COSMIC-2(constellation observing system for meteorology ionosphere and climate-2)作为COSMIC掩星星座的后续计划,得益于升级了支持多模GNSS信号的接收机和高增益定向波束掩星天线,其观测数据质量和数量得到显著提升。围绕掩星观...COSMIC-2(constellation observing system for meteorology ionosphere and climate-2)作为COSMIC掩星星座的后续计划,得益于升级了支持多模GNSS信号的接收机和高增益定向波束掩星天线,其观测数据质量和数量得到显著提升。围绕掩星观测数据和反演产品的定量评估,分析COSMIC-2定轨和掩星天线的原始观测数据质量,并以欧洲中期数值天气预报中心的再分析气象资料为基准,定量评估掩星反演大气廓线产品质量。结果显示,COSMIC-2定轨天线L1频段信噪比大多在45 dB以上,其对应伪距多路径效应中误差在0.2~0.4 m之间;掩星天线观测信噪比由第一代COSMIC的不足700 v/v大幅提升至1200 v/v,且GLONASS掩星廓线和GPS掩星廓线均与气象再分析资料表现出了很好的一致性。研究结果认为,升级后的COSMIC-2掩星载荷不仅大幅增加掩星观测数量,其高增益的掩星天线设计还有效地提升了掩星观测数据质量,为大气科学研究提供了重要气象观测资料。展开更多
Let F_(1)be the virtual field consisting of one element and(Q,I)a string pair.In this paper,we study the representations of string pairs over the virtual field F_(1).It is proved that an indecomposable F_(1)-represent...Let F_(1)be the virtual field consisting of one element and(Q,I)a string pair.In this paper,we study the representations of string pairs over the virtual field F_(1).It is proved that an indecomposable F_(1)-representation is either a string representation or a band representation by using the coefficient quivers.It is worth noting that for a given band and a positive integer,there exists a unique band representation up to isomorphism.展开更多
In this paper, in Section 1, we have described some equations and theorems concerning the Lebesgue integral and the Lebesgue measure. In Section 2, we have described the possible mathematical applications, of Lebesgue...In this paper, in Section 1, we have described some equations and theorems concerning the Lebesgue integral and the Lebesgue measure. In Section 2, we have described the possible mathematical applications, of Lebesgue integration, in some equations concerning various sectors of Chern-Simons theory and Yang-Mills gauge theory, precisely the two dimensional quantum Yang-Mills theory. In conclusion, in Section 3, we have described also the possible mathematical connections with some sectors of String Theory and Number Theory, principally with some equations concerning the Ramanujan’s modular equations that are related to the physical vibrations of the bosonic strings and of the superstrings, some Ramanujan’s identities concerning π and the zeta strings.展开更多
This is a writeup of lectures delivered at the Asian Pacific Introductory School on Superstring and Related Topics in Beijing(2006)and an expanded version of these lectures given at the Third Summer School on Strings,...This is a writeup of lectures delivered at the Asian Pacific Introductory School on Superstring and Related Topics in Beijing(2006)and an expanded version of these lectures given at the Third Summer School on Strings,Fields and Holography in Nanjing(2023).It aims to provide both a historical and pedagogical account of developments in finding 1/2 Bogomol?nyi–Prasad–Sommerfield(BPS)extended string solitons during the early stage of the so-called second string revolution,before which these objects were thought to be unrelated to strings.Nonsupersymmetric solutions related to brane/anti brane systems or non-BPS systems are also discussed.展开更多
During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a nu...During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a numerical model is developed to simulate the effects of repeated loading on rock fatigue and failure.The simulation is based on an elasto-plastic constitutive model coupled with a damage mechanics approach,which allows us to examine the wellbore instability due to drill string vibrations.The model is verified with the existing data in the literature related to experiments on impact of a steel ball against a curved wall.The findings indicate that cyclic loading increases the development of plastic strain around the wellbore significantly compared to static conditions,promoting rock fatigue.Furthermore,the cyclic loading expands the radius of the yielded zone substantially,a critical factor for maintaining wellbore integrity.The proposed model can be used to evaluate the wellbore stability under repetitive loading caused by the drill string action.展开更多
