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Vacuum fluctuations may generate a large cosmological constant. However, without assuming homogeneity or an arrow of time at the Planck scale, this constant averages to zero macroscopically, creating a "spacetime foam" effect visible only at small scales.

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Area of Science:

  • Cosmology
  • Quantum Gravity
  • General Relativity

Background:

  • Standard effective field theory suggests vacuum fluctuations create a large cosmological constant.
  • The cosmological constant's large value presents a significant challenge in modern physics.

Purpose of the Study:

  • To investigate the cosmological constant's behavior without assuming Planck-scale homogeneity or an arrow of time.
  • To explore the implications of general relativistic initial data on small and large scales.

Main Methods:

  • Analysis of general relativistic initial data under relaxed homogeneity and time-arrow assumptions.
  • Examination of spacetime evolution, curvature, expansion, and shear at Planck and macroscopic scales.

Main Results:

  • A large class of initial data exhibit enormous expansions, shears, and curvatures at small scales.
  • These extreme values rapidly average to zero macroscopically.
  • Quantum fluctuations may preserve these Planck-scale properties.

Conclusions:

  • The cosmological constant may be large at the Planck scale but effectively zero at observable scales.
  • This resolves the cosmological constant problem by reconciling theoretical predictions with observations.
  • The findings support a
  • spacetime foam
  • model consistent with Wheeler's ideas.