Cosmological production of dark matter in the Universe and in the laboratory

TL;DR

This thesis explores how quantum fields in curved spacetimes can produce dark matter particles during cosmic inflation and demonstrates how Bose-Einstein condensate experiments can simulate and analyze these phenomena.

Contribution

It provides a comprehensive framework linking cosmological particle production with laboratory analogs, offering new methods to study dark matter generation and quantum effects in curved backgrounds.

Findings

Scalar and vector fields can produce dark matter via inflationary mechanisms.

Bose-Einstein condensate experiments can simulate cosmological particle production.

Analog experiments can measure entanglement and reconstruct expansion histories.

Abstract

This thesis investigates cosmological particle production within Quantum Field Theory in Curved Spacetimes, both as a dark matter mechanism and through analog simulations using Bose-Einstein condensates. While a full theory of Quantum Gravity remains elusive, studying quantum fields on curved backgrounds provides essential insights into the early Universe. We focus on how dynamical spacetimes, particularly during inflation, generate particles from spectator fields influenced solely by geometry. The work is divided into four parts. Part I establishes the theoretical framework, covering cosmology, inflation, and the principles of analog gravity. Part II analyzes particle production in various inflationary models, showing that scalar and vector fields can account for observed dark matter abundance, especially through tachyonic instabilities. Part III explores BEC experiments, mapping phonons to scalar fields in expanding universes. We demonstrate the reconstruction of expansion histories, reinterpret production as a scattering problem, and propose methods to measure entanglement between produced pairs. Finally, Part IV addresses quantum vacuum ambiguities and the impact of non-adiabatic transitions during the "switch-on" and "switch-off" of expansion. Ultimately, this work highlights the viability of cosmological particle production for dark matter and the power of analog experiments to enhance our understanding of quantum effects in curved spacetimes.