Classical theories of time travel

Albert Einstein’s general theory of relativity is a geometric theory of gravitation which seeks to describe the effective mutual attraction between entities that possess mass. Within this theory, there exists an interesting class of objects called closed timelike curves (CTCs). Such objects are fascinating because a particle moving along one may travel back in time and interact with its past self, and so the geometries that permit the formation of CTCs are often colloquially known as time machines. It is because of this self-interaction that fictional depictions of time travel have captivated the interest of the public for more than a century, while both the validity and implications of the phenomenon have continually been discussed in the scientific literature.

Contents

• Closed timelike curves and time machines
  • Wormhole-based time machines
• Time-travel paradoxes
  • The principle of self-consistency
• The Cauchy problem on spacetimes containing CTCs
• Time-travelling billiard balls
  • Indeterministic dynamics and evolution multiplicity
  • Quantum resolutions to classical indeterminism