Topological phases featuring non-Abelian charges have garnered significant attention in recent years.In parallel,the study of multiband exceptional topology in non-Hermitian systems has emerged as a prominent research...Topological phases featuring non-Abelian charges have garnered significant attention in recent years.In parallel,the study of multiband exceptional topology in non-Hermitian systems has emerged as a prominent research direction.In this study,we investigate a parity-time(PT)symmetric Hamiltonian,which hosts both conventional non-Abelian topological phases(NATPs)and hybrid phases.We propose an experimental scheme using spin-1 atoms with spin-orbit coupling trapped in two-dimensional(2D)lattices.Before adding a non-Hermitian term,we find the emergence of distinct topological phases mixed by two NATPs and establish their connection with NATPs theory.When a non-Hermitian term that preserves PT symmetry protection was introduced,stable second-order exceptional rings and third-order exceptional points emerge and they drive the edge states to manifest as discontinuous Fermi arcs in the surface Brillouin zone.However,with the variation of the non-Hermitian term,it is rather intriguing that two types of exceptional rings here transition from being internally tangent to externally tangent,transforming into a new topological phase equivalent to the Hermitian case.This research provides deeper insights into the nature of NATPs and the topological implications of exceptional structures,contributing to the field of topological physics.展开更多
We study the exceptional-point(EP) structure and the associated quantum dynamics in a system consisting of a non-Hermitian qubit and a Hermitian qubit. We find that the system possesses two sets of EPs, which divide t...We study the exceptional-point(EP) structure and the associated quantum dynamics in a system consisting of a non-Hermitian qubit and a Hermitian qubit. We find that the system possesses two sets of EPs, which divide the systemparameter space into PT-symmetry unbroken, partially broken and fully broken regimes, each with distinct quantumdynamics characteristics. Particularly, in the partially broken regime, while the PT-symmetry is generally broken in the whole four-dimensional Hilbert space, it is preserved in a two-dimensional subspace such that the quantum dynamics in the subspace are similar to those in the PT-symmetry unbroken regime. In addition, we reveal that the competition between the inter-qubit coupling and the intra-qubit driving gives rise to a complex pattern in the EP variation with system parameters.展开更多
Meteorological satellite ground application system resources are limited. Abnormal satellite missions often lead to hopple of system resources. In order to analyze the problem, this paper presents an anomaly analysis ...Meteorological satellite ground application system resources are limited. Abnormal satellite missions often lead to hopple of system resources. In order to analyze the problem, this paper presents an anomaly analysis method for meteorological satellite ground system based on resource bottleneck. Through the CPU, memory and I/O, several types of resources in-depth were analyzed to find the bottleneck caused by the problem, thus providing recommendations for application optimization. Experimental analysis shows that the proposed method can reasonably analyze the resource bottleneck of CPU, memory and I/O, and draw a good conclusion. To solve the meteorological satellite application system application anomaly caused by the bottleneck of the problem, the application of optimization to a certain extent plays a positive role.展开更多
In this paper, we investigate the effect of exceptional points(EPs) on the violation of Leggett–Garg inequality(LGI) and no-signaling-in-time(NSIT) conditions and compare the different effects between the Hamiltonian...In this paper, we investigate the effect of exceptional points(EPs) on the violation of Leggett–Garg inequality(LGI) and no-signaling-in-time(NSIT) conditions and compare the different effects between the Hamiltonian EP(HEP) and Liouvillian EP(LEP) on those violations. We consider an open system consisting of two coupled qubits and each qubit is contacted with a thermal bath at a different temperature. In the case of omitting quantum jumps, we find that the system exhibits a second-order HEP, which separates the parameter space into an overdamped regime and an underdamped regime. In this situation, the LGI and NSIT conditions can be violated in both regimes and not violated at the HEP. In the case of without omitting quantum jumps, we find that the system exhibits a third-order LEP, which also separates the