Time Travel Back From The Future in The Darkl Matter Galactic Halo?

Hawking and Ellis show that anti-DeSitter space-time has closed timelike
curves!
Dark energy corresponds to DeSitter space-time that is well behaved on
cosmological scale with no closed timelike curves. However on a smaller
scale like the galactic dark matter halos, if the dark matter densities
are approximately uniform the dominating metric field they create may be
approximately anti-DeSitter. This would fit Colonel Corso's remarks from
his private notes that the alleged Roswell aliens were time travelers
from our future. In that case they would have to be from our galaxy,
i.e. within a spherical dark matter halo of approximately uniform
negative zero point energy density and positive pressure. It's
interesting that Hawking and Ellis had no inkling of the dark energy and
dark matter as zero point vacuum energy of positive and negative energy
density respectively when they wrote their book in 1973. The edition I
have is 1995 and no mention of dark matter there in connection with
anti-DeSitter spacetime. No inkling of dark energy as well a scant ten
years ago.