Records from the S-Matrix Marathon: A Timeless History of Time
Mang Hei Gordon Lee, Enrico Pajer, Mathieu Giroux, Holmfridur S., Hannesdottir, Sebastian Mizera, Celina Pasiecznik

TL;DR
This paper reviews recent advances in understanding cosmological correlators through various formalisms, effective theories, and symmetry principles, aiming to deepen insights into quantum gravity via cosmological observations.
Contribution
It introduces the in-out formalism, explores effective theories in curved spacetime, and summarizes symmetry-based properties of the wavefunction, offering new tools for quantum cosmology research.
Findings
Development of the in-out formalism and recursion relations
Construction of effective theories using open quantum systems
Identification of symmetry constraints on the wavefunction
Abstract
By directly probing the initial conditions of our universe, cosmological surveys offer us a unique observational handle on quantum field theory in curved spacetime with dynamical gravity and might even allow us to glean information about a full theory of quantum gravity. Here we report on recent progress to study the natural observables in the problem, namely cosmological correlators. After setting the stage, we review results from three different approaches. First, we present the in-out formalism as an interesting alternative to the well-known in-in formalism and stress some of its advantages, such as the derivation of recursion relations, correlators cutting rules and a proposal for a de Sitter scattering matrix. Second, we tackle the important open problem of constructing effective theories in curved spacetime, which generally requires an open quantum system approach. Third, we…
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Taxonomy
TopicsNoncommutative and Quantum Gravity Theories · Black Holes and Theoretical Physics · Cosmology and Gravitation Theories
