Speaker
Description
This talk focuses on gravitational-wave backgrounds (GWB) from cosmic strings that would manifest only at ultra-high frequencies (above kilohertz), that leave no signal at either LIGO, Einstein Telescope, or LISA, and correspond to high-energy scale (beyond $10^{10}$ GeV) particle physics parameters. Signals from metastable local strings, with amplitude as large as the $\Delta N_{\rm eff}$ bounds, offer exciting prospects to probe grand unification physics. Beyond the information of the symmetry-breaking scale, the high-frequency spectrum encodes the microscopic structure of the strings through the position of the UV cutoff. The detection of such cut-off enables the reconstruction of the scalar potential, particularly the scalar self-coupling. We estimate the needed reach of hypothetical futuristic GW detectors to probe such GW and, therefore, the corresponding high-energy physics processes. On the other hand, the GWB from global axionic strings is suppressed even for large symmetry-breaking scales due to the matter era from the associated heavy axions. (Based on 2312.09281)
