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On the improved dynamics approach in loop quantum black holes

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Communications in Theoretical Physics 2024年第3期76卷 138-143页

作者： Hongchao Zhang Wen-Cong Gan yungui gong Anzhong Wang Institute for Theoretical Physics&Cosmology Zhejiang University of TechnologyHangzhou310023China United Center for Gravitational Wave Physics(UCGWP) Zhejiang University of TechnologyHangzhou310023China College of Physics and Communication Electronics Jiangxi Normal UniversityNanchang 330022China GCAP-CASPER Physics DepartmentBaylor UniversityWacoTX 76798-7316United States of America School of Physics Huazhong University of Science and TechnologyWuhanHubei 430074China Department of Physics School of Physical Science and TechnologyNingbo UniversityNingboZhejiang 315211China

In this paper,we consider the B?hmer–Vandersloot(BV)model of loop quantum black holes obtained from the improved dynamics *** adopt the Saini–Singh gauge,in which it was found analytically that the BV spacetime is geodesically *** show that black/white hole horizons do not exist in this geodesically complete ***,there exists only an infinite number of transition surfaces,which always separate trapped regions from anti-trapped *** on the improved dynamics approach adopted in other models of loop quantum black holes are also given.

关键词： loop quantum gravity black hole dynamics approach

Nonexistence of quantum black and white hole horizons in an improved dynamic approach

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Science China(Physics,Mechanics & Astronomy) 2024年第8期67卷 56-73页

作者： Wen-Cong Gan Xiao-Mei Kuang Zhen-Hao Yang yungui gong Anzhong Wang Bin Wang College of Physics and Communication Electronics Jiangxi Normal UniversityNanchang 330022China GCAP-CASPER Physics DepartmentBaylor UniversityWaco 76798-7316USA Institute for Theoretical Physics&Cosmology Zhejiang University of TechnologyHangzhou 310023China United Center for Gravitational Wave Physics(UCGWP) Zhejiang University of TechnologyHangzhou 310023China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China Department of Physics School of Physical Science and TechnologyNingbo UniversityNingbo 315211China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China

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 *** 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 *** surfaces always separate trapped regions from anti-trapped *** 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.

关键词： canonical quantization loop quantum gravity quantum aspects of black holes

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Thermodynamics of general scalar-tensor theory with non-minimally derivative coupling

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Science China(Physics,Mechanics & Astronomy) 2016年第4期59卷 37-41页

作者： YuMei Huang yungui gong Institute of Physics and Electric Engineering Mianyang Normal University Department of Astronomy Beijing Normal University School of Physics Huazhong University of Science and Technology

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.

关键词： modified gravity thermodynamics derivative coupling cosmology

Scalar induced gravitational waves in light of Pulsar Timing Array data

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Science China(Physics,Mechanics & Astronomy) 2023年第12期66卷 20-28页

作者： Zhu Yi Qing Gao yungui gong Yue Wang Fengge Zhang Advanced Institute of Natural Sciences Beijing Normal UniversityZhuhai 519087China School of Physical Science and Technology Southwest UniversityChongqing 400715China School of Physics Huazhong University of Science and TechnologyWuhan 430074China Department of Physics School of Physical Science and TechnologyNingbo UniversityNingbo 315211China School of Physics and Astronomy Sun Yat-sen UniversityZhuhai 519088China

The power-law parametrization for the energy density spectrum of gravitational wave(GW)background is a useful tool to study its physics and *** 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 *** Bayesian analysis,we show that the infrared parts of SIGWs fit the data better than GW background from *** results give tentative evidence for SIGWs.

关键词： SIGWs PTA data infrared region

Simple single field inflation models and the running of spectral index

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Science China(Physics,Mechanics & Astronomy) 2014年第8期57卷 1442-1448页

作者： GAO Qing gong yungui LI TianJun YE Tian MOE Key Laboratory of Fundamental Quantities Measurement School of Physics Huazhong University of Science and Technology State Key Laboratory of Theoretical Physics and Kavli Institute for Theoretical Physics China Institute of Theoretical Physics Chinese Academy of Sciences School of Physical Electronics University of Electronic Science and Technology of China

The BICEP2 experiment confirms the existence of primordial gravitational wave with the tensor-to-scalar ratio r = 0 ruled out at 70- level. The consistency of this large value of r with the Planck data requires a large negative running n＇s of the scalar spectral index. Herein we propose two types of the single field inflation models with simple potentials to study the possibility of the consistency of the models with the BICEP2 and Planck observations. One type of model suggested herein is realized in the supergravity model building. These models fail to provide the needed n＇s even though both can fit the tensor-to-scalar ratio and spectral index.

关键词： single field inflation BICEP2 results supergravity model building

The upper bound on the tensor-to-scalar ratio consistent with quantum gravity

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Communications in Theoretical Physics 2021年第7期73卷 115-120页

作者： Lina Wu Qing Gao yungui gong Yiding Jia Tianjun Li School of Sciences Xi’an Technological UniversityXi’an 710021China School of Physical Science and Technology Southwest UniversityChongqing 400715China School of Physics Huazhong University of Science and TechnologyWuhanHubei 430074China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

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.