A new phenomenological model(axionic QCD string)is constructed to study the topological issues of the QCD vacuum and hadron structure.It provides an alternative way of tackling the Strong CP problem,which is different...A new phenomenological model(axionic QCD string)is constructed to study the topological issues of the QCD vacuum and hadron structure.It provides an alternative way of tackling the Strong CP problem,which is different from the traditional Peccei–Quinn approach.Neither new particle nor extra symmetry is introduced,and the role of the Peccei–Quinn axion is played by a quasiparticle arising from the phase of the quark condensate,dubbed as axionic excitation.The derivative of this excitation field is decomposed into a regular part and a singular part,and the latter contains vorticity from the string configuration.A hidden gauge symmetry is revealed in this decomposition and vorticity is represented by an emergent gauge field associated with anomalies.These components,together with the anomaly-inflow mechanism,complete the effective Lagrangian description for the axionic QCD string.展开更多
In this paper we consider a static spherically symmetric black hole(BH)embedded in a Dehnen-(1,4,0)-type dark matter(DM)halo in the presence of a cloud string.We examine and present data on how the core density of the...In this paper we consider a static spherically symmetric black hole(BH)embedded in a Dehnen-(1,4,0)-type dark matter(DM)halo in the presence of a cloud string.We examine and present data on how the core density of the DM halo parameter and the cloud string parameter affect BH attributes such as quasinormal modes(QNMs)and shadow cast.To do this,we first look into the effective potential of perturbation equations for three types of perturbation fields with different spins:massless scalar field,electromagnetic field and gravitational field.Then,using the sixth-order Wentzel-Kramers-Brillouin approximation,we examine QNMs of the BH disturbed by the three fields and derive quasinormal frequencies.The changes in QNM versus the core density parameter and the cloud string parameter for three disturbances are explored.We also investigate how the core density and the cloud string parameter affect the photon sphere and shadow radius.Interestingly,the study shows that the influence of Dehnen-type DM and cloud strings increases both the photon sphere and the shadow radius.Finally,we employ observational data from Sgr A^(*) and M87^(*) to set limitations on the BH parameters.展开更多
The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of dril...The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of drill string.Due to the super slenderness ratio of drill string,strong nonlinearity implied in dynamic analysis and the complex load environment,dynamic simulation of drill string faces great challenges.At present,many simulation methods have been developed to analyze drill string dynamics,and node iteration method is one of them.The node iteration method has a unique advantage in dealing with the contact characteristics between drill string and borehole wall,but its drawback is that the calculation consumes a considerable amount of time.This paper presents a dynamic simulation method of drilling string in extra-deep well based on successive over-relaxation node iterative method(SOR node iteration method).Through theoretical analysis and numerical examples,the correctness and validity of this method were verified,and the dynamics characteristics of drill string in extra-deep wells were calculated and analyzed.The results demonstrate that,in contrast to the conventional node iteration method,the SOR node iteration method can increase the computational efficiency by 48.2%while achieving comparable results.And the whirl trajectory of the extra-deep well drill string is extremely complicated,the maximum rotational speed downhole is approximately twice the rotational speed on the ground.The dynamic torque increases rapidly at the position of the bottom stabilizer,and the lateral vibration in the middle and lower parts of drill string is relatively intense.展开更多
