Observable quantities in cosmological models with strings

The Friedman equation for the universe with arbitrary curvature filled with mutually noninteracting pressureless dust, radiation, cosmological constant, and strings is considered. The explicit solution of the Friedman equation is obtained for specific models. Formulas are derived for luminosity distance, angular diameter, and source counts, which may serve for testing the string-dominated universe. It seems that the most sensitive test, at least from the formal point of view, is the formula for the number of galaxies N(z) corresponding to a given value of the redshift. It is shown that the maximum of N(z) strongly depends on the density of strings, especially if the density is large enough to explain the Omega problem. (Author)