Properties of Interacting Cosmic String Networks.

摘要

We have studied by means of numerical simulations the dynamical evolution of a network of cosmic strings, in order to extract the main statistical properties of this system. Our basic conclusion is that scaling solutions exist, both in the radiation and matter era. In such a scaling solution the string energy density evolves as t sup -2 , which requires that the process by which long strings dump their energy into closed loops (which can gravitationally radiate away) is efficient enough to prevent the string domination over other forms of energy. On the other hand, the generated spectrum of loop sizes does depend on the value of our numerical lower cutoff (i.e., the minimum length of loop we allow to be chopped off the network). Still, it seems very likely that the network evolution is very different from the ''standard model'' in which a few horizon sized loops are created per horizon volume and per Hubble time (which subsequently fragment into about 10 smaller ''daughter'' loops). Rather, many tiny loops are directly cut from the network of infinite strings, and it appears that the only fundamental scale (the horizon) has been lost. This is probably because a fundamental ingredient had been overlooked, namely the kinks. These kinks are created in pairs at each intercommutation, and very rapidly, the long strings appear to be very ''kinky''. Thus the number of long strings per horizon is still of the order of a few, but their total length is fairly large. As far as the astrophysical consequences of our work are concerned, the most obvious implication stems from the increase in length per horizon volume of the infinite strings, which means that the infall of matter onto long string wakes will be enhanced, and might even dominate. We have also computed the two-point correlation function of the loops and confirm that, as in the work of Turok, loops are at birth correlated in much the same way as the Abell clusters. 22 refs., 10 figs. (ERA citation 14:009918)