Inverse Gertsenshtein effect as a probe of high-frequency gravitational waves
Yutong He (Nordita, Stockholm)
Tuesday 19/03/2024 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
High-frequency (>> kHz) gravitational waves (HFGWs) directly indicate new physics, such as beyond-Standard-Model mechanisms or sub-stellar mass primordial black holes. We apply the inverse Gertsenshtein effect, i.e., conversion of GWs to photons of the same frequency in external magnetic fields, to constrain HFGW energy densities from MHz to THz. The constraints are derived by analysing the GW-induced photons in cosmic magnetic fields as a distortion of the blackbody Cosmic Microwave Background (CMB). No existing instruments/measurements yield HFGW constraints competitive to the cosmic overclosure limit or the Big Bang Nucleosynthesis (BBN) bound. However, this can be significantly improved with the upcoming Square Kilometre Array and proposed next-generation CMB surveys, the latter of which could potentially reach the BBN bound in the THz regime. We present a preliminary forecast study on the constrainig power expected of these future sky surveys.