A cosmological model with a negative Lambda term and strings of infinite length

It is shown that the solution of the Friedmann equation with negative vacuum density and with account for the density of strings going beyond the horizon (infinite strings) is the same for spaces of negative, zero, and positive curvature. The model presented satisfies the value of the deceleration parameter q₀ = 0.5, of the expansion parameter H₀ = 50 km/s Mpc, and yields the age of the Universe from the beginning of the expansion of 16 billion years. The model also predicts a stop in the expansion and the subsequent contraction of the Universe. For a flat space and for the present density of the nonrelativistic matter 5×10^-31g/cm³ the model yields the vacuum density -2×10^-30g/cm³, the string density 6×10^-30g/cm³; the stop will occur 43 billion years after the beginning of the expansion. Other features of the model as well as possible observational tests are discussed.