Cosmological collider physics and primordial standard clocks

In this talk we will introduce two research programs that aim to understand the physics of the primordial universe, leading up to the Big Bang universe. We will do so by studying the properties of primordial density perturbations that seeded the structure of the universe. In the cosmological collider physics program, we explain how the inflation epoch can function as a high-energy collider, revealing the mass and spin spectrum of massive fields that the Hubble energy excited during inflation. In the primordial standard clocks program, we demonstrate how a signature of massive fields directly encodes the function a(t), representing the primordial universe's scale factor evolution over time. Such a measurement would provide direct evidence for either the inflation scenario or an alternative scenario.