关键词： polynomail inflation Lyth bound tensor-to-scalar ratio

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引引力波偏振

科学通报 2018年第9期63卷 801-815页

作者：郜青龚云贵梁迪聪西南大学物理科学与技术学院重庆400715 华中科技大学物理学院武汉430074

引力波的直接观测不但开启了一扇探测引力本质的全新窗口,而且使我们进入了多信使引力波天文学时代.引力波不影响单个检验粒子的测地线运动,其偏振态由两个相邻检验粒子的相对运动,即测地线偏离运动所决定.测地线偏离方程中只出现黎曼... 详细信息

引力波的直接观测不但开启了一扇探测引力本质的全新窗口,而且使我们进入了多信使引力波天文学时代.引力波不影响单个检验粒子的测地线运动,其偏振态由两个相邻检验粒子的相对运动,即测地线偏离运动所决定.测地线偏离方程中只出现黎曼张量的电分量,它有6个独立分量,所以在最一般的度规引力理论中,引力波最多可以有6种偏振模式.这6种偏振模式分别为:"+"偏振态、"×"偏振态、呼吸偏振态、矢量-x偏振态、矢量-y偏振态及纵振态.爱因斯坦广义相对论中的引力波只有"+"与"×"两个张量偏振态,Brans-Dicke理论中的引力波除了"+"与"×"偏振态外,还有一个呼吸偏振态.在Horndeski及f(R)理论中,引力波除了"+"与"×"两个张量偏振态外,还有一个由呼吸模与纵振模混合而成的标量偏振态.在爱因斯坦-以太理论中,非零矢量场的出现破坏了局域洛伦兹对称性,该理论中的引力波以非光速传播,且具有5个独立偏振态.张量-矢量-标量理论中的引力波传播速度与光速不同,且该理论中的引力波具有6个独立偏振态.因为不同引力理论中的引力波偏振态不同,所以引力波偏振态的测量可用于探究引力本质.

关键词：引力波偏振态标量-张量理论爱因斯坦-以太理论张量-矢量-标量理论

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引力波及引力理论检验

中山大学学报（自然科学版） 2021年第1期60卷 86-98页

作者：郜青龚云贵龙江西南大学物理科学与技术学院重庆400715 华中科技大学物理学院湖北武汉430074

爱因斯坦广义相对论预言时空涟漪以引力波的形式向外传播,它的传播速度是光速,具有两个偏振态。超越爱因斯坦广义相对论的修改引力理论则预言引力波可能存在纵模及多至六个偏振模式,引力波的传播速度不是光速,引力子可能具有质量,且引... 详细信息

爱因斯坦广义相对论预言时空涟漪以引力波的形式向外传播,它的传播速度是光速,具有两个偏振态。超越爱因斯坦广义相对论的修改引力理论则预言引力波可能存在纵模及多至六个偏振模式,引力波的传播速度不是光速,引力子可能具有质量,且引力波也可能存在偶极辐射。本文介绍了引力波的性质,以及怎样通过引力波的探测来可能检验引力理论。

关键词：引力波引力理论

Hydrolysis enhancing mechanisms of Mg-based alloys/hydrides from perspectives:Electrochemical corrosion,active sites,mass transfer,and kinetics

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Journal of Materials Science & Technology 2023年第32期163卷 1-16页

作者： Chaoling Wu Qin Huang Bingshou gong Ji Zhou Guanghui Xia Fangnan He Yao Wang Yigang Yan yungui Chen Department of Advanced Energy Materials College of Materials Science and EngineeringSichuan UniversityChengdu 610042China Institute of New Energy and Low-Carbon Technology Sichuan UniversityChengdu 610065China Engineering Research Center of Alternative Energy Materials&Devices Ministry of EducationChengdu 610064China Technology Innovation Center of Hydrogen Storage-Transportation and Fueling Equipments for State Market Regulation Chengdu 610000China

Hydrogen energy is considered to be an ideal new energy carrier in the 21st century due to its clean,environmentally friendly,renewable characteristics and high energy *** generation of hydrogen by hydrolysis of Mg-based alloys/hydrides has attracted extensive attention attributed to the high hydrogen yield,environmentally-benign by-products,high crust abundance,and well-developed industrial production of ***,in the hydrolysis process of Mg or MgH_(2)to generate hydrogen,the formed Mg(OH)_(2)passivation layer attaches to the surface of the active materials to prevent the reaction from *** improve the hydrolysis performance,a series of methods have been put *** this paper,focusing on the mechanisms of hydrogen generation by hydrolysis of Mg-based alloys/hydrides,we summarize the recent research progress from four different perspectives:electrochemical corrosion promotion by constructing galvanic cells,active sites increment by refining the particles,mass transfer enhancement by breaking Mg(OH)_(2)and corresponding kinetic improvement.

关键词： Hydrogen generation Hydrolysis Mg MgH2