| 1. |
- Elvang, Henriette, et al.
(författare)
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On Universality of Ergoregion Mergers
- 2009
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 26:8
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Tidskriftsartikel (refereegranskat)abstract
- We study mergers of ergoregions in d+1-dimensional vacuum gravity. At the merger point, where the ergosurfaces bounding each ergoregion just touch, solutions exhibit universal behavior when there is rotation only in one plane: the angle between the merging ergosurfaces depends only on the symmetries of the solution, not on any other details of the configuration. We show that universality follows from the fact that the relevant component of Einstein's equation reduces to Laplace equation at the point of merger. Thus ergoregion mergers mimic mergers of Newtonian equipotentials and have similar universal behavior. For solutions with rotation in more than one plane, universality is lost. We demonstrate universality and non-universality in several explicit examples.
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| 2. |
- Guica, Monica, et al.
(författare)
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Behind the geon horizon
- 2015
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 32:5
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Tidskriftsartikel (refereegranskat)abstract
- We explore the Papadodimas-Raju prescription for reconstructing the region behind the horizon of one-sided black holes in AdS/CFT in the case of the. P2 geon-a simple, analytic example of a single-sided, asymptotically AdS(3) black hole, which corresponds to a pure CFT state that thermalizes at late times. We show that in this specific example, the mirror operators involved in the reconstruction of the interior have a particularly simple form: the mirror of a single trace operator at late times is just the corresponding single trace operator at early times. We use some explicit examples to explore how changes in the state modify the geometry inside the horizon.
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| 3. |
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| 4. |
- Cabrera Pacheco, A. J., et al.
(författare)
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Asymptotically flat extensions of CMC Bartnik data
- 2017
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Ingår i: Classical and quantum gravity. - : Institute of Physics Publishing. - 0264-9381 .- 1361-6382. ; 34:10
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Tidskriftsartikel (refereegranskat)abstract
- Let g be a metric on the 2-sphere with positive Gaussian curvature and H be a positive constant. Under suitable conditions on (g, H), we construct smooth, asymptotically flat 3-manifolds M with non-negative scalar curvature, with outer-minimizing boundary isometric to and having mean curvature H, such that near infinity M is isometric to a spatial Schwarzschild manifold whose mass m can be made arbitrarily close to a constant multiple of the Hawking mass of . Moreover, this constant multiplicative factor depends only on (g, H) and tends to 1 as H tends to 0. The result provides a new upper bound of the Bartnik mass associated with such boundary data.
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| 5. |
- DEMKIN, P
(författare)
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ON THE STABILITY OF P-BRANE
- 1995
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Ingår i: CLASSICAL AND QUANTUM GRAVITY. - : IOP PUBLISHING LTD. - 0264-9381. ; 12:2, s. 289-296
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Stability of some solutions of the equations of motion of bosonic p-branes in curved and flat spacetimes is stated.
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| 6. |
- Kinney, William H., et al.
(författare)
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The zoo plot meets the swampland : mutual (in)consistency of single-field inflation, string conjectures, and cosmological data
- 2019
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:11
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Tidskriftsartikel (refereegranskat)abstract
- We consider single-field inflation in light of string-motivated 'swampland' conjectures suggesting that effective scalar field theories with a consistent UV completion must have field excursion Delta(phi) less than or similar to M-Pl, in combination with a sufficiently steep potential, MPlV phi/V greater than or similar to O(1). Here, we show that the swampland conjectures are inconsistent with existing observational constraints on single-field inflation. Focusing on the observationally favoured class of concave potentials, we map the allowed swampland region onto the n(S)-r 'zoo plot' of inflationary models, and find that consistency with the Planck satellite and BICEP2/Keck Array requires MPlV phi/V less than or similar to 0.1 and -0.02 less than or similar to M-Pl(2)/V-phi phi < 0, in strong tension with swampland conjectures. Extension to non-canonical models such as DBI Inflation does not significantly weaken the bound.
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| 7. |
- Lindström, Ulf, et al.
(författare)
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Gravitational duality, Palatini variation and boundary terms : a synopsis
- 2023
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Ingår i: Classical and quantum gravity. - : Institute of Physics Publishing (IOPP). - 0264-9381 .- 1361-6382. ; 40:8
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Tidskriftsartikel (refereegranskat)abstract
- We consider f(R) gravity and Born–Infeld–Einstein (BIE) gravity in formulations where the metric and connection are treated independently and integrate out the metric to find the corresponding models solely in terms of the connection, the archetypical treatment being that of Eddington–Schrödinger (ES) duality between cosmological Einstein and Eddington theories. For dimensions , we find that this requires f(R) to have a specific form which makes the model Weyl invariant, and that its Eddington reduction is then equivalent to that of BIE with certain parameters. For D = 2 dimensions, where ES duality is not applicable, we find that both models are Weyl invariant and equivalent to a first order formulation of the bosonic string. We also discuss the form of the boundary terms needed for the variational principle to be well defined on manifolds with non-null boundaries. This requires a modification of the Gibbons–Hawking–York (GHY) boundary term for gravity. This modification also means that the dualities between metric and connection formulations are consistent and include the boundary terms.
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| 8. |
- Lindström, Ulf, et al.
(författare)
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New currents with Killing-Yano tensors
- 2021
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Ingår i: Classical and quantum gravity. - : Institute of Physics Publishing (IOPP). - 0264-9381 .- 1361-6382. ; 38:19
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Tidskriftsartikel (refereegranskat)abstract
- New relations involving the Riemann, Ricci and Einstein tensors that have to hold for a given geometry to admit Killing-Yano tensors (KYTs) are described. These relations are then used to introduce novel conserved 'currents' involving such KYTs. For a particular current based on the Einstein tensor, we discuss the issue of conserved charges and consider implications for matter coupled to gravity. The condition on the background geometry to allow asymptotic conserved charges for a current introduced by Kastor and Traschen is found and a number of other new aspects of this current are commented on. In particular we show that it vanishes for rank (D - 1) KYTs in D dimensions.
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| 9. |
- McCormick, Stephen
(författare)
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On the charged Riemannian Penrose inequality with charged matter
- 2020
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Ingår i: Classical and quantum gravity. - : IOP PUBLISHING LTD. - 0264-9381 .- 1361-6382. ; 37:1
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Tidskriftsartikel (refereegranskat)abstract
- Throughout the literature on the charged Riemannian Penrose inequality, it is generally assumed that there is no charged matter present; that is, the electric field is divergence-free. The aim of this article is to clarify when the charged Riemannian Penrose inequality holds in the presence of charged matter, and when it does not. First we revisit Jang's proof of the charged Riemannian Penrose inequality to show that under suitable conditions on the charged matter, this argument still carries though. In particular, a charged Riemannian Penrose inequality is obtained from this argument when charged matter is present provided that the charge density does not change sign. Moreover, we show that such hypotheses on the sign of the charge are in fact required by constructing counterexamples to the charged Riemannian Penrose inequality when these conditions are violated. We conclude by noting that one of these counterexamples contradicts a version of the charged Penrose inequality existing in the literature, and explain how this existing result can be repaired.
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