HECAP Seminar: Primordial-Tensor-Induced Stochastic GWs: Explaining the Recent PTA Signal With No PBH Production
Starts 15 Feb 2024 16:00
Ends 15 Feb 2024 17:30
Central European Time
L. Stasi Seminar Room and via Zoom
Recently, pulsar timing array (PTA) collaborations announced evidence for an isotropic stochastic gravitational wave (GW) background. The origin of the PTA signal can be astrophysical or cosmological. In the latter case, the so-called secondary scalar-induced GW scenario is one of the viable explanations, but it has a potentially serious issue of the overproduction of primordial black holes (PBHs) due to the enhanced curvature perturbation. We present a new interpretation of the PTA signal. Namely, it originated from an extra spectator tensor field that exists on top of the metric tensor perturbation. As the energy density of the extra tensor field is always subdominant, it cannot lead to the formation of PBHs. Thus our primordial-tensor-induced scenario is free from the PBH overproduction issue. Based on arXiv:2302.14080 and arXiv:2307.13109.