## [astro-ph/0211653] Bias and the power spectrum beyond the turn-over [Wot no turnover?!]

 Authors: Ruth Durrer, Andrea Gabrielli, Michael Joyce, Francesco Sylos Labini Abstract: Threshold biasing of a Gaussian random field gives a linear amplification of the reduced two point correlation function at large distances. We show that for standard cosmological models this does not translate into a linear amplification of the power spectrum (PS) at small k. For standard CDM type models this means that theturn-over'' at small k of the original PS disappears in the PS of the biased field for the physically relevant range of the threshold parameter. In real space this difference is manifest in the asymptotic behaviour of the normalised mass variance in spheres of radius R, which changes from the super-homogeneous'' behaviour to a Poisson-like behaviour.This qualitative change results from the intrinsic stochasticity of the threshold sampling. While our quantitative results are specific to the simplest threshold biasing model, we argue that our qualitative conclusions should be valid generically for any biasing mechanism involving a scale-dependent amplification of the correlation function. One implication is that the real-space correlation function will be a better instrument to probe for the underlying Harrison Zeldovich spectrum in the distribution of visible matter, as the characteristic asymptotic negative power-law \xi (r) \sim -r^{-4} tail is undistorted by biasing. [PDF]  [PS]  [BibTex]  [Bookmark]

Discussion related to specific recent arXiv papers
Sarah Bridle
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### [astro-ph/0211653] Bias and the power spectrum beyond the tu

This paper claims that threshold biasing will boost the galaxy power spectrum on both small and large scales, and that this may even remove the turnover in the galaxy power spectrum completely (with the galaxy power spectrum just flattening off to a constant level on scales larger than the matter power spectrum turnover).

This is a v surprising result! I had always assumed that seeing the turnover in the galaxy power spectrum was a major goal in itself, as well as being a potential probe of dark energy (eg. Cooray). People don't seem to mention this paper - why is this? Is it wrong?/overlooking something? (Or have I been speaking to the wrong people!?) Or should we be worrying more about this effect?!