Year: 2026
Type: preprint
Abstract: Effective field theories (EFTs) offer a powerful method to unify diverse models under a small set of control parameters, allowing systematic expansions around well-established theories. While these techniques were traditionally developed for particle physics experiments with clean, isolated initial states, realistic macroscopic environments are often noisy and dissipative. Recognising the limitations of traditional EFTs has recently sparked intense progress at the interface of high-energy physics and condensed matter. These developments motivate a new approach to gravitation and cosmology, one that models the gravitational sector as evolving in the presence of an unobservable medium. Open Effective Field Theories provide a systematic, controllable framework for this endeavour. This chapter presents this versatile framework and illustrates how the Schwinger-Keldysh formalism captures the influence of unknown environments, manifesting as dissipation and noise, on observational probes. These notes are based on a series of lectures held during the La Ricotta Summer School "The Disordered Universe 2025" from 21 July to 1 August 2025.
Source: arXiv (Cornell University)
Institutions: Institute for Theoretical Physics Amsterdam, University of Amsterdam, University of Cambridge, Scuola Normale Superiore, École Polytechnique Fédérale de Lausanne, Centre National de la Recherche Scientifique, Université Paris Cité, Laboratoire AstroParticule et Cosmologie, Universidade de Santiago de Compostela
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: Xunta de Galicia
OpenAlex ID: W7224098651