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SUMMARY:Julian De Vuyst (Okinawa Institute of Science and Technology)
DTSTART:20240709T070000Z
DTEND:20240709T080000Z
DTSTAMP:20260417T072625Z
UID:3cqfs/22
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/3cqfs/22/">G
 ravitational entropy is observer-dependent</a>\nby Julian De Vuyst (Okinaw
 a Institute of Science and Technology) as part of Tricontinental Quantum F
 undamentals Seminar\n\n\nAbstract\nIn quantum gravity\, it has been argued
  that a proper accounting of the role played by an observer promotes the v
 on Neumann algebra of observables in a given spacetime subregion from Type
  III to Type II. While this allows for a mathematically precise definition
  of its entropy\, we show that this procedure depends on which observer is
  employed. We make this precise by considering a setup in which many possi
 ble observers are present\; by generalising previous approaches\, we deriv
 e density operators for the subregion relative to different observers (and
  relative to arbitrary collections of observers)\, and we compute the asso
 ciated entropies in a semiclassical regime\, as well as in some specific e
 xamples that go beyond this regime. We find that the entropies seen by dis
 tinct observers can drastically differ. Our work makes extensive use of th
 e formalism of quantum reference frames (QRF)\; indeed\, as we point out\,
  the 'observers' considered here and in the previous works are nothing but
  QRFs. In the process\, we demonstrate that the description of physical st
 ates and observables invoked by Chandrasekaran et al. <a href="https://arx
 iv.org/abs/2206.10780">[arXiv:2206.10780]</a> is equivalent to the Page-Wo
 otters formalism\, leading to the informal slogan "PW=CLPW". It is our hop
 e that this paper will help motivate a long overdue union between the QRF 
 and quantum gravity communities.\n
LOCATION:https://researchseminars.org/talk/3cqfs/22/
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