Speaker
Description
We compute the gravitational wave (GW) spectrum from scaling global cosmic string networks across infrared and ultraviolet scales. In the infrared (k ≲ ℓ^{-1}), we derive the spectrum analytically using the unequal time correlator (UETC) of the string stress-energy tensor within the unconnected segment and loop model (USLM), a new extension of the unconnected segment model that incorporates the loop contribution for the first time. In the ultraviolet (k ≳ ℓ^{-1}), we develop a data-driven method that connects the UETC formalism to the instantaneous radiation power spectrum measured in lattice simulations. We show that the loop contribution dominates over long strings at all observable frequencies. Confronting the predicted spectra with current and projected observational sensitivities, we derive new constraints on the symmetry-breaking scale fa and the axion mass ma.