and the other one is the power-law density profile （PLP） model. Via the Markov chain Monte Carlo method, the posterior distribution of the cosmological model parameters space is obtained. The results show that the cosmological model parameters are not sensitive to the parameterized forms of the power-law index γ. Furthermore, the PLP model gives a relatively tighter constraint to the cosmological parameters than that of the SIS model. The predicted value of Ωm = 0.31＋0.44 -0.24 by the SIS model is compatible with that obtained by P1anck2015： Ωm = 0.313 ± 0.013. However, the value of Ωm =0.15＋0.13 -0.11 based on the PLP model is smaller and has 1.25σ tension with that obtained by Planck2015.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.U1931210,11673065 and 11273061)funds the NBSDC-DB-10(No.2020000088)the science research grants from the China Manned Space Project with No.CMS-CSST-2021-A12。
文摘Theoretical investigations into the deflection angle caused by microlenses offer a direct path to uncovering principles of the cosmological microlensing effect.This work specifically concentrates on the the probability density function(PDF)of the light deflection angle induced by microlenses.We have made several significant improvements to the widely used formula from Katz et al.First,we update the coefficient from 3.05 to 1.454,resulting in a better fit between the theoretical PDF and our simulation results.Second,we developed an elegant fitting formula for the PDF that can replace its integral representation within a certain accuracy,which is numerically divergent unless arbitrary upper limits are chosen.Third,to facilitate further theoretical work in this area,we have identified a more suitable Gaussian approximation for the fitting formula.
基金supported by the National Natural Science Foundation of China(grant No.11922303)the Natural Science Foundation of Chongqing(grant No.CSTB2023NSCQ-MSX0103)+1 种基金the Key Research Program of Xingtai 2020ZC005the Fundamental Research Funds for the Central Universities(grant No.2042022kf1182)。
文摘The error propagation among estimated parameters reflects the correlation among the parameters.We study the capability of machine learning of"learning"the correlation of estimated parameters.We show that machine learning can recover the relation between the uncertainties of different parameters,especially,as predicted by the error propagation formula.Gravitational lensing can be used to probe both astrophysics and cosmology.As a practical application,we show that the machine learning is able to intelligently find the error propagation among the gravitational lens parameters(effective lens mass ML and Einstein radiusθ_(E))in accordance with the theoretical formula for the singular isothermal ellipse(SIE)lens model.The relation of errors of lens mass and Einstein radius,(e.g.,the ratio of standard deviations F=σ_(ML)/σ_(θ_(E)))predicted by the deep convolution neural network are consistent with the error propagation formula of the SIE lens model.As a proof-of-principle test,a toy model of linear relation with Gaussian noise is presented.We found that the predictions obtained by machine learning indeed indicate the information about the law of error propagation and the distribution of noise.Error propagation plays a crucial role in identifying the physical relation among parameters,rather than a coincidence relation,therefore we anticipate our case study on the error propagation of machine learning predictions could extend to other physical systems on searching the correlation among parameters.
基金funded by the National Natural Science Foundation of China 11975145partly supported by Research Grant FZ-20200929344 and F-FA2021-510 of the Uzbekistan Ministry for Innovative DevelopmentGrant No.ZC304022919 to support his Postdoctoral Fellowship at Zhejiang Normal University
文摘We study the particle dynamics around a black hole(BH)in f(Q)gravity.First,we investigate the influence of the parameters of f(Q)gravity on the horizon structure of the BH,photon orbits and the radius of the innermost stable circular orbit(ISCO)of massive particles.We further study the effects of the parameters of f(Q)gravity on the shadow cast by the BH.Moreover,we consider weak gravitational lensing using the general method,where we also explore the deflection angle of light rays around the BH in f(Q)gravity in uniform and nonuniform plasma mediums.
基金funded by the National Natural Science Foundation of China(NSFC)under Nos.11873006,11933002,11903082,and U1931210the science research grants from the China Manned Space Project with Nos.CMS-CSST-2021-A01,CMS-CSST-2021A12,and CMS-CSST-2021-A07。
文摘Weak gravitational lensing is a powerful tool in modern cosmology.To accurately measure the weak lensing signal,one has to control the systematic bias on a small level.One of the most difficult problems is how to correct the smearing effect of the Point-Spread Function(PSF)on the shape of the galaxies.The chromaticity of PSF for a broad-band observation can lead to new subtle effects.Since the PSF is wavelength-dependent and the spectrum energy distributions between stars and galaxies are different,the effective PSF measured from the star images will be different from those that smear the galaxies.Such a bias is called color bias.We estimate it in the optical bands of the Chinese Space Station Survey Telescope from simulated PSFs,and show the dependence on the color and redshift of the galaxies.Moreover,due to the spatial variation of spectra over the galaxy image,another higher-order bias exists:color gradient bias.Our results show that both color bias and color gradient bias are generally below 0.1%in CSST.Only for small-size galaxies,one needs to be careful about the color gradient bias in the weak lensing analysis using CSST data.
基金supported by the National Natural Science Foundation (Grant No.10673012)CAS (Grant No. KJCX3-SYW-N2)+1 种基金the National Basic Research Program of China (973 ProgramGrant No.2009CB24901)
文摘Cosmological numerical simulations of galaxy formation have led to the cuspy density profile of a pure cold dark matter halo toward the center, which is in sharp contradiction with the observations of the rotation curves of cold dark matter-dominated dwarf and low surface brightness disk galaxies, with the latter tending to favor mass profiles with a flat central core. Many efforts have been devoted to resolving this cusp-core problem in recent years, among them, baryon-cold dark matter interactions are considered to be the main physical mechanisms erasing the cold dark matter （CDM） cusp into a flat core in the centers of all CDM halos. Clearly, baryon-cold dark matter interactions are not customized only for CDM-dominated disk galaxies, but for all types, including giant ellipticals. We first fit the most recent high resolution observations of rotation curves with the Burkert profile, then use the constrained core size-halo mass relation to calculate the lensing frequency, and compare the predicted results with strong lensing observations. Unfortunately, it turns out that the core size constrained from rotation curves of disk galaxies cannot be extrapolated to giant ellipticals. We conclude that, in the standard cosmological paradigm, baryon-cold dark matter interactions are not universal mechanisms for galaxy formation, and therefore, they cannot be true solutions to the cusp-core problem.
基金Supported by Natural Science Foundation of Education Department of Shannxi Provincial Government under Grant No.15JK1077Doctorial Scientific Research Starting Fund of Shannxi University of Science and Technology under Grant No.BJ12-02
文摘A class of braneworld black holes, which I called as Bronnikov–Melnikov–Dehen(BMD) black holes,are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate the angular positions and magnifications of relativistic images as well as the time delay between different relativistic images. I also compare the results with those obtained for Schwarzschild and two braneworld black holes, i.e., the tidal Reissner-Nordstr¨om(R-N) and the Casadio–Fabbri–Mazzacurati(CFM) black holes.
