Origin of the initial population of small string loops

Develop a detailed analysis of realistic scenarios that can produce the initial population of isolated, small cosmic string loops assumed as starting conditions for the percolation mechanism of fundamental strings during a kination epoch, considering sources such as quantum nucleation in time-dependent backgrounds, evaporation of ultra-small primordial black holes, and products from brane/antibrane annihilation at the end of inflation.

Background

The paper proposes a new mechanism for forming cosmic (super)string networks in which initially isolated small loops grow and percolate due to a time-decreasing tension in a kination background. The authors assume an initial population of small loops but do not provide a detailed derivation of their origin.

They mention several plausible production channels—quantum nucleation in a time-dependent background, evaporation of ultra-small primordial black holes, and products from brane/antibrane annihilation following inflation—but explicitly defer a comprehensive analysis of these scenarios.