This book offers the first comprehensive introduction to a new research direction in fundamental physics that seeks to understand the origin and evolution of the universe. It brings together perspectives and tools from four distinct areas: quantum open systems, scattering amplitudes in particle physics, de Sitter physics, and disordered systems in statistical mechanics.

In particular, it explores the open system approach to simple effective field theories, inflation, gauge theory and gravity, and the construction of quantum field theories in expanding universes. Topics include the Landau analysis of Feynman integrals in both particle physics and cosmology, the structure of Hilbert spaces in curved spacetimes, and the interplay between Lorentzian and Euclidean formulations of computables. The book also delves into the physics of the glass transition, with a detailed treatment of spin glass models and their relevance to understanding the state space in cosmology, highlighting how disorder and complexity inform our grasp of the universe’s large-scale behavior.

Based on lectures delivered by leading experts at the summer school The Disordered Universe 2025, held in As Barreiras (Castro Caldelas, Spain) from 21 July to 01 August 2025, the book is designed for graduate students and early-career researchers. Each chapter includes both the lecture content and accompanying tutorial sessions, providing a pedagogical and hands-on approach to the material.
Readers are expected to have a foundational understanding of quantum field theory, general relativity, cosmology, complex analysis, and statistical physics. By integrating diverse theoretical frameworks, this book opens new pathways for exploring cosmological phenomena and offers a valuable resource for those interested in the frontiers of theoretical physics.

Paolo Benincasa earned a PhD in theoretical physics and applied mathematics from the University of Western Ontario in Canada. He then held research positions at several universities across Europe, including Durham (UK), Santiago de Compostela (Spain) as a Juan de la Cierva Fellow, and IFT-UAM/CSIC in Madrid. He later became an assistant professor at the Niels Bohr Institute in Denmark, joined the IFT-UAM/CSIC as junior faculty through the Atracción de Talento program, and worked as a senior scientist at the Max Planck Institute for Physics in Germany.
His research has focused on fundamental physics. He was the first to calculate the bulk viscosity of strongly coupled plasmas, contributed to understanding particle physics phenomena using basic principles, and developed a geometric-combinatorial framework to describe early-universe cosmological processes. This work also advanced the study of mathematical structures known as polytopes.

Guilherme Pimentel completed his PhD in theoretical physics at Princeton University under the supervision of Juan Maldacena. He held postdoctoral positions at the University of Cambridge, the University of Amsterdam, and the University of Leiden before taking on his current role.
His research includes pioneering studies, alongside Maldacena, on non-Gaussianities caused by gravitational waves during cosmic inflation. He is also one of the founders of the cosmological bootstrap program and helped adapt a method originally used for particle physics—based on differential equations for Feynman integrals—to cosmological applications.