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Superposition induced topology changes in quantum gravity
We show that superpositions of classical states in quantum gravity with fixed
topology can lead to new classical states with a different topology. We study
this phenomenon in a particular limit of the LLM geometries. In this limit, the
UV complete minisuperspace of allowed quantum states is exactly given by the
Hilbert space of a free chiral boson in two dimensions. We construct this
chiral boson purely in terms of combinatorial objects associated with the
permutation group. As a byproduct of this analysis, we re-derive the
Murnaghan-Nakayama rule for characters of the permutation group. We are able to
express this rule in terms of operator relations for raising and lowering
operators on the Hilbert space of states in a free fermion basis. Our
construction provides a preferred notion of bulk locality by studying an
appropriate notion of D-brane state generating functions. We describe how
multi-droplet LLM geometries with different topologies give new classical
limits of the free chiral boson, even though they can be written as
superpositions of coherent states with trivial topology. As a consequence,
topology cannot be accessed by a single operator measurement in this quantum
system. We study other non-linear measurements in the quantum wave-function,
based on uncertainty and entanglement between modes of the chiral boson, that
can be used as order parameters to measure the topology of such states.Comment: 87 pages (incl. appendices). v2: updated reference
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