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
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
The power-law parametrization for the energy density spectrum of gravitational wave(GW)background is a useful tool to study its physics and origin.While scalar induced secondary gravitational waves(SIGWs)from some par...The power-law parametrization for the energy density spectrum of gravitational wave(GW)background is a useful tool to study its physics and origin.While scalar induced secondary gravitational waves(SIGWs)from some particular models fit the signal detected by NANOGrav,Parkers Pulsar Timing Array,European Pulsar Timing Array,and Chinese Pulsar Timing Array collaborations better than GWs from supermassive black hole binaries(SMBHBs),we test the consistency of the data with the infrared part of SIGWs which is somewhat independent of models.Through Bayesian analysis,we show that the infrared parts of SIGWs fit the data better than GW background from SMBHBs.The results give tentative evidence for SIGWs.展开更多
We consider the polynomial inflation with the tensor-to-scalar ratio as large as possible which can be consistent with the quantum gravity(QG) corrections and effective field theory(EFT). To get a minimal field excurs...We consider the polynomial inflation with the tensor-to-scalar ratio as large as possible which can be consistent with the quantum gravity(QG) corrections and effective field theory(EFT). To get a minimal field excursion ΔΦ for enough e-folding number N, the inflaton field traverses an extremely flat part of the scalar potential, which results in the Lyth bound to be violated. We get a CMB signal consistent with Planck data by numerically computing the equation of motion for inflaton Φ and using Mukhanov–Sasaki formalism for primordial spectrum. Inflation ends at Hubble slow-roll parameter ε_(1)^(H)=1 or a=0. Interestingly, we find an excellent practical bound on the inflaton excursion in the format a+b√r, where a is a tiny real number and b is at the order 1. To be consistent with QG/EFT and suppress the high-dimensional operators, we show that the concrete condition on inflaton excursion is M_(PI)/△_(Ф)<0.2×√10≈0.632. For n_(s)= 0.9649,N_(e)= 55, and M_(PI)/△_(Ф)<0.632 MPl, we predict that the tensor-to-scalar ratio is smaller than 0.0012 for such polynomial inflation to be consistent with QG/EFT.展开更多
With the usual definitions for the entropy and the temperature associated with the apparent horizon, we discuss the first law of the thermodynamics on the apparent in the general scalar-tensor theory of gravity with t...With the usual definitions for the entropy and the temperature associated with the apparent horizon, we discuss the first law of the thermodynamics on the apparent in the general scalar-tensor theory of gravity with the kinetic term of the scalar field nonminimally coupling to Einstein tensor. We show the equivalence between the first law of thermodynamics on the apparent horizon and Friedmann equation for the general models, by using a mass-like function which is equal to the Misner-Sharp mass on the apparent horizon. The results further support the universal relationship between the first law of thermodynamics and Friedmann equation.展开更多
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.
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 Key Research and Development Program of China(Grant No.2020YFC2201504)the National Natural Science Foundation of China(Grant No.12175184)+2 种基金supported by the National Natural Science Foundation of China(Grant No.12205015)the supporting fund for Young Researcher of Beijing Normal University(Grant No.28719/310432102)supported by the National Natural Science Foundation of China(Grant No.12305075)。
文摘The power-law parametrization for the energy density spectrum of gravitational wave(GW)background is a useful tool to study its physics and origin.While scalar induced secondary gravitational waves(SIGWs)from some particular models fit the signal detected by NANOGrav,Parkers Pulsar Timing Array,European Pulsar Timing Array,and Chinese Pulsar Timing Array collaborations better than GWs from supermassive black hole binaries(SMBHBs),we test the consistency of the data with the infrared part of SIGWs which is somewhat independent of models.Through Bayesian analysis,we show that the infrared parts of SIGWs fit the data better than GW background from SMBHBs.The results give tentative evidence for SIGWs.
基金supported in part by the Projects 11875062, 11875136, and 11947302supported by the National Natural Science Foundation of China+3 种基金the Major Program of the National Natural Science Foundation of China under Grant No. 11690021the Key Research Program of Frontier Science, CASsupported in part by the Program 2020JQ-804 supported by Natural Science Basic Research Plan in Shanxi Province of Chinathe Program 20JK0685 funded by Shanxi Provincial Education Department。
文摘We consider the polynomial inflation with the tensor-to-scalar ratio as large as possible which can be consistent with the quantum gravity(QG) corrections and effective field theory(EFT). To get a minimal field excursion ΔΦ for enough e-folding number N, the inflaton field traverses an extremely flat part of the scalar potential, which results in the Lyth bound to be violated. We get a CMB signal consistent with Planck data by numerically computing the equation of motion for inflaton Φ and using Mukhanov–Sasaki formalism for primordial spectrum. Inflation ends at Hubble slow-roll parameter ε_(1)^(H)=1 or a=0. Interestingly, we find an excellent practical bound on the inflaton excursion in the format a+b√r, where a is a tiny real number and b is at the order 1. To be consistent with QG/EFT and suppress the high-dimensional operators, we show that the concrete condition on inflaton excursion is M_(PI)/△_(Ф)<0.2×√10≈0.632. For n_(s)= 0.9649,N_(e)= 55, and M_(PI)/△_(Ф)<0.632 MPl, we predict that the tensor-to-scalar ratio is smaller than 0.0012 for such polynomial inflation to be consistent with QG/EFT.
基金supported by the National Natural Science Foundation of China(Grant Nos.11175270 and 11475065)the Program for New Century Excellent Talents in University(Grant No.NCET-12-0205)
文摘With the usual definitions for the entropy and the temperature associated with the apparent horizon, we discuss the first law of the thermodynamics on the apparent in the general scalar-tensor theory of gravity with the kinetic term of the scalar field nonminimally coupling to Einstein tensor. We show the equivalence between the first law of thermodynamics on the apparent horizon and Friedmann equation for the general models, by using a mass-like function which is equal to the Misner-Sharp mass on the apparent horizon. The results further support the universal relationship between the first law of thermodynamics and Friedmann equation.