Physics – High Energy Physics – High Energy Physics - Theory
Scientific paper
2002-03-13
Phys.Rev. D66 (2002) 023517; AAPPS Bull. 12N1 (2002) 10-20
Physics
High Energy Physics
High Energy Physics - Theory
10 pages
Scientific paper
10.1103/PhysRevD.66.023517
We propose a variation of spacetime noncommutative field theory to realize the stringy spacetime uncertainty relation without breaking any of the global symmetries of the homogeneous isotropic universe. We study the spectrum of metric perturbations in this model for a wide class of accelerating background cosmologies. Spacetime noncommutativity leads to a coupling between the fluctuation modes and the background cosmology which is nonlocal in time. For each mode, there is a critical time at which the spacetime uncertainty relation is saturated. This is the time when the mode is generated. These effects lead to a spectrum of fluctuations whose spectral index is different from what is obtained for commutative spacetime in the infrared region, but is unchanged in the ultraviolet region. In the special case of an exponentially expanding background, we find a scale-invariant spectrum. but with a different magnitude than in the context of commutative spacetime if the Hubble constant is above the string scale.
Brandenberger Robert
Ho Pei-Ming
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