Weak Energy Condition Violation and Superluminal Travel

Crawford, Paulo

doi:10.1007/3-540-36973-2_15

Cited by 46 publications

(38 citation statements)

References 21 publications

(34 reference statements)

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“…and so equals the energy density measured by the Eulerian observers, that is, equation (11). It is easy to verify that the energy density is distributed in a toroidal region around the z-axis, in the direction of travel of the warp bubble [23].…”

Section: Warp Drive Basicsmentioning

confidence: 99%

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Fundamental limitations on ‘warp drive’ spacetimes

Lobo

Visser

2004

Class. Quantum Grav.

117

111

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"Warp drive" spacetimes are useful as "gedanken-experiments" that force us to confront the foundations of general relativity, and among other things, to precisely formulate the notion of "superluminal" communication. After carefully formulating the Alcubierre and Natário warp drive spacetimes, and verifying their non-perturbative violation of the classical energy conditions, we consider a more modest question and apply linearized gravity to the weak-field warp drive, testing the energy conditions to first and second order of the warp-bubble velocity, v. Since we take the warpbubble velocity to be non-relativistic, v ≪ c, we are not primarily interested in the "superluminal" features of the warp drive. Instead we focus on a secondary feature of the warp drive that has not previously been remarked upon -the warp drive (if it could be built) would be an example of a "reaction-less drive". For both the Alcubierre and Natário warp drives we find that the occurrence of significant energy condition violations is not just a high-speed effect, but that the violations persist even at arbitrarily low speeds.A particularly interesting feature of this construction is that it is now meaningful to think of placing a finite mass spaceship at the centre of the warp bubble, and then see how the energy in the warp field compares with the mass-energy of the spaceship. There is no hope of doing this in Alcubierre's original version of the warp-field, since by definition the point in the centre of the warp bubble moves on a geodesic and is "massless". That is, in Alcubierre's original formalism and in the Natário formalism the spaceship is always treated as a test particle, while in the linearized theory we can treat the spaceship as a finite mass object. For both the Alcubierre and Natário warp drives we find that even at low speeds the net (negative) energy stored in the warp fields must be a significant fraction of the mass of the spaceship.

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Section: Warp Drive Basicsmentioning

confidence: 99%

“…In fact, numerous solutions to the Einstein field equations are now known that allow "effective" superluminal travel [2,3,4,5,6,7,8,9,10,11]. Despite the use of the term superluminal, it is not "really" possible to travel faster than light, in any local sense.…”

Section: Introductionmentioning

confidence: 99%

Fundamental limitations on ‘warp drive’ spacetimes

Lobo

Visser

2004

Class. Quantum Grav.

117

111

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“…For CTC space-time, the matter-energy sources must be realistic, that is, the stressenergy tensor must be known type of matter fields which satisfy the different energy conditions. Many known CTC space-time, for examples the traversable wormholes [18,19], and the warp drive models [20][21][22] violate the weak energy condition (WEC), which states that T μν U μ U ν ≥ 0 for a time-like tangent vector field U μ , that is, the energy-density must be non-negative. The CTC space-time in [23] violate the strong energy condition (SEC), which states that [24]).…”

Section: Introductionmentioning

confidence: 99%

A type N radiation field solution with $$\Lambda <0$$ Λ < 0 in a curved space-time and closed time-like curves

Ahmed

2018

Eur. Phys. J. C

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An anti-de Sitter background four-dimensional type N solution of the Einstein's field equations, is presented. The matter-energy content pure radiation field satisfies the null energy condition (NEC), and the metric is free-from curvature divergence. In addition, the metric admits a nonexpanding, non-twisting and shear-free geodesic null congruence which is not covariantly constant. The space-time admits closed time-like curves which appear after a certain instant of time in a causally well-behaved manner. Finally, the physical interpretation of the solution, based on the study of the equation of the geodesics deviation, is analyzed.

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“…The presence of such curves in a spacetime violates the causality condition. Examples of these spacetime are the Gödel's Cosmological solution [1], van Stockum solution [2], Tipler's rotating cylinder [3], traversable wormholes [4,5], and the wrap dripe models [6,7] violate the weak energy condition (WEC), Gott's solution [8], Krasnikov spacetime [9], electrovac spacetime [10], and pure radiation field spacetimes [11,12,13,14] have CTCs. Some well-known vacuum spacetimes such as the Kerr and KerrNewmann black holes solution [15,16] (see also [17]), NUT-Taub metric [18], Bonnor metric [19,20], Ori metric [21], locally isometric AdS metric [22], and type N Einstein spacetime [23] have CTCs.…”

Section: Introductionmentioning

confidence: 99%

A Type D Non-Vacuum Spacetime with Causality Violating Curves, and Its Physical Interpretation

Ahmed¹

2017

Commun. Theor. Phys.

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We present a topologically trivial, non-vacuum solution of the Einstein's field equations in four-dimensions, which is regular everywhere. The metric admits circular closed timelike curves, which appear beyond the null curve, and these timelike curves are linearly stable under linear perturbations. Additionally, the spacetime admits null geodesics curve which are not closed, and the metric is of type D in the Petrov classification scheme. The stress-energy tensor anisotropic fluid satisfy the different energy conditions and a generalization of Equation-of-State parameter of perfect fluid p = ω ρ. The metric admits a twisting, shearfree, non-exapnding timelike geodesic congruence. Finally, the physical interpretation of this solution, based on the study of the equation of the geodesics deviation, will be presented.

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Weak Energy Condition Violation and Superluminal Travel

Cited by 46 publications

References 21 publications

Fundamental limitations on ‘warp drive’ spacetimes

Fundamental limitations on ‘warp drive’ spacetimes

A type N radiation field solution with $$\Lambda <0$$ Λ < 0 in a curved space-time and closed time-like curves

A Type D Non-Vacuum Spacetime with Causality Violating Curves, and Its Physical Interpretation

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