But our universe adheres to AdS constraints. As far as we know.
When you reach the information density limit in AdS, in our universe you get a black hole.
When you reach the information density limit in AdS, in our universe you get a black hole.
No, as far as we know, it doesn't since the cosmological constant is slightly positive, so the universe would best be described by de Sitter spacetime, not anti-de Sitter.
Obviously you can stick GR in AdS, but AFAIK nothing about that would've seemed interesting with regards to holography before Maldacena, let alone plausibly providing inspiration to a fiction author.
To be less roundabout than my previous comment: I think Baxter may have been inspired by the holographic principle in general, but I doubt AdS crossed his mind at all when he was writing these stories in the 80s and early 90s.
(EDIT: or maybe Baxter was thinking about AdS but not about holography. I haven't read his work.)
Stephen Baxter is known for sch-fi so hard it'll cut you. He may have just accidentally come up with similar concepts during the same year.
Think of the spaces in ADS/CFT as mathematical spaces, not physical spaces. It lets you take a model constructed in one space, translate it into another space, perform some calculations there that might be simpler and then translate them back.