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Lectures on Faster-than-Light Travel and Time Travel

by Barak Shoshany

Submission summary

As Contributors: Barak Shoshany
Arxiv Link: (pdf)
Date accepted: 2019-09-17
Date submitted: 2019-09-12 02:00
Submitted by: Shoshany, Barak
Submitted to: SciPost Physics Lecture Notes
Academic field: Physics
  • Gravitation, Cosmology and Astroparticle Physics
  • High-Energy Physics - Theory
Approach: Theoretical


These lecture notes were prepared for a 25-hour course for advanced undergraduate students participating in Perimeter Institute's Undergraduate Summer Program. The lectures cover some of what is currently known about the possibility of superluminal travel and time travel within the context of established science, that is, general relativity and quantum field theory. Previous knowledge of general relativity at the level of a standard undergraduate-level introductory course is recommended, but all the relevant material is included for completion and reference. No previous knowledge of quantum field theory, or anything else beyond the standard undergraduate curriculum, is required. Advanced topics in relativity, such as causal structures, the Raychaudhuri equation, and the energy conditions are presented in detail. Once the required background is covered, concepts related to faster-than-light travel and time travel are discussed. After introducing tachyons in special relativity as a warm-up, exotic spacetime geometries in general relativity such as warp drives and wormholes are discussed and analyzed, including their limitations. Time travel paradoxes are also discussed in detail, including some of their proposed resolutions.

Published as SciPost Phys. Lect. Notes 10 (2019)

List of changes

I have improved the manuscript following the referee report. All of the referee's suggestions have been implemented in full. I added references to the suggested papers. In addition, the chapter on time travel paradoxes has been significantly expanded, including full and detailed treatment of D-CTCs (the quantum version of the multiple timeline solution) and P-CTCs (the quantum version of Novikov's conjecture). No other changes were made except a few minor fixes here and there.

Submission & Refereeing History

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Resubmission 1907.04178v2 on 12 September 2019

Reports on this Submission

Report 1 by Aron Wall on 2019-9-14 Invited Report


The author has taken all my suggestions into consideration, and in particular section 7 is a significantly more detailed and useful resource now. I recommend publication.

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