Degeneracy between CCDM and $\mathrm{\Lambda }\mathrm{CDM}$ cosmologies

The creation of cold dark matter cosmology model is studied beyond the linear perturbation level. The skewness is explicitly computed, and the results are compared to those from the $\mathrm{\Lambda }\mathrm{CDM}$ model. It is explicitly shown that both models have the same signature for the skewness and cannot be distinguished by using this observable.

Figure 1

(a) The ratio of growth function at second order $D_2$, as a function of the scale factor, and (b) the ratio of skewness $S_3$, as a function of the redshift, between the CCDM and $\mathrm{\Lambda }\mathrm{CDM}$ models and for different values of $\beta$. In both cases, the total density $\rho$ is included, Eq. (2.5), for the CCDM. When including only the clustering part (see the text), $w=0$, ${\rho }^{\mathrm{CCDM}}\to {\rho }_m^{\mathrm{\Lambda }\mathrm{CDM}}$, and both CCDM and $\mathrm{\Lambda }\mathrm{CDM}$ become fully degenerate.