Keynote Talk - EFTs across the Universe: inflation, dark energy, dark matter, and gravitational waves

• Katsuki Aoki (Yukawa Institute for Theoretical Physics, Kyoto University)

Room: Okochi Hall Our Universe is spatially homogeneous and isotropic on large scales. This high symmetry of the Universe enables us to systematically investigate various possibilities of cosmological scenarios using the powerful tool from high-energy physics, namely, effective field theory (EFT). In this approach, the difference in field contents is translated into the difference in symmetry-breaking patterns, encapsulating phenomenological features of each scenario into effective operators in a model-independent manner. In this talk, starting with a brief review of the so-called EFT of inflation/dark energy, I will talk about how we can extend this framework to different phenomena of cosmology, such as vector dark energy, interacting dark matter and dark energy, and chiral gravitational waves.

Effective field theories of inflationary fluctuations beyond single field and tree level

• Lucas Pinol (LPENS, Paris)

Room: Okochi Hall Effective field theory techniques provide an efficient way to enumerate the allowed operators in various physical systems based on their symmetries. Moreover, they allow for a systematic classification of these operators in decreasing order of relevance based on a derivative expansion. These tools are powerful in guiding us towards the construction of a realistic inflationary scenario with few model assumptions. In this presentation, I will guide the audience towards more general effective field theories of inflationary fluctuations than what is usually considered. In particular, I will show how nonlinearly realised symmetries play a key role in multifield inflation, and I will make the explicit link with the theory for fluctuations in nonlinear sigma models. Finally, I will present a few interesting features at the one-loop level, where symmetries beautifully restore the conservation of the primordial curvature perturbation on super-Hubble scales.

Poster session (with coffee) Room: Okochi Hall

Open system EFT for cosmologists

• Toshifumi Noumi (Tokyo University, Tokyo)

Room: Okochi Hall I will give an introduction to the effective field theory (EFT) of open systems aimed at cosmologists. After motivating why open systems are relevant in cosmology, I will discuss Brownian motion as the simplest illustrative example. I will then present the EFT construction for open systems with spontaneous symmetry breaking and in the presence of gravity, with cosmological applications in mind.

Panel Discussion

• Katsuki Aoki (Yukawa Institute for Theoretical Physics, Kyoto University)
• Lucas Pinol (LPENS, Paris)
• Toshifumi Noumi (Tokyo University, Tokyo)

Room: Okochi Hall