parameter space into an overdamped regime and an underdamped regime. In this situation, the LGI can only be violated in the underdamped regime with large coupling strength between the qubits.Conversely, the NSIT conditions can be violated in both regimes, as well as at the LEP, except in the overdamped regime with small coupling strength between the qubits. Comparing the violations of the LGI and NSIT conditions with HEP and LEP, we find that the quantum jumps would reduce the generation of coherence, enhance the decoherence, and lead to narrower parameter regimes that the LGI and NSIT conditions can be violated. Furthermore, in both cases,the NSIT conditions can be violated in a wider parameter regime than the LGI.展开更多
Developing chemically complex intermetallic alloys(CCIMAs)is considered an effective strategy for overcoming the serious brittleness of conventional intermetallic alloys,especially under a high stress level.However,mo...Developing chemically complex intermetallic alloys(CCIMAs)is considered an effective strategy for overcoming the serious brittleness of conventional intermetallic alloys,especially under a high stress level.However,most CCIMAs still struggle to achieve yield strengths exceeding gigapascals,limiting their use as reliable structural materials in many engineering fields.展开更多
To solve the problems that the exception handling code is hard to test and maintain and that it affects the robustness and reliability of software, a method for evaluating the exception handling of programs is present...To solve the problems that the exception handling code is hard to test and maintain and that it affects the robustness and reliability of software, a method for evaluating the exception handling of programs is presented. The exception propagation graph （EPG） that describes the large programs with exception handling constructs is proposed by simplifying the control flow graph and it is applied to a case to verify its validity. According to the EPG, the exception handling code that never executes is identified; the points that are the most critical to controlling exception propagation are found; and the irrational exception handling code is corrected. The constructing algorithm for the EPG is given; thus, this provides a basis for automatically constructing the EPG and automatically correcting the irrational exception handling code.展开更多
美国微软开发的VB.NET2005可视化程序设计语言中,有一个DivideByZeroException类,它是当程序中有整数除法运算而除数为零时发生的异常,这种异常通过"Catch e As DivideByZeroException"语句来捕捉,捕捉到后根据相应的容错处...美国微软开发的VB.NET2005可视化程序设计语言中,有一个DivideByZeroException类,它是当程序中有整数除法运算而除数为零时发生的异常,这种异常通过"Catch e As DivideByZeroException"语句来捕捉,捕捉到后根据相应的容错处理语句继续执行。但在教学实践和实际编程中发现,在整数除法运算中发生除数为零的情况时,DivideByZeroException类异常并不能发生,这反映了微软开发的VB.NET2005程序设计语言中的一个漏洞。对这个问题进行了分析,并提出了弥补该漏洞的解决方案。展开更多
Elastic wave absorption at subwavelength scale is of significance in many engineering applications.Non-Hermitian metamaterials show the ability in high-efficiency wave absorption.However,the single functionality of me...Elastic wave absorption at subwavelength scale is of significance in many engineering applications.Non-Hermitian metamaterials show the ability in high-efficiency wave absorption.However,the single functionality of metamaterials is an important limitation on their practical applications for lack of tunability and reconfigurability.Here,we propose a tunable and reconfigurable non-Hermitian piezoelectric metamaterial bar,in which piezoelectric bars connect with resonant circuits,to achieve asymmetric unidirectional perfect absorption(UPA)and symmetric bidirectional perfect absorption(PA)at low frequencies.The two functions can be arbitrarily switched by rearranging shunted circuits.Based on the reverberation-ray matrix(RRM)method,an approach is provided to achieve UPA by setting an exceptional point(EP)in the coupled resonant bandgap.By using the transfer matrix method(TMM)and the finite element method(FEM),it is observed that a non-Hermitian pseudo-band forms between two resonant bandgaps,and the EP appears at the bottom of the pseudo-band.In addition,the genetic algorithm is used to accurately and efficiently design the shunted circuits for desired low-frequency UPA and PA.The present work may provide new strategies for vibration suppression and guided waves manipulation in wide potential applications.展开更多
The notion of “exceptional family of elements (EFE)” plays a very important role in solving complementarity prob- lems. It has been applied in finite dimensional spaces and Hilbert spaces by many authors. In this pa...The notion of “exceptional family of elements (EFE)” plays a very important role in solving complementarity prob- lems. It has been applied in finite dimensional spaces and Hilbert spaces by many authors. In this paper, by using the generalized projection defined by Alber, we extend this notion from Hilbert spaces to uniformly smooth and uniformly convex Banach spaces, and apply this extension to the study of nonlinear complementarity problems in Banach spaces.展开更多
