Based on the phase-space path integral for a system with a regular or singular Lagrangian the generalized canonical Ward identities under the global symmetry transformation in extended phase space are deduced respecti...Based on the phase-space path integral for a system with a regular or singular Lagrangian the generalized canonical Ward identities under the global symmetry transformation in extended phase space are deduced respectively, thus the relations among Green functions can be found. The connection between canonical symmetries and conservation laws at the quantum level is established. It is pointed out that this connection in classical theories, in general, is no longer always preserved in quantum theories. The advantage of our formulation is that we do not need to carry out the integration over the canonical momenta in phase-space generating functional as usually performed. A precise discussion of quantization for a nonlinear sigma model with Hopf and Chern-Simons terms is reexamined. The property of fractional spin at quantum level has been clarified.展开更多
According to the method of path integral quantization for the canonical constrained system in Becchi-Rouet-Stora-Tyutin scheme, the supersymmetric electromagnetic interaction system was quantized. Both the Hamiltonian...According to the method of path integral quantization for the canonical constrained system in Becchi-Rouet-Stora-Tyutin scheme, the supersymmetric electromagnetic interaction system was quantized. Both the Hamiltonian of the supersymmetric electromagnetic interaction system in phase space and the quantization procedure were simplified. The BRST generator was constructed, and the BRST transforma- tions of supersymmetric fields were gotten; the effective action was calculated, and the generating functional for the Green function was achieved; also, the gauge generator was constructed, and the gauge transformation of the system was ob- tained. Finally, the Ward-Takahashi identities based on the canonical Noether theorem were calculated, and two relations between proper vertices and propaga- tors were obtained.展开更多
The operators of b→ sγ, b →sl＋l- are usually regarded as being sufficient to describe b →sγγ, b → sl＋l-T with the statement that contributions from diagrams without an effective vertex b --＊ ST to processes...The operators of b→ sγ, b →sl＋l- are usually regarded as being sufficient to describe b →sγγ, b → sl＋l-T with the statement that contributions from diagrams without an effective vertex b --＊ ST to processes b →sγγ and b →sl＋l-T are negligible. In this work we present a comprehensive analysis of the transition b→sγγ and find that 1） Effects due to off-shell quarks in vertex b → sγ on b →sγγ are large; 2） Contributions from diagrams without an effective vertex b →sγ to b →sγγ are not negligible compared with others; 3） These effects cancel each other out exactly, so the operators of b→sγ can safely be used to describe b →sγγ.展开更多
Based on the Ward-Takahashi identity at finite chemical potential and Lorentz structure analyms, we generalize the Ball-Chiu vertex to the case of nonzero chemical potential and obtain the general form of the frmionbo...Based on the Ward-Takahashi identity at finite chemical potential and Lorentz structure analyms, we generalize the Ball-Chiu vertex to the case of nonzero chemical potential and obtain the general form of the frmionboson vertex in QED at finite chemical potential.展开更多
A topological way to distinguish divergences of the Abelian axial-vector current in quantum field theory is proposed. By using the properties of the Atiyah-Singer index theorem, the nomtrivial Jacobian factor of the i...A topological way to distinguish divergences of the Abelian axial-vector current in quantum field theory is proposed. By using the properties of the Atiyah-Singer index theorem, the nomtrivial Jacobian factor of the integration measure in the path-integral formulation of the theory is connected with the topological properties of the gauge field. The singularity of the fermion current related to the topological character can be correctly examined in a gauge background.展开更多
It is shown that a novel anomaly associated with transverse Ward-Takahashi identity of axial vector current in QED is derived by using Fujikawa’s method in the path-integral formulation of quantum field theory. Also ...It is shown that a novel anomaly associated with transverse Ward-Takahashi identity of axial vector current in QED is derived by using Fujikawa’s method in the path-integral formulation of quantum field theory. Also it is verified that there is no transverse anomaly for the vector current.展开更多
基金National Natural Science Foundation of ChinaBeijing Natural Science Foundation.
文摘Based on the phase-space path integral for a system with a regular or singular Lagrangian the generalized canonical Ward identities under the global symmetry transformation in extended phase space are deduced respectively, thus the relations among Green functions can be found. The connection between canonical symmetries and conservation laws at the quantum level is established. It is pointed out that this connection in classical theories, in general, is no longer always preserved in quantum theories. The advantage of our formulation is that we do not need to carry out the integration over the canonical momenta in phase-space generating functional as usually performed. A precise discussion of quantization for a nonlinear sigma model with Hopf and Chern-Simons terms is reexamined. The property of fractional spin at quantum level has been clarified.
基金Supported by Knowledge Innovation Project of the Chinese Academy of Sciences (Grant Nos. KJCX2-SW-N02 and KJCX2-SW-N016)the National Natural Science Foundation of China (Grant Nos. 10435080 and 10575123)+1 种基金Beijing Natural Science Foundation (Grant No. 1072005)the Science and Technology Development Foundation of Beijing Municipal Education Committee (Grant No. Km200310005018)
文摘According to the method of path integral quantization for the canonical constrained system in Becchi-Rouet-Stora-Tyutin scheme, the supersymmetric electromagnetic interaction system was quantized. Both the Hamiltonian of the supersymmetric electromagnetic interaction system in phase space and the quantization procedure were simplified. The BRST generator was constructed, and the BRST transforma- tions of supersymmetric fields were gotten; the effective action was calculated, and the generating functional for the Green function was achieved; also, the gauge generator was constructed, and the gauge transformation of the system was ob- tained. Finally, the Ward-Takahashi identities based on the canonical Noether theorem were calculated, and two relations between proper vertices and propaga- tors were obtained.
基金Supported by China Postdoctoral Science Foundation (20080440292)
文摘The operators of b→ sγ, b →sl＋l- are usually regarded as being sufficient to describe b →sγγ, b → sl＋l-T with the statement that contributions from diagrams without an effective vertex b --＊ ST to processes b →sγγ and b →sl＋l-T are negligible. In this work we present a comprehensive analysis of the transition b→sγγ and find that 1） Effects due to off-shell quarks in vertex b → sγ on b →sγγ are large; 2） Contributions from diagrams without an effective vertex b →sγ to b →sγγ are not negligible compared with others; 3） These effects cancel each other out exactly, so the operators of b→sγ can safely be used to describe b →sγγ.
基金The project supported in part by National Natural Science Foundation of China under Grant Nos. 10175033, 10135030, 10575050, and 10475057 and the Research Fund for Doctoral Program of Higher Education under Grant No. 20030284009
文摘Based on the Ward-Takahashi identity at finite chemical potential and Lorentz structure analyms, we generalize the Ball-Chiu vertex to the case of nonzero chemical potential and obtain the general form of the frmionboson vertex in QED at finite chemical potential.
文摘A topological way to distinguish divergences of the Abelian axial-vector current in quantum field theory is proposed. By using the properties of the Atiyah-Singer index theorem, the nomtrivial Jacobian factor of the integration measure in the path-integral formulation of the theory is connected with the topological properties of the gauge field. The singularity of the fermion current related to the topological character can be correctly examined in a gauge background.
文摘It is shown that a novel anomaly associated with transverse Ward-Takahashi identity of axial vector current in QED is derived by using Fujikawa’s method in the path-integral formulation of quantum field theory. Also it is verified that there is no transverse anomaly for the vector current.
