Galactic Patrol Back From The Future
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.