We investigate the relationship between the magnitudes of Forbush decreases(FDs)and solar-geomagnetic characteristics using daily-averaged galactic cosmic ray(GCR)data from Inuvick(INVK)and Magadan(MGDN)neutron monito...We investigate the relationship between the magnitudes of Forbush decreases(FDs)and solar-geomagnetic characteristics using daily-averaged galactic cosmic ray(GCR)data from Inuvick(INVK)and Magadan(MGDN)neutron monitor(NM)stations to aid in counting the case of GCR flux intensity modulation.The FDs,obtained with an automated new computer software algorithm from daily-averaged GCR data from the IZMIRAN common website:http://cr0.izmiran.ru/common,at INVK(224)and MGDN(229)NM stations,from 1998 to 2002,were used in the present work.The associated solar-geomagnetic parameters of the same time range were obtained from the OMNI website.A statistical analytical method was employed to test the link between FD amplitudes and solargeomagnetic variables.We observed negative trends in FD-IMF,FD-SWS,FD-Kp,FD-SSN and FD-SI,while a positive relation was indicated in FD-Dst at both stations.All are statistically significant at a 95%confidence level.The results obtained here imply that solar emission characteristics impact the GCR flux intensity modulation.展开更多
利用2006—2020年中国区域的COSMIC-1/2(constellation observing system for meteorology ionosphere and climate-1/2)IonPrf产品数据,分析了中国区域电离层时空变化特征。首先介绍新一代COSMIC-2在中国以及全球区域的数据质量状况;...利用2006—2020年中国区域的COSMIC-1/2(constellation observing system for meteorology ionosphere and climate-1/2)IonPrf产品数据,分析了中国区域电离层时空变化特征。首先介绍新一代COSMIC-2在中国以及全球区域的数据质量状况;然后对IonPrf产品的数据质量控制和电离层特征参数提取方法进行说明;最后,以不同时间尺度统计分析了中国区域近15年电离层特征参数在一个完整太阳活动周期不同活动水平下的时空变化特征。统计结果表明,中国区域电离层变化具有与太阳活动相关的周年变化、季节变化和日变化特征;周年变化中具有明显空间分布特征,以30°N左右为界,中国南方地区峰值密度NmF2、峰值高度HmF2和电子总含量(total electron content,TEC)年均值普遍高于北方地区;在月份季节变化中,NmF2和TEC最大值一般出现在3月、10月,最小值出现在6月、7月,仅中国南方部分地区存在冬季异常现象,且春、夏季的HmF2均值大于秋、冬季;在日变化中,NmF2和TEC的最大值主要出现在地方时(local time,LT)12:00—16:00,且峰值对应的地方时随纬度升高而向前推移。当太阳活动高年时,日落后NmF2和TEC仍保持较高水平。HmF2在中国南方地区最大值出现在LT 12:00—16:00,最小值出现在LT 05:00—07:00,北方地区HmF2的值白天普遍低于夜间。展开更多
In this paper we investigate the scattering of massless Dirac wave from several different black hole spacetimes(i.e. the Schwarzschild black hole, the RN extremal black hole, the Schwarzschild de Sitter black hole, an...In this paper we investigate the scattering of massless Dirac wave from several different black hole spacetimes(i.e. the Schwarzschild black hole, the RN extremal black hole, the Schwarzschild de Sitter black hole, and the extremal Schwarzschild de Sitter black hole) which are influenced by the cosmic string, respectively. All these cases show us that the total absorption cross sections oscillate around the geometric-optical limit and decrease with linear mass density μof the cosmic string. All of the total scattering cross sections exhibit that the main scattering angle becomes narrower for the high partial frequency wave. Due to the influence of cosmic string, the glory peak becomes wider for larger values of linear mass density μ of the cosmic string.展开更多
顶部电离层是指F2层电子密度最大值所在高度以上的电离层区域。掩星观测能够提供地面到低轨卫星轨道高度处的整个电离层电子密度剖面,对于顶部电离层的研究具有重要作用。标高是构建顶部以上电离层电子密度剖面模型的重要参数。本文使用...顶部电离层是指F2层电子密度最大值所在高度以上的电离层区域。掩星观测能够提供地面到低轨卫星轨道高度处的整个电离层电子密度剖面,对于顶部电离层的研究具有重要作用。标高是构建顶部以上电离层电子密度剖面模型的重要参数。本文使用2007—2020年的气象、电离层和气候星座观测系统(Constellation Observing System for Meteorology,Ionosphere and Climate,COSMIC)掩星观测数据,提取有效电子密度剖面数据的顶部标高,分析了其随地方时、季节、经纬度和太阳活动水平的变化特性。结果表明:顶部标高具有明显的日变化和季节变化规律,并且表现出强烈的太阳活动依赖性;顶部标高在纬度上的变化强烈依赖于地方时,同时在东西经向上表现出明显的波状结构,且这种经度波状结构在南北半球具有不同的形态;顶部标高在夏季半球具有显著的东西经向差异,南半球夏季更为明显。展开更多
