We constrain cosmological parameters using only Hubble parameter data and quantify the impact of future Hubble parameter measurements on parameter estimation for the most typical dark energy models. We first constrain...We constrain cosmological parameters using only Hubble parameter data and quantify the impact of future Hubble parameter measurements on parameter estimation for the most typical dark energy models. We first constrain cosmological parameters using 52 current Hubble parameter data including the Hubble constant measurement from the Hubble Space Telescope. Then we simulate the baryon acoustic oscillation signals from WFIRST(Wide-Field Infrared Survey Telescope) covering the redshift range of z ∈ [0.5, 2] and the redshift drift data from E-ELT(European Extremely Large Telescope) in the redshift range of z ∈ [2, 5]. It is shown that solely using the current Hubble parameter data could give fairly good constraints on cosmological parameters. Compared to the current Hubble parameter data, with the WFIRST observation the H(z) constraints on dark energy would be improved slightly, while with the E-ELT observation the H(z) constraints on dark energy is enormously improved.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
Recently the background independent nonperturbative quantization has been extended to various theories of gravity and the corresponding quantum effective cosmology has been derived, which provides us with necessary av...Recently the background independent nonperturbative quantization has been extended to various theories of gravity and the corresponding quantum effective cosmology has been derived, which provides us with necessary avenue to explore the pre-inflationary dynamics. Brans-Dicke(BD) loop quantum cosmology(LQC) is one of such theories whose effective background dynamics is considered in this article. Starting with a quantum bounce, we explore the pre-inflationary dynamics of a universe sourced by a scalar field with the Starobinsky potential in BD-LQC. Our study is based on the idea that though Einstein’s and Jordan’s frames are classically equivalent up to a conformal transformation in BD theory, this is no longer true after quantization. Taking the Jordan frame as the physical one we explore in detail the bouncing scenario which is followed by a phase of a slow roll inflation. The three phases of the evolution of the universe, namely, bouncing, transition from quantum bounce to classical universe, and the slow roll inflation, are noted for an initially kinetic energy dominated bounce. In addition, to be consistent with observations, we also identify the allowed phase space of initial conditions that would produce at least 60 e-folds of expansion during the slow roll inflation.展开更多
In this paper,we consider the B?hmer–Vandersloot(BV)model of loop quantum black holes obtained from the improved dynamics approach.We adopt the Saini–Singh gauge,in which it was found analytically that the BV spacet...In this paper,we consider the B?hmer–Vandersloot(BV)model of loop quantum black holes obtained from the improved dynamics approach.We adopt the Saini–Singh gauge,in which it was found analytically that the BV spacetime is geodesically complete.We show that black/white hole horizons do not exist in this geodesically complete spacetime.Instead,there exists only an infinite number of transition surfaces,which always separate trapped regions from anti-trapped ones.Comments on the improved dynamics approach adopted in other models of loop quantum black holes are also given.展开更多
In this paper we analyze and discuss 2D Jackiw-Teitelboim(JT)gravity coupled to primary fermion fields in asymptotically anti-de Sitter(AdS)spacetimes.We obtain a particular solution of the massless Dirac field outsid...In this paper we analyze and discuss 2D Jackiw-Teitelboim(JT)gravity coupled to primary fermion fields in asymptotically anti-de Sitter(AdS)spacetimes.We obtain a particular solution of the massless Dirac field outside the extremal black hole horizon and find the solution for the dilaton in JT gravity.As two dimensional JT gravity spacetime is conformally flat,we calculate the two point correlators of primary fermion fields under the Weyl transformations.The primary goal of this work is to present a standard technique,called resolvent,rather than using CFT methods.We redefine the fields in terms of the conformal factor as fermion fields and use the resolvent technique to derive the renormalized entanglement entropy for massless Dirac fields in JT gravity.展开更多
The successful observation of gravitational waves has provided humanity with an additional method to explore the universe,particularly black holes.In this study,we utilize data from LIGO and Virgo gravitational wave o...The successful observation of gravitational waves has provided humanity with an additional method to explore the universe,particularly black holes.In this study,we utilize data from LIGO and Virgo gravitational wave observations to test the first law of black hole mechanics,employing two different approaches.We consider the secondary compact object as a perturbation to the primary black hole before the merger,and the remnant black hole as a stationary black hole after the merger.In the pre-merger and post-merger analysis,our results demonstrate consistency with the first law,with an error level of approximate 25%at a68%credibility level for GW190403051519.In the full inspiral-merger-ringdown analysis,our results show consistency with the first law of black hole mechanics,with an error level of about 6%at a 68%credibility level and 10%at a 95%credibility level for GW191219163120.Additionally,we observe that the higher the mass ratio of the gravitational wave source,the more consistent our results are with the first law of black hole mechanics.Overall,our study sheds light on the nature of compact binary coalescence and their implications for black hole mechanics.展开更多
