More on difference between angular momentum and pseudo-angular momentum

We extend the discussion on the difference between angular momentum and pseudo-angular momentum in field theory. We show that the often quoted expressions in [Phys.Rev.B 103, L100409 (2021)] only apply to a non-linear system, and derive the correct rotation symmetry and the corresponding angular mom...

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Bibliographic Details
Published inarXiv.org
Main Authors Dai, Qi, Zi-Wei, Chen, Bang-Hui, Hua, Xiang-Song, Chen
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 26.08.2023
Subjects
Angular momentum
Elastic systems
Elastic waves
Electromagnetic radiation
Field theory
Nonlinear systems
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Summary:We extend the discussion on the difference between angular momentum and pseudo-angular momentum in field theory. We show that the often quoted expressions in [Phys.Rev.B 103, L100409 (2021)] only apply to a non-linear system, and derive the correct rotation symmetry and the corresponding angular momentum for a linear elastic system governed by Navier-Cauchy equation. By mapping the concepts and methods for the elastic wave into electromagnetic theory, we argue that the renowned canonical and Benlinfante angular momentum of light are actually pseudo-angular momentum. Then, we derive the ``Newtonian" momentum \(\int \text{d}^3 x\boldsymbol{E}\) and angular momentum \(\int \text{d}^3 x (\boldsymbol{r}\times\boldsymbol{E})\) for a free electromagnetic wave, which are conserved quantities during propagation in vacuum.
ISSN:2331-8422