We study a two-dimensional generalized Kemmer oscillator in the cosmic string spacetime with the magnetic field to better understand the contribution from gravitational field caused by topology defects,and present the...We study a two-dimensional generalized Kemmer oscillator in the cosmic string spacetime with the magnetic field to better understand the contribution from gravitational field caused by topology defects,and present the exact solutions to the generalized Kemmer equation in the cosmic string with the Morse potential and Coulomb-liked potential through using the Nikiforov-Uvarov(NU)method and biconfluent Heun equation method,respectively.Our results give the topological defect’s correction for the wave function,energy spectrum and motion equation,and show that the energy levels of the generalized Kemmer oscillator rely on the angular deficitαconnected with the linear mass density m of the cosmic string and characterized the metric’s structure in the cosmic string spacetime.展开更多
We find an azimuthal-angle dependent approximate wave like solution to second order on a warped five-dimensional manifold with a self-gravitating U(1) scalar gauge field (cosmic string) on the brane using the multiple...We find an azimuthal-angle dependent approximate wave like solution to second order on a warped five-dimensional manifold with a self-gravitating U(1) scalar gauge field (cosmic string) on the brane using the multiple-scale method. The spectrum of the several orders of approximation show maxima of the energy distribution dependent on the azimuthal-angle and the winding numbers n of the subsequent orders of scalar field. This breakup of the quantized flux quanta does not lead to instability of the asymptotic wavelike solution, due to the suppression of the n-dependency in the energy mo-mentum tensor components by the warp factor. This effect is triggered by the contribution of the five dimensional Weyl tensor on the brane. This con-tribution can be understood as dark energy and can trigger the self-acceleration of the universe without the need of a cosmological constant. There is a striking relation between the symmetry breaking of the Higgs field described by the winding number and the SO(2) breaking of the axially symmetric configuration into a discrete subgroup of rotations about 180°. The discrete sequence of non-axially symmetric deviations, cancelled by the emission of gravitational waves in order to restore the SO(2) symmetry, triggers the pressure Tzz for discrete values of the azimuthal-angle. There can be a possible relation between the recently discovered angle-preferences of polarization axes of quasars on large scales and our theoretical predicted angle-dependency and can be an evidence for the existence of cosmic strings. The discovery of the increase of polarization rate in smaller subgroups of the several large-quasar groups (LQGs), the red shift dependency and the relative orientation of the spin axes with respect to the major axes of their host LQGs, point at a fractional azimuthal structure, were also found in our cosmic string model. This peculiar discontinuous large scale structure, i.e., polarizations directions of multiples of, for example, π/2 orπ/4, can be explained by the spectrum of azimuthal-angle dependent wavelike modes without the need of conventional density perturbations in standard 4D cosmological models. Carefully com-parison of the spectrum of extremal values of the first and second order φ-dependency and the distribution of the alignment of the quasar polarizations is necessary. This can be accomplished when more observational data become available.展开更多
文摘COSMIC-2(constellation observing system for meteorology ionosphere and climate-2)作为COSMIC掩星星座的后续计划,得益于升级了支持多模GNSS信号的接收机和高增益定向波束掩星天线,其观测数据质量和数量得到显著提升。围绕掩星观测数据和反演产品的定量评估,分析COSMIC-2定轨和掩星天线的原始观测数据质量,并以欧洲中期数值天气预报中心的再分析气象资料为基准,定量评估掩星反演大气廓线产品质量。结果显示,COSMIC-2定轨天线L1频段信噪比大多在45 dB以上,其对应伪距多路径效应中误差在0.2~0.4 m之间;掩星天线观测信噪比由第一代COSMIC的不足700 v/v大幅提升至1200 v/v,且GLONASS掩星廓线和GPS掩星廓线均与气象再分析资料表现出了很好的一致性。研究结果认为,升级后的COSMIC-2掩星载荷不仅大幅增加掩星观测数量,其高增益的掩星天线设计还有效地提升了掩星观测数据质量,为大气科学研究提供了重要气象观测资料。
文摘Let F_(1)be the virtual field consisting of one element and(Q,I)a string pair.In this paper,we study the representations of string pairs over the virtual field F_(1).It is proved that an indecomposable F_(1)-representation is either a string representation or a band representation by using the coefficient quivers.It is worth noting that for a given band and a positive integer,there exists a unique band representation up to isomorphism.
