Induced Gravitational Waves as Cosmic Tracers of Leptogenesis

We demonstrate that induced gravitational waves (IGWs) can naturally emerge within the framework of thermal leptogenesis models, thereby providing a robust probe for exploring this theory at remarkably high energy scales. To illustrate this principle, we put forth a basic leptogenesis model in which an early matter-dominated phase, tracing the leptogenesis scale, enhances the generation of gravitational waves induced by an early structure formation. Leveraging recent N-body and lattice simulation results for IGW computations in the non-linear regime, we show that it is possible to establish a direct link between the frequency and amplitude of these IGWs and the thermal leptogenesis scale.