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Area of Science:

  • Quantum gravity
  • Cosmology
  • Theoretical physics

Background:

  • De Sitter spacetime is a key model in cosmology.
  • Understanding quantum gravity is crucial for describing early universe and black holes.
  • Jackiw-Teitelboim gravity offers a simplified framework for quantum gravity studies.

Purpose of the Study:

  • Investigate time evolution in Jackiw-Teitelboim gravity with a positive cosmological constant.
  • Determine if time evolution is unitary or isometric.
  • Analyze the implications for the de Sitter S matrix.

Main Methods:

  • Studied a simplified model of de Sitter quantum gravity (Jackiw-Teitelboim gravity).
  • Analyzed the mathematical properties of time evolution in this model.
  • Identified states projected out during time evolution.

Main Results:

  • Time evolution was found to be isometric, not unitary.
  • States corresponding to crunching initial conditions are projected out.
  • Bulk physics knowledge, even over long timescales, is insufficient to determine the de Sitter S matrix.

Conclusions:

  • The isometric nature of time evolution has significant implications for quantum gravity.
  • The projection of crunching states suggests a loss of information or a specific boundary condition.
  • The de Sitter S matrix cannot be fully deduced from bulk physics alone in this model.