文摘In this paper, in Section 1, we have described some equations and theorems concerning the Lebesgue integral and the Lebesgue measure. In Section 2, we have described the possible mathematical applications, of Lebesgue integration, in some equations concerning various sectors of Chern-Simons theory and Yang-Mills gauge theory, precisely the two dimensional quantum Yang-Mills theory. In conclusion, in Section 3, we have described also the possible mathematical connections with some sectors of String Theory and Number Theory, principally with some equations concerning the Ramanujan’s modular equations that are related to the physical vibrations of the bosonic strings and of the superstrings, some Ramanujan’s identities concerning π and the zeta strings.
基金the support by grants from the NNSF of China with Grant Nos.12275264 and 12247103。
文摘This is a writeup of lectures delivered at the Asian Pacific Introductory School on Superstring and Related Topics in Beijing(2006)and an expanded version of these lectures given at the Third Summer School on Strings,Fields and Holography in Nanjing(2023).It aims to provide both a historical and pedagogical account of developments in finding 1/2 Bogomol?nyi–Prasad–Sommerfield(BPS)extended string solitons during the early stage of the so-called second string revolution,before which these objects were thought to be unrelated to strings.Nonsupersymmetric solutions related to brane/anti brane systems or non-BPS systems are also discussed.
基金funded by the Research council of Norway,Equinor and Sekal with NFR(Grant No.308826).
文摘During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a numerical model is developed to simulate the effects of repeated loading on rock fatigue and failure.The simulation is based on an elasto-plastic constitutive model coupled with a damage mechanics approach,which allows us to examine the wellbore instability due to drill string vibrations.The model is verified with the existing data in the literature related to experiments on impact of a steel ball against a curved wall.The findings indicate that cyclic loading increases the development of plastic strain around the wellbore significantly compared to static conditions,promoting rock fatigue.Furthermore,the cyclic loading expands the radius of the yielded zone substantially,a critical factor for maintaining wellbore integrity.The proposed model can be used to evaluate the wellbore stability under repetitive loading caused by the drill string action.
基金supported by the Natural Science Foundation of Fujian Province(Grant No.2022J011130)the Research Starting Grant from Minjiang University(Grant No.30804317)。
文摘A new phenomenological model(axionic QCD string)is constructed to study the topological issues of the QCD vacuum and hadron structure.It provides an alternative way of tackling the Strong CP problem,which is different from the traditional Peccei–Quinn approach.Neither new particle nor extra symmetry is introduced,and the role of the Peccei–Quinn axion is played by a quasiparticle arising from the phase of the quark condensate,dubbed as axionic excitation.The derivative of this excitation field is decomposed into a regular part and a singular part,and the latter contains vorticity from the string configuration.A hidden gauge symmetry is revealed in this decomposition and vorticity is represented by an emergent gauge field associated with anomalies.These components,together with the anomaly-inflow mechanism,complete the effective Lagrangian description for the axionic QCD string.
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 consider a static spherically symmetric black hole(BH)embedded in a Dehnen-(1,4,0)-type dark matter(DM)halo in the presence of a cloud string.We examine and present data on how the core density of the DM halo parameter and the cloud string parameter affect BH attributes such as quasinormal modes(QNMs)and shadow cast.To do this,we first look into the effective potential of perturbation equations for three types of perturbation fields with different spins:massless scalar field,electromagnetic field and gravitational field.Then,using the sixth-order Wentzel-Kramers-Brillouin approximation,we examine QNMs of the BH disturbed by the three fields and derive quasinormal frequencies.The changes in QNM versus the core density parameter and the cloud string parameter for three disturbances are explored.We also investigate how the core density and the cloud string parameter affect the photon sphere and shadow radius.Interestingly,the study shows that the influence of Dehnen-type DM and cloud strings increases both the photon sphere and the shadow radius.Finally,we employ observational data from Sgr A^(*) and M87^(*) to set limitations on the BH parameters.
