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Abstract |
The generation of white noise on large scales is a generic property of the dynamics of physical systems described by local nonlinear partial differential equations. Nonlinearities prevent the small-scale dynamics from being erased by smoothing. Unresolved small-scale dynamics act as an uncorrelated (white or Poissonian) noise (seemingly stochastic but actually deterministic) contribution to large-scale dynamics. This white noise exists even when the dynamics is very nearly linear. In cases where the power spectrum is sub-Poissonian on large scales, this noise will dominate on the largest scale power no matter the amplitude of the inhomogeneities. Such is the case in the standard model of cosmology, where the primordial density power spectrum is expected to have an almost Harrison-Zel'dovich, P[k] k, spectrum on a much broader range of scales than can be observed. Even though linear gravitational evolution dominates nonlinear corrections by a factor of 105, the nonobservation of white noise on the Hubble scale precludes the extrapolation of this power law below the comoving 1 pc scale. More generally, observation or nonobservation of large-scale white noise provides a powerful probe of the Universe on very small scales in the early Universe. Gravitational radiation, phase transitions, vorticity, and running of the spectral index are all phenomena that can be probed with large-scale white noise. Large-scale white noise is a nonoptional feature of all cosmological models but one which has not heretofore been appreciated. |
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Address |
[Barenboim, Gabriela] Univ Valencia, CSIC, Inst Fis Corpuscular, Paterna 46980, Spain; [Barenboim, Gabriela] Univ Valencia, Dept Fis Teor, Burjassot 46100, Spain; [Ireland, Aurora] Univ Chicago, Dept Phys, Chicago, IL 60637 USA; [Ireland, Aurora] Stanford Univ, Leinweber Inst Theoret Phys, Stanford, CA 94305 USA; [Stebbins, Albert] Fermilab Natl Accelerator Lab, Theoret Astrophys Grp, Batavia, IL 60510 USA, Email: gabriela.barenboim@uv.es; |
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