Tracing the Dark Matter Sheet in Phase Space

Understand

The primordial velocity dispersion of dark matter is small compared to the velocities attained during structure formation.

• The initial density distribution is close to uniform and it occupies an initial sheet in phase space that is single valued in velocity space.
• Because of gravitational forces this three dimensional manifold evolves in phase space without ever tearing, conserving phase-space volume and preserving the connectivity of nearby points.
• N-body simulations already follow the motion of this sheet in phase space.