Quantum stability of the time machine

Krasnikov, S.

doi:10.1103/physrevd.54.7322

Cited by 36 publications

(54 citation statements)

References 14 publications

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“…Our only presumption is that both tensors are spherically-symmetric, with h ab given by Eq. (29). The extrinsic curvature will be obtained from the momentum equation (9), and the 3-metric [namely the function g RR (R)] will in turn be derived from the vacuum Energy equation (14).…”

Section: Initial Data For the External Vacuum Regionmentioning

confidence: 99%

Formation of closed timelike curves in a composite vacuum/dust asymptotically flat spacetime

Ori

2007

Phys. Rev. D

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We present a new asymptotically-flat time-machine model made solely of vacuum and dust. The spacetime evolves from a regular spacelike initial hypersurface S and subsequently develops closed timelike curves. The initial hypersurface S is asymptotically flat and topologically trivial. The chronology violation occurs in a compact manner; namely the first closed causal curves form at the boundary of the future domain of dependence of a compact region in S (the core). This central core is empty, and so is the external asymptotically flat region. The intermediate region surrounding the core (the envelope) is made of dust with positive energy density. This model trivially satisfies the weak, dominant, and strong energy conditions. Furthermore it is governed by a well-defined system of field equations which possesses a well-posed initial-value problem.

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Section: Initial Data For the External Vacuum Regionmentioning

confidence: 99%

Formation of closed timelike curves in a composite vacuum/dust asymptotically flat spacetime

Ori

2007

Phys. Rev. D

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“…There still remains, however, the issue of stability . Several analyses [11] [16] [17] indicated possible instabilities of various time-machine solutions to classical perturbations and/or quantum-mechanical fluctuations (see however [18]). Whereas these analyses mostly referred to compactly-generated models, some of the arguments for quantum instabilities apply to noncompactly-generated models as well (see in particular the discussion in [17]).…”

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confidence: 99%

A Class of Time-Machine Solutions with a Compact Vacuum Core

Ori

2005

Phys. Rev. Lett.

125

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We present a class of curved-spacetime vacuum solutions which develope closed timelike curves at some particular moment. We then use these vacuum solutions to construct a time-machine model. The causality violation occurs inside an empty torus, which constitutes the time-machine core. The matter field surrounding this empty torus satisfies the weak, dominant, and strong energy conditions. The model is regular, asymptotically-flat, and topologicallytrivial. Stability remains the main open question.The problem of time-machine formation is one of the outstanding open questions in spacetime physics. Time machines are spacetime configurations including closed timelike curves (CTCs), allowing physical observes to return to their own past. In the presence of a time machine, our usual notion of causality does not hold. The main question is: Do the laws of nature allow, in principle, the creation of a time machine from "normal" initial conditions? (By "normal" I mean, in particular, initial state with no CTCs.)Several types of time-machine models were explored so far. The early proposals include Godel's rotating-dust cosmological model The above models, however, all suffer from one or more severe problems. In some of them [3] [6] the weak energy condition (WEC) [7] is violated, indicating unrealistic matter-energy content. The WEC states that for any physical (timelike) observer the energy density is non-negative, which is the case for all known types of (classical) matter fields. In other models the CTCs are either pre-existing [1] [2] [4] and/or "come from infinity" [4] (see [8] [9]), and/or there is a curvature singularity [2].The only of the above models which does not violate the WEC, and in which CTCs evolve from normal initial data (and within a compact region of space) is that of Ref. [5]. But this model, too, is not satisfactory, for the following reason: The energy-momentum source occupying the time-machine core, though consistent with the WEC (and also with the dominant energy condition [10]), does not fit any known type of matter field. Therefore this configuration (spacetime plus matter) is not a solution of any prescribed set of field equations. Even if we assumed there exist physical matter fields that yield the desired 1

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“…More precisely, Hawking conjectured that the laws of physics prevent local creation of closed timelike curves, as characterized by the existence of a compactly generated Cauchy horizon. In several examples, however, the value of T ren αβ (x) remains finite as the point x approaches the Cauchy horizon [59][60][61][62]. Subsequently Kay, Radzikowski and Wald (KRW) [63] showed that the two-point function, from which the energy-momentum tensor is obtained, is singular, in the sense which will be explained below, for a free scalar field at some points on a compactly generated Cauchy horizon.…”

Section: Quantum Instabilitymentioning

confidence: 99%

Topological censorship and chronology protection

Friedman¹,

Higuchi²

2006

Ann. Phys.

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Over the past two decades, substantial efforts have been made to understand the way in which physics enforces the ordinary topology and causal structure that we observe, from subnuclear to cosmological scales. We review the status of topological censorship and the topology of event horizons; chronology protection in classical and semiclassical gravity; and related progress in establishing quantum energy inequalities.Comment: Dedicated to Rafael Sorkin, whose tutoring and friendship from third grade on is responsible for one of us (JF) having spent his adult life in physics and whose work has inspired both of us. In v.2, some references are updated, and references are added to early work on 2+1 spacetimes and to work on event-horizon topolog

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Quantum stability of the time machine

Cited by 36 publications

References 14 publications

Formation of closed timelike curves in a composite vacuum/dust asymptotically flat spacetime

Formation of closed timelike curves in a composite vacuum/dust asymptotically flat spacetime

A Class of Time-Machine Solutions with a Compact Vacuum Core

Topological censorship and chronology protection

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