Similar constructions work for the Reissner–Nordström geometry [398
], as long as one does not get too close to the
singularity. (With
one needs
to avoid an imaginary fluid velocity.) Likewise, certain aspects of the Kerr
geometry can be emulated in this way [641
]. (One needs
in the Doran coordinates [176, 633
] to avoid closed timelike
curves.) As a final remark, let us note that de Sitter space corresponds to
and
. For further details see
Section 2.5.