Attempt to determine the largest scale of primordial density perturbations in the universe
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States)
- Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)
- Laboratory for Astronomy and Solar Physics, Code 685, NASA/GSFC, Greenbelt, Maryland 20771 (United States)
The principle of causality requires that a pure power-law spectrum of cosmological density perturbations possess a super-Hubble suppression scale. We search for evidence of such suppression by performing a three parameter likelihood analysis of the COBE-DMR 4-year sky maps with respect to the amplitude, the spectral index, and the suppression scale. It is found that all suppression scales larger than c/H{sub 0} are consistent with the data, but that scales of order c/H{sub 0} are slightly preferred, at roughly the one-sigma level. Super-Hubble density fluctuations on very large scales ({gt}c/H{sub 0}) can only be explained in the context of present theory by a de Sitter expansion phase, whereas those that are {open_quotes}small{close_quotes} ({approximately}c/H{sub 0}) can also be explained within the standard hot big-bang model. Density perturbations originating after any conceivable de Sitter expansion phase or during non-isentropic de Sitter expansion have natural kinematic constraints which could explain a small super-Hubble suppression scale. Standard inflationary cosmology, which is characterized by isentropic de Sitter expansion, generically predicts that the particle horizon should be much larger than the present-day Hubble radius, c/H{sub 0}. For such scenarios, a small super-Hubble suppression scale would require the duration of the inflation epoch to be fairly short. Suppression scales smaller than c/H{sub 0} are strongly excluded by the COBE data. {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 568379
- Journal Information:
- Physical Review, D, Vol. 57, Issue 4; Other Information: PBD: Feb 1998
- Country of Publication:
- United States
- Language:
- English
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