The Creation of Particles in an Expanding Universe

TL;DR

This thesis introduces the concept of particle creation in an expanding universe, a fundamental phenomenon linking gravitation and quantum theory, and highlights its historical significance in physics.

Contribution

It provides a foundational analysis of particle creation by gravitational fields, a key insight in the interplay between gravity and quantum mechanics.

Findings

Particle creation occurs in expanding universes.

The phenomenon is crucial for understanding quantum effects in cosmology.

The work established a basis for subsequent research in quantum field theory in curved spacetime.

Abstract

This document is the Ph.D. thesis of Leonard Parker, submitted to Harvard University in 1966. Over the decades, several generations of physicists have been introduced to the concept of particle creation by gravitational fields, a phenomenon that has become a cornerstone in exploring the interplay between gravitation and quantum theory. Yet, the foundational breakthrough that led to the prediction and understanding of this phenomenon remains unfamiliar to many. In the interest of historical accuracy and in recognition of a seminal contribution to physics, the thesis has been retyped and made it freely available as an open-access (arXiv) document. The reissued thesis is accompanied by a Foreword that places the work in its proper historical context. As the team responsible for this new edition, we (Antonio Ferreiro, Jos\'e Navarro-Salas, and Silvia Pla) hope that future generations will continue to draw inspiration from this pioneering text.