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

Notation for spin coefficients for metrics of neutral signature in fourdimensions is introduced. The utility and interpretation of spin coefficientsis explored through themes in null geometry familiar from (complex) generalrelativity. Four-dimensional Walker geometry is exploited to provide examplesand the generalization of the real neutral version of Pleba\~nski's (1975)second heavenly equation to certain Walker geometries given in Law andMatsushita [16] is extended further.

Spin coefficients for four-dimensional neutral metrics, and null geometry