The present note is concerned with two connected and highly important fundamental questions of physics and cosmology, namely if E8E8 Lie symmetry group describes the universe and where cosmic dark energy comes from. F...The present note is concerned with two connected and highly important fundamental questions of physics and cosmology, namely if E8E8 Lie symmetry group describes the universe and where cosmic dark energy comes from. Furthermore, we reason following Wheeler, Hartle and Hawking that since the boundary of a boundary is an empty set which models the quantum wave of the cosmos, then it follows that dark energy is a fundamental physical phenomenon associated with the boundary of the holographic boundary. This leads directly to a clopen universe which is its own Penrose tiling-like multiverse with energy density in full agreement with COBE, WMAP and Type 1a supernova cosmic measurements.展开更多
We demonstrate the possibility of dual-band unidirectional reflectionlessness in a non-Hermitian quantum system composed of a plasmonic waveguide and two end-coupled plasmonic cavities(PCs).Our scheme exhibits dual-ba...We demonstrate the possibility of dual-band unidirectional reflectionlessness in a non-Hermitian quantum system composed of a plasmonic waveguide and two end-coupled plasmonic cavities(PCs).Our scheme exhibits dual-band unidirectional reflectionlessness can be obtained at exceptional points by properly adjusting the coupling strength between two PCs,the ratio of decay rates of two PCs,and the ratio of plasmonic cavity-waveguide coupling strengths.As a valuable feature,the quality factor reaches to~175.4 in forward direction,while the backward quality factor is close to~188.2.展开更多
Open physical systems described by the non-Hermitian Hamiltonian with parity-time-reversal(PT)symmetry show peculiar phenomena,such as the presence of an exceptional point(EP)at which the PT symmetry is broken and two...Open physical systems described by the non-Hermitian Hamiltonian with parity-time-reversal(PT)symmetry show peculiar phenomena,such as the presence of an exceptional point(EP)at which the PT symmetry is broken and two resonant modes of the Hamiltonian become degenerate.Near the EP,the system could be more sensitive to external perturbations and this may lead to enhanced sensing.In this paper,we present experimental results on the observation of PT symmetry broken transition and the EP using a tunable superconducting qubit.The quantum system of investigation is formed by the two levels of the qubit and the energy loss of the system to the environment is controlled by a method of parametric modulation of the qubit frequency.This method is simple with no requirements for additional elements or qubit device modifications.We believe it can be easily implemented on multi-qubit devices that would be suitable for further exploration of non-Hermitian physics in more complex and diverse systems.展开更多
Objective The putative coronatean Punctatus flourished at the beginning of the Cambrian explosion, and is significant in the exploration of the origin and evolution of early life. Liu Yunhuan established a new specie...Objective The putative coronatean Punctatus flourished at the beginning of the Cambrian explosion, and is significant in the exploration of the origin and evolution of early life. Liu Yunhuan established a new species： Punctatus triangulicostalis Liu, 2006. Two questions remain： how was the special body plan of P. triangulicostalis formed？ How does P. triangulicostalis transform from embryo to the long cylindrical mature individual？ Although the study of Steiner et al. in 2004 involved the above questions, they did not explain them clearly due to the lack of fossil materials at that time. This article aims to consider the above questions based on new information from several rare specimens.展开更多
Featured by its uniqueness and historic significance, American exceptionalism plays an indispensable role in shaping the American political,especially the foreign policies, as well as social lives. To understand the o...Featured by its uniqueness and historic significance, American exceptionalism plays an indispensable role in shaping the American political,especially the foreign policies, as well as social lives. To understand the origins of American exceptionalism, people must look into its national values-Puritanism, individualism and political system.展开更多
