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/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The definition of the Hamiltonian operator H for a general wave equa-tion ina general spacetime is discussed. We recall that H depends on the coordinatesystem merely through the corresponding reference frame. When the wave equationinvolves a gauge choice and the gauge change is time-dependent, H as anoperator depends on the gauge choice. This dependence extends to the energyoperator E, which is the Hermitian part of H. We distinguish between thisambiguity issue of E and the one that occurs due to a mere change of the"represen-tation" (e.g. transforming the Dirac wave function from the "Diracrepresentation" to a "Foldy-Wouthuysen representation"). We also assert thatthe energy operator ought to be well defined in a given ref-erence frame at agiven time, e.g. by comparing the situation for this operator with the mainfeatures of the energy for a classical Hamilto-nian particle.

On the Hamiltonian and energy operators in a curved spacetime, especially for a Dirac particle