# Angular momentum conservation law in light-front quantum field theory and extended conformal symmetry of Abelian gauge theory in D ≠ 4

## Abstract/Contents

- Abstract
- This thesis investigates two independent aspects of spacetime symmetries. The first part of my thesis is about the angular momentum conservation law in light-front quantum field theory. We prove the light-front Poincare invariance of the angular momentum conservation law and the helicity sum rule for relativistic composite systems. We show that the light-front wavefunction (LFWF), which describes the internal structure of a bound state, is in fact frame independent, in contrast to instant form wavefunctions. In particular, we demonstrate that j3, the intrinsic angular momentum projected onto the light-front direction, is independent of the bound state's 4-momentum and the observer's Lorentz frame. The frame independence of j3 is a feature unique to the front form. The angular momentum conservation law leads directly to a nonperturbative proof of the constraint A(0)=1 and the vanishing of the anomalous gravitomagetic moment B(0)=0. Based on the conservation of angular momentum, we derive a selection rule for orbital angular momentum which can be used to eliminate certain interaction vertices in QED and QCD. We also generalize the selection rule to any renormalizable theory and show that there exists an upper bound on the change of orbital angular momentum in scattering processes at any fixed order in perturbation theory. The second part of my thesis investigates an extended conformal symmetry for Abelian gauge theory in general dimensions. Maxwell theory in d \neq 4 spacetime dimensions is an example of a scale-invariant theory which does not possess conformal symmetry -- the special conformal transformation (SCT) explicitly breaks the gauge invariance of the theory. We construct a non-local gauge-invariant extension of the SCT, which is compatible with the BRST formalism and defines a new symmetry of the physical Hilbert space of the Maxwell theory for any dimension d \geqslant 3. We prove the invariance of Maxwell theory in d \geqslant 3 by explicitly showing that the gauge-invariant two-point correlation functions, the action, and the classical equation of motion are unchanged under such a transformation.

## Description

Type of resource | text |
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Form | electronic resource; remote; computer; online resource |

Extent | 1 online resource. |

Place | California |

Place | [Stanford, California] |

Publisher | [Stanford University] |

Copyright date | 2018; ©2018 |

Publication date | 2018; 2018 |

Issuance | monographic |

Language | English |

## Creators/Contributors

Author | Chiu, Yu-Ju | |
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Degree supervisor | Brodsky, S | |

Thesis advisor | Brodsky, S | |

Thesis advisor | Cabrera, Blas | |

Thesis advisor | Peskin, Michael Edward, 1951- | |

Degree committee member | Cabrera, Blas | |

Degree committee member | Peskin, Michael Edward, 1951- | |

Associated with | Stanford University, Department of Physics. |

## Subjects

Genre | Theses |
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Genre | Text |

## Bibliographic information

Statement of responsibility | Kelly Yu-Ju Chiu. |
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Note | Submitted to the Department of Physics. |

Thesis | Thesis Ph.D. Stanford University 2018. |

Location | electronic resource |

## Access conditions

- Copyright
- © 2018 by Yu-Ju Chiu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).

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