English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Open

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

One intriguing issue in the nucleon spin decomposition problem is theexistence of two types of decompositions, which are representably characterizedby two different orbital angular momenta (OAMs) of quarks. The one is themanifestly gauge-invariant mechanical OAM, while the other is the so-calledgauge-invariant canonical (g.i.c.) OAM, the concept of which was introduced byChen et al. To get a deep insight into the difference of these twodecompositions, it is therefore vitally important to understand the thephysical meanings of the above two OAMs correctly. Also to be clarified is theimplication of the gauge symmetry that is immanent in the concept of g.i.c.OAM. We find that the famous Landau problem provides us with an ideal tool toanswer these questions owing to its analytically solvable nature. Afterderiving a complete relation between the standard eigen-functions of the LandauHamiltonian in the Landau gauge and in the symmetric gauge, we try to unravelthe physics of the the canonical OAM and the mechanical OAM, by paying specialattention to their gauge-dependence. We also argue that, different from themechanical OAM of the electron, the canonical OAM or its gauge-invariantversion would not correspond to any direct observables at least in the Landauproblem. Also briefly discussed is the uniqueness or non-uniqueness problem ofthe nucleon spin decomposition, which arises from the arbitrariness in thedefinition of the so-called physical component of the gauge field.

The issue of gauge choice in the Landau problem and the physics of canonical and mechanical orbital angular momenta