Abstract
General properties of gravitational waves in Einstein gravity theory extended to any higher number of dimensions D are investigated. Using the equation of geodesic deviation, evaluated with respect to an observer's natural orthonormal frame, exact spacetimes representing gravitational waves can be identified by specific purely transverse effects on free test particles.
There are D(D-3)/2 independent polarization states due to the corresponding transverse components of the gravitational field typical for spacetimes of algebraic type N. As an explicit example, we study a complete family of exact ppwaves and discuss the resulting measurable effects on particles.
With higher dimensions there occur some completely new effects. For example, the tidal deformations caused by higher-dimensional gravitational waves need not be tracefree, when they are observed by a detector located in four-dimensional physical subspace.