The number of cosmic string loops

Understand

Using recent simulation results, we provide the mass and speed spectrum of cosmic string loops.

• This is the quantity of primary interest for many phenomenological signatures of cosmic strings, and it can be accurately predicted using recently acquired detailed knowledge of the loop production function.
• We emphasize that gravitational smoothing of long strings does not play any role in determining the total number of existing loops.
• We derive a bound on the string tension imposed by recent constraints on the stochastic gravitational wave background from pulsar timing arrays, finding $G\mu \leq 2.8\times 10^{-9}$.