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

For the S-states of muonium and positronium, the hyperfine shifts to theorder $\alpha^6$ of a recently derived two-fermion equation with explicit $\calCPT$-invariance are checked against the results of a nonrelativistic reduction,and the leading $\alpha^8$ shifts are calculated. An additional hyperfineoperator is discovered which can milden the singularity for $r\to 0$ of theDirac hyperfine operator, such that the resulting extended operator can be usednonperturbatively. The binding correction to magnetic moments is mentioned

calCcalPcalT-invariant two-fermion Dirac equation with extended hyperfine operator