In this paper,the gauge choices in general spherically symmetric spacetimes are explored.In particular,we construct the gauge invariant variables and the master equations for both the Detweiler easy gauge and the Regg...In this paper,the gauge choices in general spherically symmetric spacetimes are explored.In particular,we construct the gauge invariant variables and the master equations for both the Detweiler easy gauge and the Regge-Wheeler gauge,respectively.The particular cases for l=0,1 are also investigated.Our results provide analytical calculations of metric perturbations in general spherically symmetric spacetimes,which can be applied to various cases,including the effective-one-body problem.A simple example is presented to show how the metric perturbation components are related to the source perturbation terms.展开更多
In this paper,we study the quantum geometric effects near the locations where classical black hole horizons used to appear in Einstein's classical theory,within the framework of an improved dynamic approach,in whi...In this paper,we study the quantum geometric effects near the locations where classical black hole horizons used to appear in Einstein's classical theory,within the framework of an improved dynamic approach,in which the internal region of a black hole is modeled by the Kantowski-Sachs(KS)spacetime and the two polymerization parameters are functions of the phase space variables.Our detailed analysis shows that the effects are so strong that black and white hole horizons of the effective quantum theory do not exist at all and instead are replaced by transition surfaces,across which the metric coefficients and their inverses are smooth and remain finite,as are the corresponding curvatures,including the Kretschmann scalar.These surfaces always separate trapped regions from anti-trapped regions.The number of such surfaces is infinite,so the corresponding KS spacetimes become geodesically complete,and no black and white hole-like structures exist in this scheme.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.11522540,11690021,11375153,11675145the National Program for Support of Top-Notch Young Professionalsthe 2016 Program for Postdoctoral Fellowship of Zhejiang Province
文摘We constrain cosmological parameters using only Hubble parameter data and quantify the impact of future Hubble parameter measurements on parameter estimation for the most typical dark energy models. We first constrain cosmological parameters using 52 current Hubble parameter data including the Hubble constant measurement from the Hubble Space Telescope. Then we simulate the baryon acoustic oscillation signals from WFIRST(Wide-Field Infrared Survey Telescope) covering the redshift range of z ∈ [0.5, 2] and the redshift drift data from E-ELT(European Extremely Large Telescope) in the redshift range of z ∈ [2, 5]. It is shown that solely using the current Hubble parameter data could give fairly good constraints on cosmological parameters. Compared to the current Hubble parameter data, with the WFIRST observation the H(z) constraints on dark energy would be improved slightly, while with the E-ELT observation the H(z) constraints on dark energy is enormously improved.
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Supported in part by the National Natural Science Foundation of China(NNSCF)under Grant Nos.11375153 and 11675145T.Z.is supported in part by NFSC under Grant No.11675143the Fundamental Research Funds for the Provincial Universities of Zhejiang in China under Grant No.RF-A2019015
文摘Recently the background independent nonperturbative quantization has been extended to various theories of gravity and the corresponding quantum effective cosmology has been derived, which provides us with necessary avenue to explore the pre-inflationary dynamics. Brans-Dicke(BD) loop quantum cosmology(LQC) is one of such theories whose effective background dynamics is considered in this article. Starting with a quantum bounce, we explore the pre-inflationary dynamics of a universe sourced by a scalar field with the Starobinsky potential in BD-LQC. Our study is based on the idea that though Einstein’s and Jordan’s frames are classically equivalent up to a conformal transformation in BD theory, this is no longer true after quantization. Taking the Jordan frame as the physical one we explore in detail the bouncing scenario which is followed by a phase of a slow roll inflation. The three phases of the evolution of the universe, namely, bouncing, transition from quantum bounce to classical universe, and the slow roll inflation, are noted for an initially kinetic energy dominated bounce. In addition, to be consistent with observations, we also identify the allowed phase space of initial conditions that would produce at least 60 e-folds of expansion during the slow roll inflation.
