Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium.Recent experimental progress is much from optical,cold-atomic,and classical platforms due to the vast tunability and c...Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium.Recent experimental progress is much from optical,cold-atomic,and classical platforms due to the vast tunability and clear identification of observables.However,their counterpart in solid-state electronic systems in equilibrium remains unmasked although highly desired,where a variety of materials are available,calculations are solidly founded,and accurate spectroscopic techniques can be applied.We demonstrate that,in the surface state of a topological insulator with spin-dependent relaxation due to magnetic impurities,highly nontrivial topological soliton spin textures appear in momentum space.Such spin-channel phenomena are delicately related to the type of non-Hermiticity and correctly reveal the most robust non-Hermitian features detectable spectroscopically.Moreover,the distinct topological soliton objects can be deformed to each other,mediated by topological transitions driven by tuning across a critical direction of doped magnetism.These results not only open a solid-state avenue to exotic spin patterns via spin-and angle-resolved photoemission spectroscopy,but also inspire non-Hermitian dissipation engineering of spins in solids.展开更多
随着云计算应用范围的扩展,人们对云计算在安全性、可靠性、可用性等方面的担忧与日俱增。云计算服务商承诺提供的服务满足服务水平协议,主要包括性能和可用性。但是,因可用性的内在复杂性而缺乏定量评估手段,对于云计算系统用户而言更...随着云计算应用范围的扩展,人们对云计算在安全性、可靠性、可用性等方面的担忧与日俱增。云计算服务商承诺提供的服务满足服务水平协议,主要包括性能和可用性。但是,因可用性的内在复杂性而缺乏定量评估手段,对于云计算系统用户而言更是如此。为此,提出面向最终用户和面向云计算服务提供商的云计算系统可用性评估方法,这两种方法都采用可用性的定义建立模型,并且采用虚拟机的启动时间代替平均故障修复时间(Mean Time To Repair,MTTR)。第一种方法的平均失效前时间(Mean Time To Failure,MTTF)采用云计算服务提供商提供的参数;第二种方法通过统计得到虚拟机的MTTF,并计算云计算系统之上的集群可用性。由于难以对后者进行实验验证,因此只对第一种方法进行验证,通过实验测量公有云和私有云提供的虚拟机的启动时间,结合云计算服务提供商提供的MTTF,计算了两种不同云平台服务的可用性,该方法方便用户快速计算可用性,为用户选择不同的云服务提供建议,并且可以判断云计算服务提供商的承诺是否达到标准以及是否可以将一些关键行业应用服务迁移至云平台。展开更多
基金supported by JSPS KAKENHI(18H03676)JST CREST(JPMJCR1874)supported by RIKEN Special Postdoctoral Researcher Program。
文摘Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium.Recent experimental progress is much from optical,cold-atomic,and classical platforms due to the vast tunability and clear identification of observables.However,their counterpart in solid-state electronic systems in equilibrium remains unmasked although highly desired,where a variety of materials are available,calculations are solidly founded,and accurate spectroscopic techniques can be applied.We demonstrate that,in the surface state of a topological insulator with spin-dependent relaxation due to magnetic impurities,highly nontrivial topological soliton spin textures appear in momentum space.Such spin-channel phenomena are delicately related to the type of non-Hermiticity and correctly reveal the most robust non-Hermitian features detectable spectroscopically.Moreover,the distinct topological soliton objects can be deformed to each other,mediated by topological transitions driven by tuning across a critical direction of doped magnetism.These results not only open a solid-state avenue to exotic spin patterns via spin-and angle-resolved photoemission spectroscopy,but also inspire non-Hermitian dissipation engineering of spins in solids.
文摘随着云计算应用范围的扩展,人们对云计算在安全性、可靠性、可用性等方面的担忧与日俱增。云计算服务商承诺提供的服务满足服务水平协议,主要包括性能和可用性。但是,因可用性的内在复杂性而缺乏定量评估手段,对于云计算系统用户而言更是如此。为此,提出面向最终用户和面向云计算服务提供商的云计算系统可用性评估方法,这两种方法都采用可用性的定义建立模型,并且采用虚拟机的启动时间代替平均故障修复时间(Mean Time To Repair,MTTR)。第一种方法的平均失效前时间(Mean Time To Failure,MTTF)采用云计算服务提供商提供的参数;第二种方法通过统计得到虚拟机的MTTF,并计算云计算系统之上的集群可用性。由于难以对后者进行实验验证,因此只对第一种方法进行验证,通过实验测量公有云和私有云提供的虚拟机的启动时间,结合云计算服务提供商提供的MTTF,计算了两种不同云平台服务的可用性,该方法方便用户快速计算可用性,为用户选择不同的云服务提供建议,并且可以判断云计算服务提供商的承诺是否达到标准以及是否可以将一些关键行业应用服务迁移至云平台。
