Speaker
Description
Positive, although very small, value of the cosmological constant changes behaviour of a central gravitational field at large distances. Crucial for our discussion is existence of a static radius where gravitational attraction of a centre is just balanced by cosmic repulsion. Analysis of radial timelike geodesics in the Schwarzschild-de Sitter spacetime reveals that particles with specific energy close to unity have tendency to slow down and cluster near the static radius, forming clumps which, subsequently, start to expand due to cosmic repulsion. For central masses of $(10^6$-$10^{11})\,{\rm M_{\odot}}$ and current value of the cosmological constant $1.1\times 10^{-52}$ ${\rm m^{-2}}$, this phenomenon takes place at distances of tens to hundreds of kiloparsecs from the centre, which are distances in which large-scale jets and huge radio-lobes were observed in some active galaxies.