基金partially supported by the National Key Research and Development Program of China under Grant No.2020YFC2201504partially supported by a NSF grant with the grant number:PHY2308845。
文摘In this paper,we consider the B?hmer–Vandersloot(BV)model of loop quantum black holes obtained from the improved dynamics approach.We adopt the Saini–Singh gauge,in which it was found analytically that the BV spacetime is geodesically complete.We show that black/white hole horizons do not exist in this geodesically complete spacetime.Instead,there exists only an infinite number of transition surfaces,which always separate trapped regions from anti-trapped ones.Comments on the improved dynamics approach adopted in other models of loop quantum black holes are also given.
基金Supported by the National Natural Science Foundation of China(11975116)。
文摘In this paper we analyze and discuss 2D Jackiw-Teitelboim(JT)gravity coupled to primary fermion fields in asymptotically anti-de Sitter(AdS)spacetimes.We obtain a particular solution of the massless Dirac field outside the extremal black hole horizon and find the solution for the dilaton in JT gravity.As two dimensional JT gravity spacetime is conformally flat,we calculate the two point correlators of primary fermion fields under the Weyl transformations.The primary goal of this work is to present a standard technique,called resolvent,rather than using CFT methods.We redefine the fields in terms of the conformal factor as fermion fields and use the resolvent technique to derive the renormalized entanglement entropy for massless Dirac fields in JT gravity.
基金supported by the National Natural Science Foundation of China(Grant Nos.12375049,and 11975116)the Key Program of the Natural Science Foundation of Jiangxi Province(Grant No.20232ACB201008)+3 种基金funded by the U.S.National Science Foundationfunded by the French Centre National de Recherche Scientifique(CNRS)the Italian Istituto Nazionale della Fisica Nucleare(INFN)the Dutch Nikhef,with contributions by Polish and Hungarian institutes。
文摘The successful observation of gravitational waves has provided humanity with an additional method to explore the universe,particularly black holes.In this study,we utilize data from LIGO and Virgo gravitational wave observations to test the first law of black hole mechanics,employing two different approaches.We consider the secondary compact object as a perturbation to the primary black hole before the merger,and the remnant black hole as a stationary black hole after the merger.In the pre-merger and post-merger analysis,our results demonstrate consistency with the first law,with an error level of approximate 25%at a68%credibility level for GW190403051519.In the full inspiral-merger-ringdown analysis,our results show consistency with the first law of black hole mechanics,with an error level of about 6%at a 68%credibility level and 10%at a 95%credibility level for GW191219163120.Additionally,we observe that the higher the mass ratio of the gravitational wave source,the more consistent our results are with the first law of black hole mechanics.Overall,our study sheds light on the nature of compact binary coalescence and their implications for black hole mechanics.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFC2201503)National Natural Science Foundation of China(Grant Nos.11705053,11975203,and 12035005)+1 种基金Hunan Provincial Natural Science Foundation of China(Grant No.2022JJ40262)supported in part by China Scholarship Council for the Visiting Post-doc Program at Baylor University。
文摘In this paper,the gauge choices in general spherically symmetric spacetimes are explored.In particular,we construct the gauge invariant variables and the master equations for both the Detweiler easy gauge and the Regge-Wheeler gauge,respectively.The particular cases for l=0,1 are also investigated.Our results provide analytical calculations of metric perturbations in general spherically symmetric spacetimes,which can be applied to various cases,including the effective-one-body problem.A simple example is presented to show how the metric perturbation components are related to the source perturbation terms.
基金supported by Baylor University through the Baylor Physics graduate programsupported by the Initial Research Foundation of Jiangxi Normal University(Grant No.12022827)+3 种基金partially supported by the National Key Research and Development Program of China(Grant No.2020YFC2201504)the National Natural Science Foundation of China(Grant Nos.11975203,12075202,and 11875136)the Natural Science Foundation of Jiangsu Province(Grant No.BK20211601)partially supported by the National Science Foundation(Grant No.PHY2308845)。
文摘In this paper,we study the quantum geometric effects near the locations where classical black hole horizons used to appear in Einstein's classical theory,within the framework of an improved dynamic approach,in which the internal region of a black hole is modeled by the Kantowski-Sachs(KS)spacetime and the two polymerization parameters are functions of the phase space variables.Our detailed analysis shows that the effects are so strong that black and white hole horizons of the effective quantum theory do not exist at all and instead are replaced by transition surfaces,across which the metric coefficients and their inverses are smooth and remain finite,as are the corresponding curvatures,including the Kretschmann scalar.These surfaces always separate trapped regions from anti-trapped regions.The number of such surfaces is infinite,so the corresponding KS spacetimes become geodesically complete,and no black and white hole-like structures exist in this scheme.
