The quantum physics of chronology protection

Abstract

This is a brief survey of the current status of Stephen Hawking's ``chronology protection conjecture''. That is: ``Why does nature abhor a time machine?'' I'll discuss a few examples of spacetimes containing ``time machines'' (closed causal curves), the sorts of peculiarities that arise, and the reactions of the physics community. While pointing out other possibilities, this article concentrates on the possibility of ``chronology protection''. As Stephen puts it: ``It seems that there is a Chronology Protection Agency which prevents the appearance of closed timelike curves and so makes the universe safe for historians.''

CUP style: uses cmmp.cls; 18 pages; contribution to "The future of theoretical physics and cosmology", conference in honour of Professor Stephen Hawking on the occasion of his 60'th birthday. V2: Some references added

References in corpus (2)

• Towards the observation of Hawking radiation in Bose--Einstein condensates
• Lorentzian 3d Gravity with Wormholes via Matrix Models

Cited by in corpus (15)

• Analogue Gravity
• Morris-Thorne wormholes with a cosmological constant
• Nut Charged Space-times and Closed Timelike Curves on the Boundary
• Formation of closed timelike curves in a composite vacuum/dust asymptotically-flat spacetime
• Signature change events: A challenge for quantum gravity?
• Closed Timelike Curves and Holography in Compact Plane Waves
• Closed timelike curves in asymmetrically warped brane universes
• The Weak Gravity Conjecture Requires the Existence of Exotic AdS Black Holes
• Cosmic Censorship for AdS${}_5$-Kerr
• The Topology of Branching Universes
• Neutrino time travel
• Classical and semi-classical energy conditions
• Quantum superpositions of the speed of light
• Tractor beams, pressor beams, and stressor beams in general relativity
• Chronology protection in stationary 3D spacetimes