Physical geometry of the quasispherical Szekeres models
  The quasispherical Szekeres metric is an exact solution to Einstein's
equations describing an inhomogeneous and anisotropic cosmology. Though its
governing equations are well-known, there are subtle, often-overlooked details
in how the model's functions relate to its physical layout, including the
shapes and relative positions of structures. We present an illustrated overview
of the quasispherical Szekeres models and show exactly how the model functions
relate to the physical shape and distribution of matter. In particular, we
describe a shell rotation effect that has not previously been fully understood.
We show how this effect relates to other known properties, and lay out some
mathematical tools useful for constructing models and picturing them
accurately.
