Cosmic Strings and Structure Formation

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We discuss structure formation in cosmic string theories. Emphasis is laid on the properties of the peculiar velocity field, non-gaussian features and clusters of galaxies. It is found that the predicted peculiar velocity field is quiet (v<150 km/s for L>30 h⁻¹ Mpc) for models with (Ω₀ h ≤ 0.2) which is in disagreement with the results from POTENT at large scales (>30h⁻¹ Mpc), consistent, however, with the analysis of the peculiar velocity field of spiral galaxies by Giovannelli et al.. Using the Press-Schechter formalism we calculate the abundances of X-ray clusters. It is found that in CDM models a mass fluctuation σ₈ = 0.6...0.7 is needed with Ω₀ h =0.1...0.2 in order to explain the current data.