It is found that when the parity–time symmetry phenomenon is introduced into the resonant optical gyro system and it works near the exceptional point,the sensitivity can in theory be significantly amplified at low an...It is found that when the parity–time symmetry phenomenon is introduced into the resonant optical gyro system and it works near the exceptional point,the sensitivity can in theory be significantly amplified at low angular rate.However,in fact,the exceptional point is easily disturbed by external environmental variables,which means that it depends on harsh experimental environment and strong control ability,so it is difficult to move towards practical application.Here,we propose a new angular rate sensor structure based on exceptional surface,which has the advantages of high sensitivity and high robustness.The system consists of two fiber-optic ring resonators and two optical loop mirrors,and one of the resonators contains a variable ratio coupler and a variable optical attenuator.We theoretically analyze the system response,and the effects of phase and coupling ratio on the system response.Finally,compared with the conventional resonant gyro,the sensitivity of this exceptional surface angular rate sensor can be improved by about 300 times at low speed.In addition,by changing the loss coefficient in the ring resonator,we can achieve a wide range of 600 rad/s.This scheme provides a new approach for the development of ultra-high sensitivity and wide range angular rate sensors in the future.展开更多
In this paper, by means of the definition of Borel exceptional value method, another exceptional value of meromorphic function which is a T exceptional value is defined by linking the concept of T direction. And we co...In this paper, by means of the definition of Borel exceptional value method, another exceptional value of meromorphic function which is a T exceptional value is defined by linking the concept of T direction. And we construct a meromorphic function with zero as Borel exceptional value, but not as T exceptional value; and another meromorphic function with zero as T exceptional value, but not as Borel exceptional value.展开更多
We propose a quasi-one-dimensional non-Hermitian Creutz ladder with an entirely flat spectrum by introducing alternating gain and loss components while maintaining inversion symmetry.Destructive interference generates...We propose a quasi-one-dimensional non-Hermitian Creutz ladder with an entirely flat spectrum by introducing alternating gain and loss components while maintaining inversion symmetry.Destructive interference generates a flat spectrum at the exceptional point,where the Creutz ladder maintains coalesced and degenerate eigenvalues with compact localized states distributed in a single plaquette.All excitations are completely confined within the localization area,unaffected by gain and loss.Single-site excitations exhibit nonunitary dynamics with intensities increasing due to level coalescence,while multiple-site excitations may display oscillating or constant intensities at the exceptional point.These results provide insights into the fascinating dynamics of non-Hermitian localization,where level coalescence and degeneracy coexist at the exceptional point.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12274473 and 12135018).
文摘Topological phases featuring non-Abelian charges have garnered significant attention in recent years.In parallel,the study of multiband exceptional topology in non-Hermitian systems has emerged as a prominent research direction.In this study,we investigate a parity-time(PT)symmetric Hamiltonian,which hosts both conventional non-Abelian topological phases(NATPs)and hybrid phases.We propose an experimental scheme using spin-1 atoms with spin-orbit coupling trapped in two-dimensional(2D)lattices.Before adding a non-Hermitian term,we find the emergence of distinct topological phases mixed by two NATPs and establish their connection with NATPs theory.When a non-Hermitian term that preserves PT symmetry protection was introduced,stable second-order exceptional rings and third-order exceptional points emerge and they drive the edge states to manifest as discontinuous Fermi arcs in the surface Brillouin zone.However,with the variation of the non-Hermitian term,it is rather intriguing that two types of exceptional rings here transition from being internally tangent to externally tangent,transforming into a new topological phase equivalent to the Hermitian case.This research provides deeper insights into the nature of NATPs and the topological implications of exceptional structures,contributing to the field of topological physics.
