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SUMMARY:No-boundary observations [Confirmed]
DTSTART:20250306T193000Z
DTEND:20250306T210000Z
DTSTAMP:20260419T172600Z
UID:indico-event-1059@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Andreas Blommaert (IAS)\n\nI discuss work in progres
 s on the no-boundary state of the universe in quantum cosmology\, emphasiz
 ing the key role played by the inclusion of an observer in obtaining a rea
 sonable no-boundary state. For concreteness we focus on a 2d toy model\, n
 amely dS JT gravity. This model has avatars of important issues with the w
 avefunction of the universe in inflationary models. The issues are that th
 e wavefunction predicts a small universe (whereas our universe is rather l
 arge)\, and that it is not normalizable. I show that the non-normalizabili
 ty is resolved by promoting dS JT gravity to sine dilaton gravity\, a type
  of UV completion of dS JT gravity of which I discuss the cosmological int
 erpretation. I then argue that the issue of predicting a small universe (i
 n this toy model) is resolved by including an observer in the theory. With
  the observer\, the leading contribution is a bra-ket wormhole. The observ
 er's no boundary state is a (maximally mixed) identity matrix\, and thus p
 refers neither small nor large universes.\n\nhttps://events.perimeterinsti
 tute.ca/event/1059/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/1059/
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