arXiv subjects

J. H. P. Wu

Publications and source records attributed to J. H. P. Wu.

22 records · Page 2Linked to original sources

arXiv1999

The cluster abundance in cosmic string models for structure formation

We use the present observed number density of large X-ray clusters to constrain the amplitude of matter density perturbations induced by cosmic strings on the scale of $8 h^{-1}$Mpc ($σ_8$), in both open cosmologies and flat models with a non-zero cosmological constant. We find a slightly lower value of $σ_8$ than that obtained in the context of primordial Gaussian fluctuations generated during inflation. This lower normalization of $σ_8$ results from the mild non-Gaussianity on cluster scales, where the one point probability distribution function is well approximated by a $χ^2$ distribution. We use our estimate of $σ_8$ to constrain the string linear energy density $μ$ and show that it is consistent with the COBE normalization.

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arXiv1998

Cosmic string loops and large-scale structure

We investigate the contribution made by small loops from a cosmic string network as seeds for large-scale structure formation. We show that cosmic string loops are highly correlated with the long-string network on large scales and therefore contribute significantly to the power spectrum of density perturbations if the average loop lifetime is comparable to or above one Hubble time. This effect further improves the large-scale bias problem previously identified in earlier studies of cosmic string models.

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arXiv1998

Non-gaussian Features of Linear Cosmic String Models

We investigate the non-gaussian properties of cosmic-string-seeded linear density perturbations with cold and hot dark matter backgrounds, using high-resolution numerical simulations. We compute the one-point probability density function of the resulting density field, its skewness, kurtosis, and genus curves for different smoothing scales. A semi-analytic model is then invoked to provide a physical interpretation of our results. We conclude that on scales smaller than $1.5{(Ωh^2)}^{-1}$Mpc, perturbations seeded by cosmic strings are very non-gaussian. These scales may still be in a linear or mildly non-linear regime in an open or $Λ$-universe with $Γ=Ωh \lsim 0.2$.

astro-ph↗

arXiv1998

Cosmic-String-Seeded Structure Formation

We describe the results of high-resolution numerical simulations of string-induced structure formation in open universes and those with a non-zero cosmological constant. For models with $Γ= Ωh = 0.1 - 0.2$ and a cold dark matter background, we show that the linear density fluctuation power spectrum has both an amplitude at $8 h^{-1} Mpc, σ_8$, and an overall shape which are consistent within uncertainties with those currently inferred from galaxy surveys. The cosmic string scenario with hot dark matter requires a strongly scale-dependent bias in order to agree with observations.

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