This approach was first used, in the context of varying-fine structure theories (Mota & Barrow 2004a,b).

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This assumption will be made throughout the paper.

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... $\Delta_{\rm c}\approx 147$

If we would define $\Delta_{\rm c2} = \rho_{\rm cdm,cluster}(t_{\rm V})/\rho_{\rm cdm,backgr}(t_{\rm c})$ , where $t_{\rm c}$ is the collapse time, its value in the Einstein-de Sitter model would be approximately 178. However, for computational convenience, we consider instead the quantity $\Delta _{\rm c}$ at the time of virialisation. $\Delta _{\rm c}$ and $\Delta_{\rm c2}$ differ only by a factor from each other.

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