# Black holes are excellent scramblers, but can they scramble points in the string-theory landscape?

Consider the usual derivation of Hawking radiation, using quantum field theory (QFT) in the spacetime of a collapsing star. At late times, long after the event horizon has formed, Hawking radiation is independent of the details of the collapse that formed the event horizon. This independence famously leads to the information loss paradox. However, it still depends on which QFT we use. For example, if we use a QFT that doesn't have any spin-$$1$$ particles in flat spacetime, then the Hawking radiation won't contain any spin-$$1$$ particles, either.

According to the landscape concept, string theory has lots of different "vacua" — lots of different possible low-energy effective theories. Since the particle content of Hawking radiation can be derived using the low-energy effective QFT, it must also depend on which point we choose in the string-theory landscape when Hawking radiation is derived using string theory.

Is this right? I'm no string theory expert, but I had the impression that black holes in string theory were excellent scramblers, taking whatever goes in and scrambling it beyond practical recognition (even if the information is still recoverable in principle). But the preceding argument seems to say that the scrambling abilities of a black hole are limited: they can't scramble different points in the landscape with each other. Is this right?

Or can black holes mix different points in the landscape, too? If so, then where are the flaw(s) in my reasoning?

• I'm unsure what "scrambling points in the string theory landscape" is supposed to mean here - the points in the landscape are choices for the structure of spacetime as our 4d world times a CY manifold + choices of certain flux cycles, i.e. they are a "global" state of the universe. A black hole is a local phenomenon in (and itself part of !) this spacetime - how is it supposed to "scramble" the overall geometrical structure of spacetime? Dec 23, 2020 at 23:03
• @ACuriousMind That's a good point, and that's exactly the kind of thing I wasn't sure about. I don't have a clear picture of the landscape idea, in particular of how "global" the state is that corresponds to a point in the landscape. Since spacetime is emergent in string theory anyway, except maybe for prescribed asymptotic conditions, and since black holes mess with the smooth-spacetime-manifold model (holographic principle), I was vaguely thinking that maybe black holes can also mess with where we are in the landscape. Not a well-formed thought. Dec 24, 2020 at 2:10
• “Scrambling points of landscape” is the property not of black hole but of de Sitter horizons within the context of eternal inflation: an observer cannot know what vacuum lies outside his horizon. Dec 24, 2020 at 6:00

Your third paragraph is correct. Both the entropy, and the Hawking radiation (if supersymmetry is broken) of a stringy Calabi-Yau black hole depend on the details of the effective low energy theory. It is also plausible that the full black hole partition of a black hole, actually depends on all moduli (vector and hyper multiplets) of the background in which a particular black hole solution is found. See section 7.4 in Black Hole Attractors and the Topological String and Holomorphic anomalies in topological field theories for details in the case of a $$\mathcal{N}=2$$ solution in four dimensions.