Speaker
Description
Motivated by discrete approaches to quantum gravity, we formulate the covariant Brownian motion of free particles described by a stochastic geodesic equation. At the level of the Fokker-Planck equation, this approach provides the unique covariant diffusion equation in the absence of a preferred frame. The uniqueness makes the equation the effective description of a wide range of possible quantum gravity effects. When applied to dark matter particles, it results in dynamical warming at late times, suppressing the matter power spectrum at small scales. Thus, we show that the model has potential for alleviating the S_8 tension.
When applied to gravitons, the model predicts spreading and drifting of the gravitational-wave power spectrum. Thus, LISA will be able to place bounds on the massless diffusion constants, assuming it detects a peaked spectrum of primordial gravitational waves.
| Keyword-1 | Quantum gravity |
|---|---|
| Keyword-2 | Cosmology |