基金partly funded by the Natural Science Foundation of Shandong Province of China (Grant Nos. ZR2021MA091 and ZR2018MA044)Introduction and Cultivation Plan of Youth Innovation Talents for Universities of Shandong Province (Research and Innovation Team on Materials Modification and Optoelectronic Devices at extreme conditions)。
文摘We study the exceptional-point(EP) structure and the associated quantum dynamics in a system consisting of a non-Hermitian qubit and a Hermitian qubit. We find that the system possesses two sets of EPs, which divide the systemparameter space into PT-symmetry unbroken, partially broken and fully broken regimes, each with distinct quantumdynamics characteristics. Particularly, in the partially broken regime, while the PT-symmetry is generally broken in the whole four-dimensional Hilbert space, it is preserved in a two-dimensional subspace such that the quantum dynamics in the subspace are similar to those in the PT-symmetry unbroken regime. In addition, we reveal that the competition between the inter-qubit coupling and the intra-qubit driving gives rise to a complex pattern in the EP variation with system parameters.
文摘Meteorological satellite ground application system resources are limited. Abnormal satellite missions often lead to hopple of system resources. In order to analyze the problem, this paper presents an anomaly analysis method for meteorological satellite ground system based on resource bottleneck. Through the CPU, memory and I/O, several types of resources in-depth were analyzed to find the bottleneck caused by the problem, thus providing recommendations for application optimization. Experimental analysis shows that the proposed method can reasonably analyze the resource bottleneck of CPU, memory and I/O, and draw a good conclusion. To solve the meteorological satellite application system application anomaly caused by the bottleneck of the problem, the application of optimization to a certain extent plays a positive role.
基金financially supported by the National Natural Science Foundation of China (Grants Nos. 11775019 and 11875086)。
文摘In this paper, we investigate the effect of exceptional points(EPs) on the violation of Leggett–Garg inequality(LGI) and no-signaling-in-time(NSIT) conditions and compare the different effects between the Hamiltonian EP(HEP) and Liouvillian EP(LEP) on those violations. We consider an open system consisting of two coupled qubits and each qubit is contacted with a thermal bath at a different temperature. In the case of omitting quantum jumps, we find that the system exhibits a second-order HEP, which separates the parameter space into an overdamped regime and an underdamped regime. In this situation, the LGI and NSIT conditions can be violated in both regimes and not violated at the HEP. In the case of without omitting quantum jumps, we find that the system exhibits a third-order LEP, which also separates the parameter space into an overdamped regime and an underdamped regime. In this situation, the LGI can only be violated in the underdamped regime with large coupling strength between the qubits.Conversely, the NSIT conditions can be violated in both regimes, as well as at the LEP, except in the overdamped regime with small coupling strength between the qubits. Comparing the violations of the LGI and NSIT conditions with HEP and LEP, we find that the quantum jumps would reduce the generation of coherence, enhance the decoherence, and lead to narrower parameter regimes that the LGI and NSIT conditions can be violated. Furthermore, in both cases,the NSIT conditions can be violated in a wider parameter regime than the LGI.
基金financially supported by the National Natural Science Foundation of China(Nos.52222112,52101151 and 52101135)Hong Kong Research Grant Council(RGC)(No.C1020-21G)+1 种基金Shenzhen Science and Technology Program(No.RCBS20210609103202012)APT research was conducted at the Inter-University 3D APT Unit of City University of Hong Kong(CityU),which is supported by the CityU grant 9360161
文摘Developing chemically complex intermetallic alloys(CCIMAs)is considered an effective strategy for overcoming the serious brittleness of conventional intermetallic alloys,especially under a high stress level.However,most CCIMAs still struggle to achieve yield strengths exceeding gigapascals,limiting their use as reliable structural materials in many engineering fields.
基金The National Natural Science Foundation of China(No60503020)the National Basic Research Program of China (973Program) (No2002CB312000)+1 种基金the Natural Science Foundation of Jiangsu Province (NoBK2006094)the Science Research Foundation of China University of Mining and Technology
文摘To solve the problems that the exception handling code is hard to test and maintain and that it affects the robustness and reliability of software, a method for evaluating the exception handling of programs is presented. The exception propagation graph （EPG） that describes the large programs with exception handling constructs is proposed by simplifying the control flow graph and it is applied to a case to verify its validity. According to the EPG, the exception handling code that never executes is identified; the points that are the most critical to controlling exception propagation are found; and the irrational exception handling code is corrected. The constructing algorithm for the EPG is given; thus, this provides a basis for automatically constructing the EPG and automatically correcting the irrational exception handling code.
