Cosmic string gravitational wave backgrounds at LISA: I. Signal survey, template reconstruction, and model comparison

Abstract We present a catalog of gravitational wave background (GWB) signal templates from cosmic-string networks, based on relevant models proposed in the literature. We classify templates as conventional , based on standard cosmology and Nambu-Goto results (VOS and BOS), and beyond conventional , based on modifications of a) the loop number density (LRS, super, metastable, current-carrying strings), b) the expansion history (non-standard cosmologies, extra degrees of freedom, either thermal or secluded), or c) the loop properties (birth length, power emission). Using the SBI package GWBackFinder : https://github.com/AndronikiDimitriou/GWBackFinder , we quantify the reconstruction precision of each signal by LISA, scanning over their parameter space, and performing model comparisons. For conventional signals, LISA reconstructs the tension Gμ with an error ≲ 10% for Gμ ≳ 5·10 -15 , which decreases down to 2-3% for Gμ ≳ 10 -12 . BOS and VOS modelings become distinguishable confidently for Gμ ≳ 5·10 -13 . For beyond-conventional signals, we identify SNR and error-threshold intervals for each parameter, and determine (for few examples) the regions where they can be distinguished from conventional signals. Analogous quality reconstruction studies of cosmic-string GWBs, superimposed over leading astrophysical foregrounds in the LISA window, will be presented in a series of upcoming papers.