2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/5762We have analyzed the dependences of the threshold value of amplitude of linear density fluctuation collapsed at the current epoch, $δ_c$, and its overdensity after virialization, $Δ_c$, on matter density content, 3D curvature parameter and cosmological constant. Though the range for the threshold values of perturbation amplitude is quite narrow - $1.55\le δ_c\le 1.75$ in the region of parameters $-0.4\leΩ_k\le0.4$, $0\leΩ_Λ\le 1$, $0.1\leΩ_m\le 1$, the difference in the concentrations of rich clusters of galaxies (calculated within the Press-Schechter formalism framework) with real and with canonical values of $δ_c$ reaches, and for some models exceeds, 30%. The range of changes for the overdensity after virialization, $Δ_c$, is considerably wider for the same region of parameters: $60\leΔ_c\le180$. It results into difference up to $\sim40$% between the X-ray temperatures of gas, as calculated for these values and for the canonical value of $Δ_c=178$. Also we have found analytical approximations of the dependences $δ_c(Ω_m,Ω_Λ)$ and $Δ_c(Ω_m,Ω_Λ)$ with their accuracies for above mentioned region of parameters being no worse than 0.2% and 1.7% respectively.17 pages, 8 figures, LaTeX (Accepted for publication by Journal of Physical Studies, 2003, No1)Astrophysicstext