文摘美国微软开发的VB.NET2005可视化程序设计语言中,有一个DivideByZeroException类,它是当程序中有整数除法运算而除数为零时发生的异常,这种异常通过"Catch e As DivideByZeroException"语句来捕捉,捕捉到后根据相应的容错处理语句继续执行。但在教学实践和实际编程中发现,在整数除法运算中发生除数为零的情况时,DivideByZeroException类异常并不能发生,这反映了微软开发的VB.NET2005程序设计语言中的一个漏洞。对这个问题进行了分析,并提出了弥补该漏洞的解决方案。
基金the National Natural Science Foundation of China(Nos.11991033 and 11890681)。
文摘Elastic wave absorption at subwavelength scale is of significance in many engineering applications.Non-Hermitian metamaterials show the ability in high-efficiency wave absorption.However,the single functionality of metamaterials is an important limitation on their practical applications for lack of tunability and reconfigurability.Here,we propose a tunable and reconfigurable non-Hermitian piezoelectric metamaterial bar,in which piezoelectric bars connect with resonant circuits,to achieve asymmetric unidirectional perfect absorption(UPA)and symmetric bidirectional perfect absorption(PA)at low frequencies.The two functions can be arbitrarily switched by rearranging shunted circuits.Based on the reverberation-ray matrix(RRM)method,an approach is provided to achieve UPA by setting an exceptional point(EP)in the coupled resonant bandgap.By using the transfer matrix method(TMM)and the finite element method(FEM),it is observed that a non-Hermitian pseudo-band forms between two resonant bandgaps,and the EP appears at the bottom of the pseudo-band.In addition,the genetic algorithm is used to accurately and efficiently design the shunted circuits for desired low-frequency UPA and PA.The present work may provide new strategies for vibration suppression and guided waves manipulation in wide potential applications.
文摘The notion of “exceptional family of elements (EFE)” plays a very important role in solving complementarity prob- lems. It has been applied in finite dimensional spaces and Hilbert spaces by many authors. In this paper, by using the generalized projection defined by Alber, we extend this notion from Hilbert spaces to uniformly smooth and uniformly convex Banach spaces, and apply this extension to the study of nonlinear complementarity problems in Banach spaces.
文摘The present note is concerned with two connected and highly important fundamental questions of physics and cosmology, namely if E8E8 Lie symmetry group describes the universe and where cosmic dark energy comes from. Furthermore, we reason following Wheeler, Hartle and Hawking that since the boundary of a boundary is an empty set which models the quantum wave of the cosmos, then it follows that dark energy is a fundamental physical phenomenon associated with the boundary of the holographic boundary. This leads directly to a clopen universe which is its own Penrose tiling-like multiverse with energy density in full agreement with COBE, WMAP and Type 1a supernova cosmic measurements.
基金supported by the National Natural Science Foundation of China(Grant Nos.12064045,11364044 and 11864043)the Science and Technology Development Foundation of Jilin Province(Grant No.20180101342JC)Science and Technology Research Project of Education Department of Jilin Province(Grant No.JJKH20200509KJ).
文摘We demonstrate the possibility of dual-band unidirectional reflectionlessness in a non-Hermitian quantum system composed of a plasmonic waveguide and two end-coupled plasmonic cavities(PCs).Our scheme exhibits dual-band unidirectional reflectionlessness can be obtained at exceptional points by properly adjusting the coupling strength between two PCs,the ratio of decay rates of two PCs,and the ratio of plasmonic cavity-waveguide coupling strengths.As a valuable feature,the quality factor reaches to~175.4 in forward direction,while the backward quality factor is close to~188.2.
基金supported by the State Key Development Program for Basic Research of China(Grant Nos.2017YFA0304300 and 2016YFA0300600)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0303030001)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000).
