Cosmological properties of a class of $\Lambda$ decaying cosmologies

Abstract

We investigate some properties of flat cosmological models with a $\Lambda$ term that decreases with time as $\Lambda \propto a^{-m}$ (a is the scale factor and m is a parameter $0\le m<3$). The models are equivalent to standard cosmology with matter and radiation plus an exotic fluid with the equation of state $p_x=(m/3-1){\rho }_x$. We study the effect of the decaying $\Lambda$ term on the cosmic microwave background (CMB) anisotropy and by using a seminumeric method we compute the angular power spectrum (up to l=20) for different values of m and ${\Omega }_{m0}$. We also investigate the constraints imposed on the models by the magnitude-redshift test in which high-redshift type Ia supernovae (SNe Ia) are used as standard candles. We obtain the 95.4%, 90%, and 68% confidence levels on the parameters m and ${\Omega }_{m0}$ and compare them with those arising from lensing statistics. Our analysis reveals that the SNe Ia constraints are stronger for low values of m and ${\Omega }_{m0}$, while those from lensing statistics are more important for $m>\sim 1$. Models with ${\Omega }_{m0}>\sim 0.2$ and $m>\sim 1.6$ are in good agreement with the data.

RevTex style format,to appear in Phys. Rev. D, 8 pages, 4 eps figures included with epsf, minor changes

References in corpus (1)

• CDM Models with a Smooth Component

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