Archive - Jan 7, 2005 - Blog entry


Cosmological Parameters from Eigenmode Analysis of Sloan Digital Sky Survey Galaxy Redshifts


We present estimates of cosmological parameters from the application of the Karhunen-Loève transform to the analysis of the 3D power spectrum of density fluctuations using Sloan Digital Sky Survey galaxy redshifts. We use mh and fb = b/m to describe the shape of the power spectrum, 8gL" align="middle"> for the (linearly extrapolated) normalization, and to parametrize linear theory redshift space distortions. On scales k 0.16hMpc–1, our maximum likelihood values are mh = 0.264 ± 0.043, fb = 0.286 ± 0.065, 8gL" align="middle"> = 0.966 ± 0.048, and = 0.45 ± 0.12. When we take a prior on b from WMAP, we find mh = 0.207 ± 0.030, which is in excellent agreement with WMAP and 2dF. This indicates that we have reasonably measured the gross shape of the power spectrum but we have difficulty breaking the degeneracy between mh and fb because the baryon oscillations are not resolved in the current spectroscopic survey window function. ©2004 American Institute of Physics


Brane Inflation: From Superstring to Cosmic Strings

S.-H. Henry Tye
Laboratory for Elementary Particle Physics, Cornell University, Ithaca, NY 14853

Brane inflation, where branes move towards each other in the brane world, has been shown to be quite natural in superstring theory. Inflation ends when branes collide and heat the universe, initiating the hot big bang. Cosmic strings (but not domain walls or monopoles) are copiously produced during the brane collision. Using the COBE data on the temperature anisotropy in the cosmic microwave background, the cosmic string tension µ is estimated to be around 10 –6 > Gµ > 10–11, while the present observational bound is 7 × 10 –7 > Gµ. This implies that the anisotropy that seeds structure formation comes mostly from inflation, but with a small component (< 10%) from cosmic string effects. This cosmic string effect should be testable in the near future via gravitational lensing, the cosmic microwave background radiation, and/or gravitational wave detectors like LIGO II/VIRGO. ©2004 American Institute of Physics

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