There are two kinds of definitions of perturbation of physical quantities in the framework of general relativity： one is direct, the other is geometrical. Correspondingly, there are two types of gauge transformation ...There are two kinds of definitions of perturbation of physical quantities in the framework of general relativity： one is direct, the other is geometrical. Correspondingly, there are two types of gauge transformation related with these two definitions. The passive approach is based on the property of general covariance, and the active one is through the action of Lie-derivative. Although under a proper coordinate choice, the two approaches seem to agree with each other, they are different in nature. The geometrical definition of relativistic perturbation and the active approach for gauge transformation are more rigorous in mathematics and less confusing in physical explanation. The direct definition, however, seems to be plagued with difficulties in physical meaning, and the passive approach is more awkward to use, especially for high-order gauge transformations.展开更多
We provide a new proof of Cachazo-Svrcek-Witten rules for tree-level gluonic amplitudes.As a key step,we explicitly demonstrate the cancellation of spurious poles originating from the maximally helicity violating vert...We provide a new proof of Cachazo-Svrcek-Witten rules for tree-level gluonic amplitudes.As a key step,we explicitly demonstrate the cancellation of spurious poles originating from the maximally helicity violating vertices in these rules.To achieve this,we introduce specially-defined two-off-shell-line sub-amplitudes and examine their residues at spurious poles.展开更多
基金supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,the Ministry of Educationthe Chinese Academy of Sciences under Grant No.KJCX3-SYW-N2
文摘There are two kinds of definitions of perturbation of physical quantities in the framework of general relativity： one is direct, the other is geometrical. Correspondingly, there are two types of gauge transformation related with these two definitions. The passive approach is based on the property of general covariance, and the active one is through the action of Lie-derivative. Although under a proper coordinate choice, the two approaches seem to agree with each other, they are different in nature. The geometrical definition of relativistic perturbation and the active approach for gauge transformation are more rigorous in mathematics and less confusing in physical explanation. The direct definition, however, seems to be plagued with difficulties in physical meaning, and the passive approach is more awkward to use, especially for high-order gauge transformations.
基金supported by the National Natural Science Foundation of China(Grant Nos.11975164,11935009,12047502,and 11947301)Natural Science Foundation of Tianjin(Grant No.20JCYBJC00910)supported by a fund from Hunan University of Arts and Science。
文摘We provide a new proof of Cachazo-Svrcek-Witten rules for tree-level gluonic amplitudes.As a key step,we explicitly demonstrate the cancellation of spurious poles originating from the maximally helicity violating vertices in these rules.To achieve this,we introduce specially-defined two-off-shell-line sub-amplitudes and examine their residues at spurious poles.
