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 group of rigid motions is considered to guide the search for a naturalsystem of space-time coordinates in General Relativity. This search leads us toa natural extension of the space-times that support Painlev\'{e}--Gullstrandsynchronization. As an interesting example, here we describe a system of rigidcoordinates for the cross mode of gravitational linear plane waves.

Rigid covariance as a natural extension of Painlev\'e--Gullstrand space-times: gravitational waves