文摘Open physical systems described by the non-Hermitian Hamiltonian with parity-time-reversal(PT)symmetry show peculiar phenomena,such as the presence of an exceptional point(EP)at which the PT symmetry is broken and two resonant modes of the Hamiltonian become degenerate.Near the EP,the system could be more sensitive to external perturbations and this may lead to enhanced sensing.In this paper,we present experimental results on the observation of PT symmetry broken transition and the EP using a tunable superconducting qubit.The quantum system of investigation is formed by the two levels of the qubit and the energy loss of the system to the environment is controlled by a method of parametric modulation of the qubit frequency.This method is simple with no requirements for additional elements or qubit device modifications.We believe it can be easily implemented on multi-qubit devices that would be suitable for further exploration of non-Hermitian physics in more complex and diverse systems.
基金supported by the National Natural Science Foundation of China (grant No.41572009)the State Key Laboratory of Palaeobiology and Stratigraphy (grant No.173121)the College Students’ Training Program of Chang’an University (201610710047, 201710710062, 201710710063, 201710710240)
文摘Objective The putative coronatean Punctatus flourished at the beginning of the Cambrian explosion, and is significant in the exploration of the origin and evolution of early life. Liu Yunhuan established a new species： Punctatus triangulicostalis Liu, 2006. Two questions remain： how was the special body plan of P. triangulicostalis formed？ How does P. triangulicostalis transform from embryo to the long cylindrical mature individual？ Although the study of Steiner et al. in 2004 involved the above questions, they did not explain them clearly due to the lack of fossil materials at that time. This article aims to consider the above questions based on new information from several rare specimens.
文摘Featured by its uniqueness and historic significance, American exceptionalism plays an indispensable role in shaping the American political,especially the foreign policies, as well as social lives. To understand the origins of American exceptionalism, people must look into its national values-Puritanism, individualism and political system.
基金supported in part by the National Natural Science Foundation of China (Grant Nos.62273314,U21A20141,and 51821003)Fundamental Research Program of Shanxi Province (Grant No.202303021224008)Shanxi Province Key Laboratory of Quantum Sensing and Precision Measure-ment (Grant No.201905D121001).
文摘It is found that when the parity–time symmetry phenomenon is introduced into the resonant optical gyro system and it works near the exceptional point,the sensitivity can in theory be significantly amplified at low angular rate.However,in fact,the exceptional point is easily disturbed by external environmental variables,which means that it depends on harsh experimental environment and strong control ability,so it is difficult to move towards practical application.Here,we propose a new angular rate sensor structure based on exceptional surface,which has the advantages of high sensitivity and high robustness.The system consists of two fiber-optic ring resonators and two optical loop mirrors,and one of the resonators contains a variable ratio coupler and a variable optical attenuator.We theoretically analyze the system response,and the effects of phase and coupling ratio on the system response.Finally,compared with the conventional resonant gyro,the sensitivity of this exceptional surface angular rate sensor can be improved by about 300 times at low speed.In addition,by changing the loss coefficient in the ring resonator,we can achieve a wide range of 600 rad/s.This scheme provides a new approach for the development of ultra-high sensitivity and wide range angular rate sensors in the future.
基金supported by the Natural Science Foundation of China(10161006)
文摘In this paper, by means of the definition of Borel exceptional value method, another exceptional value of meromorphic function which is a T exceptional value is defined by linking the concept of T direction. And we construct a meromorphic function with zero as Borel exceptional value, but not as T exceptional value; and another meromorphic function with zero as T exceptional value, but not as Borel exceptional value.
基金supported by the National Natural Science Foundation of China(Grant Nos.12222504 and 11975128).
文摘We propose a quasi-one-dimensional non-Hermitian Creutz ladder with an entirely flat spectrum by introducing alternating gain and loss components while maintaining inversion symmetry.Destructive interference generates a flat spectrum at the exceptional point,where the Creutz ladder maintains coalesced and degenerate eigenvalues with compact localized states distributed in a single plaquette.All excitations are completely confined within the localization area,unaffected by gain and loss.Single-site excitations exhibit nonunitary dynamics with intensities increasing due to level coalescence,while multiple-site excitations may display oscillating or constant intensities at the exceptional point.These results provide insights into the fascinating dynamics of non-Hermitian localization,where level coalescence and degeneracy coexist at the exceptional point.
