The refractive index of curved spacetime II: QED, Penrose limits and black holes

Hollowood, Timothy J.; Shore, Graham M.; Stanley, Ross James

doi:10.1088/1126-6708/2009/08/089

Cited by 39 publications

(85 citation statements)

References 41 publications

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“…As demonstrated in our previous investigations of the realisation of causality in curved spacetime [5][6][7][8][9][10], in order to verify that causality is respected we need to demonstrate that the phase velocity, which may be superluminal for low frequencies, is equal to 1 in the high-frequency limit [5,[11][12][13]. This implies constraints on the phase shift of the photon modes as they scatter from the shockwave.…”

Section: Jhep03(2016)129mentioning

confidence: 99%

“…This is technically simpler than its spinor counterpart, although the necessary formalism for the latter is established in [8]. In section 8, we also discuss a super-renormalizable scalar theory, which exhibits interesting differences from QED in its UV behaviour.…”

Section: Jhep03(2016)129mentioning

confidence: 99%

“…One of the main insights of our previous work [5][6][7][8][9][10], is that, as long as m σ (the transverse curvature scale), we may approximate the geometry in the vicinity of the chosen ray with its associated Penrose limit geometry. This is illustrated in figure 8.…”

Section: Photon-shockwave Scatteringmentioning

confidence: 99%

“…before the shockwave is reached. 15 Notice that, if we assume the scale of derivatives of the curvature is of the same order as the curvature itself, the expansion parameter here is ω √ R/m 2 [8,13] where R is a typical curvature component. This is the parameter ωσ/m 2 for the shockwave.…”

Section: The Beam Shockwavementioning

confidence: 99%

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Causality violation, gravitational shockwaves and UV completion

Hollowood

Shore

2016

J. High Energ. Phys.

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The effective actions describing the low-energy dynamics of QFTs involving gravity generically exhibit causality violations. These may take the form of superluminal propagation or Shapiro time advances and allow the construction of "time machines", i.e. spacetimes admitting closed non-spacelike curves. Here, we discuss critically whether such causality violations may be used as a criterion to identify unphysical effective actions or whether, and how, causality problems may be resolved by embedding the action in a fundamental, UV complete QFT. We study in detail the case of photon scattering in an Aichelburg-Sexl gravitational shockwave background and calculate the phase shifts in QED for all energies, demonstrating their smooth interpolation from the causality-violating effective action values at low-energy to their manifestly causal high-energy limits. At low energies, these phase shifts may be interpreted as backwards-in-time coordinate jumps as the photon encounters the shock wavefront, and we illustrate how the resulting causality problems emerge and are resolved in a two-shockwave time machine scenario. The implications of our results for ultra-high (Planck) energy scattering, in which graviton exchange is modelled by the shockwave background, are highlighted.

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Section: Jhep03(2016)129mentioning

confidence: 99%

Section: Jhep03(2016)129mentioning

confidence: 99%

Section: Photon-shockwave Scatteringmentioning

confidence: 99%

Section: The Beam Shockwavementioning

confidence: 99%

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Causality violation, gravitational shockwaves and UV completion

Hollowood

Shore

2016

J. High Energ. Phys.

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“…The breakthrough made in a series of papers [8][9][10][11] was to extend the DrummondHathrell result by relaxing the requirement that ω 2 R/m 4 ≪ 1. The result is obtained by calculating the one-loop vacuum polarization due to the Feynman graphs illustrated in Figure 1 in the appropriate limits.…”

Section: Introductionmentioning

confidence: 99%

Graviton propagation and vacuum polarization in curved space

Stanley

Hollowood

2011

J. High Energ. Phys.

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The effects of vacuum polarization arising from loops of massive scalar particles on graviton propagation in curved space are considered. Physically, they are due to curvature induced tidal forces acting on the cloud of virtual scalar particles surrounding the graviton. The effects are tractable in a WKB and large mass limit and the results can be written as an effective refractive index for the graviton modes with both a real and imaginary part. The imaginary part of the refractive index is a curvature induced contribution to the wavefunction renormalization of the graviton in real affine time and can have the effect of dressing or un-dressing the graviton. The real part of the refractive index increases logarithmically at high frequency as long as the null energy condition is satisfied by the background.

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Antihydrogen and Fundamental Physics

Charlton¹,

Eriksson²,

Shore³

2020

SpringerBriefs in Physics

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The recent advent of high precision antihydrogen (H) spectroscopy opens the way to stringent experimental tests of the fundamental principles underlying particle physics and general relativity (GR), such as Lorentz and CPT invariance and the Einstein Equivalence Principle (EEP), on pure antimatter systems. In this paper, the nature and implications of these tests is investigated, with special reference to the ALPHA antihydrogen programme at CERN. This is underpinned by a theoretical review of the role of antiparticles, causality and fundamental symmetries in relativistic quantum field theory (QFT) and the theory of time measurement in GR. Low-energy effective theories which break Lorentz and CPT symmetry, or the Strong Equivalence Principle (SEP), are then introduced, together with a review of several 'fifth force' scenarios involving new long-range forces which would effectively violate the universality of free-fall, or Weak Equivalence Principle (WEPff). The possible role of CPT violation in determining the matter-antimatter asymmetry of the Universe is discussed. Explicit calculations are given for the dependence on possible Lorentz and CPT violating couplings of the transition frequencies amongst the 1S, 2S and 2P hyperfine states measured in the magnetic field of the ALPHA trap and the resulting bounds are compared with existing limits. An analysis of the implications for the EEP of current free-fall and spectroscopic measurements with antihydrogen is presented and existing and potential bounds on WEPff and the universality of clocks (WEPc) are derived, together with constraints on fifth forces. Future prospects for high-precision antihydrogen spectroscopy, free-fall and gravitational redshift experiments, and antiatom matter-wave interferometry are described and experimental possibilities involving other antimatter species are briefly outlined.

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The refractive index of curved spacetime II: QED, Penrose limits and black holes

Cited by 39 publications

References 41 publications

Causality violation, gravitational shockwaves and UV completion

Causality violation, gravitational shockwaves and UV completion

Graviton propagation and vacuum polarization in curved space

Antihydrogen and Fundamental Physics

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