Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops.

The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f , the fraction of cosmic string loops which collapse to form black holes, and µ, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and µ is due to the energy density in 100M eV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict µ, and therefore limit the viability of the cosmic string large-scale structure scenario. 0 I. Introduction The cosmic string scenario for the formation of large scale structure has many observable features. Primarily, cosmic strings may serve to produce perturbations to the cosmological fluid of the necessary magnitude and distribution to seed the formation of galaxies and clusters, as observed today. Cosmic strings leave an observational signature through these perturbations, as well as through the emission of gravitational radiation. Broadly, then, there are two areas of cosmic string research. These are studies of the large-scale structure produced by cosmic strings, and tests of the compatibility of cosmic strings with cosmological observations. Such tests focus, for example, on the anisotropies produced by cosmic strings in the microwave background and the noise in pulsar timing due to the cosmic string stochastic gravitational wave background. Ultimately, the test of compatibility results in a restriction on µ, the mass-per-unit-length and sole free parameter in the cosmic string model. In this report, we will examine the restrictions on black holes formed from collapsed cosmic string loops. It is well known that a sufficiently smooth, circular cosmic string loop may collapse to form a black hole [1,2,3,4,5]. During the evolution of a network of cosmic strings, some cosmic string loops may collapse to form black holes. In this case, the observational restrictions on a population of primordial black holes may be used to restrict such a cosmic string scenario. The study of primordial black holes has been vigorously carried out in, for example, [6,7,8,9,10,11,12]. We will take advantage of this work in applying constraints to a population of black holes formed from collapsed cosmic string loops. In turn, we will place restrictions on the cosmic string network. In this paper, …