基金supported by the National Natural Science Foundation of China(52174003,52374008).
文摘The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of drill string.Due to the super slenderness ratio of drill string,strong nonlinearity implied in dynamic analysis and the complex load environment,dynamic simulation of drill string faces great challenges.At present,many simulation methods have been developed to analyze drill string dynamics,and node iteration method is one of them.The node iteration method has a unique advantage in dealing with the contact characteristics between drill string and borehole wall,but its drawback is that the calculation consumes a considerable amount of time.This paper presents a dynamic simulation method of drilling string in extra-deep well based on successive over-relaxation node iterative method(SOR node iteration method).Through theoretical analysis and numerical examples,the correctness and validity of this method were verified,and the dynamics characteristics of drill string in extra-deep wells were calculated and analyzed.The results demonstrate that,in contrast to the conventional node iteration method,the SOR node iteration method can increase the computational efficiency by 48.2%while achieving comparable results.And the whirl trajectory of the extra-deep well drill string is extremely complicated,the maximum rotational speed downhole is approximately twice the rotational speed on the ground.The dynamic torque increases rapidly at the position of the bottom stabilizer,and the lateral vibration in the middle and lower parts of drill string is relatively intense.
文摘We investigate the relationship between the magnitudes of Forbush decreases(FDs)and solar-geomagnetic characteristics using daily-averaged galactic cosmic ray(GCR)data from Inuvick(INVK)and Magadan(MGDN)neutron monitor(NM)stations to aid in counting the case of GCR flux intensity modulation.The FDs,obtained with an automated new computer software algorithm from daily-averaged GCR data from the IZMIRAN common website:http://cr0.izmiran.ru/common,at INVK(224)and MGDN(229)NM stations,from 1998 to 2002,were used in the present work.The associated solar-geomagnetic parameters of the same time range were obtained from the OMNI website.A statistical analytical method was employed to test the link between FD amplitudes and solargeomagnetic variables.We observed negative trends in FD-IMF,FD-SWS,FD-Kp,FD-SSN and FD-SI,while a positive relation was indicated in FD-Dst at both stations.All are statistically significant at a 95%confidence level.The results obtained here imply that solar emission characteristics impact the GCR flux intensity modulation.
文摘利用2006—2020年中国区域的COSMIC-1/2(constellation observing system for meteorology ionosphere and climate-1/2)IonPrf产品数据,分析了中国区域电离层时空变化特征。首先介绍新一代COSMIC-2在中国以及全球区域的数据质量状况;然后对IonPrf产品的数据质量控制和电离层特征参数提取方法进行说明;最后,以不同时间尺度统计分析了中国区域近15年电离层特征参数在一个完整太阳活动周期不同活动水平下的时空变化特征。统计结果表明,中国区域电离层变化具有与太阳活动相关的周年变化、季节变化和日变化特征;周年变化中具有明显空间分布特征,以30°N左右为界,中国南方地区峰值密度NmF2、峰值高度HmF2和电子总含量(total electron content,TEC)年均值普遍高于北方地区;在月份季节变化中,NmF2和TEC最大值一般出现在3月、10月,最小值出现在6月、7月,仅中国南方部分地区存在冬季异常现象,且春、夏季的HmF2均值大于秋、冬季;在日变化中,NmF2和TEC的最大值主要出现在地方时(local time,LT)12:00—16:00,且峰值对应的地方时随纬度升高而向前推移。当太阳活动高年时,日落后NmF2和TEC仍保持较高水平。HmF2在中国南方地区最大值出现在LT 12:00—16:00,最小值出现在LT 05:00—07:00,北方地区HmF2的值白天普遍低于夜间。
基金Supported by the National Natural Science Foundation of China under Grant No.10873004the State Key Development Program for Basic Research Program of China under Grant No.2010CB832803
文摘In this paper we investigate the scattering of massless Dirac wave from several different black hole spacetimes(i.e. the Schwarzschild black hole, the RN extremal black hole, the Schwarzschild de Sitter black hole, and the extremal Schwarzschild de Sitter black hole) which are influenced by the cosmic string, respectively. All these cases show us that the total absorption cross sections oscillate around the geometric-optical limit and decrease with linear mass density μof the cosmic string. All of the total scattering cross sections exhibit that the main scattering angle becomes narrower for the high partial frequency wave. Due to the influence of cosmic string, the glory peak becomes wider for larger values of linear mass density μ of the cosmic string.
