Frame dragging and Eulerian frames in General Relativity

Understand

The physical interpretation of cold dark matter perturbations is clarified by associating Bertschinger's Poisson gauge with a Eulerian/observer's frame of reference.

• We obtain such an association by using a Lagrangian approach to relativistic cosmological structure formation.
• Explicitly, we begin with the second-order solution of the Einstein equations in a synchronous/comoving coordinate system---which defines the Lagrangian frame, and transform it to a Poissonian coordinate system.
• The generating vector of this coordinate/gauge transformation is found to be the relativistic displacement field.