Chronology protection conjecture

Journal Article · Wed Jul 15 00:00:00 EDT 1992 · Physical Review, D (Particles Fields); (United States)

DOI:https://doi.org/10.1103/PhysRevD.46.603· OSTI ID:7184545

Hawking, S W ^[1]

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1. Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB39EW (United Kingdom)

It has been suggested that an advanced civilization might have the technology to warp spacetime so that closed timelike curves would appear, allowing travel into the past. This paper examines this possibility in the case that the causality violations appear in a finite region of spacetime without curvature singularities. There will be a Cauchy horizon that is compactly generated and that in general contains one or more closed null geodesics which will be incomplete. One can define geometrical quantities that measure the Lorentz boost and area increase on going round these closed null geodesics. If the causality violation developed from a noncompact initial surface, the averaged weak energy condition must be violated on the Cauchy horizon. This shows that one cannot create closed timelike curves with finite lengths of cosmic string. Even if violations of the weak energy condition are allowed by quantum theory, the expectation value of the energy-momentum tensor would get very large if timelike curves become almost closed. It seems the back reaction would prevent closed timelike curves from appearing. These results strongly support the chronology protection conjecture: {ital The} {ital laws} {ital of} {ital physics} {ital do} {ital not} {ital allow} {ital the} {ital appearance} {ital of} {ital closed} {ital timelike} {ital curves}.

• OSTI ID: 7184545
• Journal Information: Physical Review, D (Particles Fields); (United States), Vol. 46:2; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
QUANTUM GRAVITY
SPACE-TIME
CAUSALITY
COSMOLOGY
EINSTEIN FIELD EQUATIONS
ENERGY DENSITY
ENERGY-MOMENTUM TENSOR
LIGHT CONE
QUANTUM FIELD THEORY
STRING MODELS
VACUUM POLARIZATION
COMPOSITE MODELS
EQUATIONS
EXTENDED PARTICLE MODEL
FIELD EQUATIONS
FIELD THEORIES
MATHEMATICAL MODELS
PARTICLE MODELS
QUARK MODEL
TENSORS
662110* - General Theory of Particles & Fields- Theory of Fields & Strings- (1992-)