文摘顶部电离层是指F2层电子密度最大值所在高度以上的电离层区域。掩星观测能够提供地面到低轨卫星轨道高度处的整个电离层电子密度剖面,对于顶部电离层的研究具有重要作用。标高是构建顶部以上电离层电子密度剖面模型的重要参数。本文使用2007—2020年的气象、电离层和气候星座观测系统(Constellation Observing System for Meteorology,Ionosphere and Climate,COSMIC)掩星观测数据,提取有效电子密度剖面数据的顶部标高,分析了其随地方时、季节、经纬度和太阳活动水平的变化特性。结果表明:顶部标高具有明显的日变化和季节变化规律,并且表现出强烈的太阳活动依赖性;顶部标高在纬度上的变化强烈依赖于地方时,同时在东西经向上表现出明显的波状结构,且这种经度波状结构在南北半球具有不同的形态;顶部标高在夏季半球具有显著的东西经向差异,南半球夏季更为明显。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11465006 and 11565009)。
文摘We study a two-dimensional generalized Kemmer oscillator in the cosmic string spacetime with the magnetic field to better understand the contribution from gravitational field caused by topology defects,and present the exact solutions to the generalized Kemmer equation in the cosmic string with the Morse potential and Coulomb-liked potential through using the Nikiforov-Uvarov(NU)method and biconfluent Heun equation method,respectively.Our results give the topological defect’s correction for the wave function,energy spectrum and motion equation,and show that the energy levels of the generalized Kemmer oscillator rely on the angular deficitαconnected with the linear mass density m of the cosmic string and characterized the metric’s structure in the cosmic string spacetime.
文摘We find an azimuthal-angle dependent approximate wave like solution to second order on a warped five-dimensional manifold with a self-gravitating U(1) scalar gauge field (cosmic string) on the brane using the multiple-scale method. The spectrum of the several orders of approximation show maxima of the energy distribution dependent on the azimuthal-angle and the winding numbers n of the subsequent orders of scalar field. This breakup of the quantized flux quanta does not lead to instability of the asymptotic wavelike solution, due to the suppression of the n-dependency in the energy mo-mentum tensor components by the warp factor. This effect is triggered by the contribution of the five dimensional Weyl tensor on the brane. This con-tribution can be understood as dark energy and can trigger the self-acceleration of the universe without the need of a cosmological constant. There is a striking relation between the symmetry breaking of the Higgs field described by the winding number and the SO(2) breaking of the axially symmetric configuration into a discrete subgroup of rotations about 180°. The discrete sequence of non-axially symmetric deviations, cancelled by the emission of gravitational waves in order to restore the SO(2) symmetry, triggers the pressure Tzz for discrete values of the azimuthal-angle. There can be a possible relation between the recently discovered angle-preferences of polarization axes of quasars on large scales and our theoretical predicted angle-dependency and can be an evidence for the existence of cosmic strings. The discovery of the increase of polarization rate in smaller subgroups of the several large-quasar groups (LQGs), the red shift dependency and the relative orientation of the spin axes with respect to the major axes of their host LQGs, point at a fractional azimuthal structure, were also found in our cosmic string model. This peculiar discontinuous large scale structure, i.e., polarizations directions of multiples of, for example, π/2 orπ/4, can be explained by the spectrum of azimuthal-angle dependent wavelike modes without the need of conventional density perturbations in standard 4D cosmological models. Carefully com-parison of the spectrum of extremal values of the first and second order φ-dependency and the distribution of the alignment of the quasar polarizations is necessary. This can be accomplished when more observational data become available.
