Here, we review the most recent progress in our understanding of quantum mechanical
observables in cosmology in the perturbative regime. It relies on an approach that considers …

We discuss peculiarities of quantum fields in de Sitter (dS) space on the example of the self-
interacting massive real scalar, minimally coupled to the gravity background. Nonconformal …

This white paper summarizes recent progress in the cosmological bootstrap, an approach to
the study of the statistics of primordial fluctuations from consistency with unitarity, locality and …

A bstract We study the fundamentals of quantum field theory on a rigid de Sitter space. We
show that the perturbative expansion of late-time correlation functions to all orders can be …

A bstract Calculating the quantum evolution of a de Sitter universe on superhorizon scales is
notoriously difficult. To address this challenge, we introduce the Soft de Sitter Effective …

A bstract Stochastic Inflation is an important framework for understanding the physics of de
Sitter space and the phenomenology of inflation. In the leading approximation, this approach …

We study quantum field theories placed on a two-dimensional de Sitter spacetime (dS 2)
with an eye on the group-theoretic organization of single and multi-particle states. We …

We show that global de Sitter space is unstable to particle creation, even for a massive free
field theory with no self-interactions. The O (4, 1) de Sitter invariant state is a definite phase …

There are at least three different types of secular effects in the two-point correlation functions
in scalar quantum field theories in de Sitter space-time. The first one is specific to de Sitter …

The Euclidean or Bunch-Davies O (4, 1) invariant state for quantum fields in global de Sitter
space is shown to be unstable to small perturbations, even for a massive free field with no …