| 1. |
- Bengtsson, Ingemar, et al.
(author)
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What are extremal Kerr Killing vectors up to?
- 2012
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In: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 29:21
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Journal article (peer-reviewed)abstract
- In the extremal Kerr spacetime the horizon Killing vector field is null on a timelike hypersurface crossing the horizon at a fixed latitude and spacelike on both sides of the horizon in the equatorial plane. We explain in some detail how this behavior is consistent with the existence of timelike Killing vectors everywhere off the horizon, and how it arises in a limit from the Kerr spacetime where there is a similar hypersurface strictly outside the horizon.
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| 2. |
- Bengtsson, Ingemar, et al.
(author)
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Where are the Trapped Surfaces?
- 2010
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In: J. Phys. Conf. Ser. Vol. 229. - : IOP Publishing. ; , s. 012004-
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Conference paper (peer-reviewed)abstract
- We discuss the boundary of the spacetime region through each point of which a trapped surface passes, first in some simple soluble examples, and then in the self-similar Vaidya solution. For the latter the boundary must lie strictly inside the event horizon. We present a class of closed trapped surfaces extending strictly outside the apparent horizon
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| 3. |
- Hjern, Anders, et al.
(author)
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East africans in Sweden have a high risk for type 1 diabetes
- 2012
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In: Diabetes Care. - Alexandria, USA : American Diabetes Association. - 0149-5992 .- 1935-5548. ; 35:3, s. 597-598
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Journal article (peer-reviewed)abstract
- Citing this article BMJ Open October 31, 2013 3:e003418Objective: To investigate the prevalence of type 1 diabetes in children with an origin inSub-Saharan Africa in Sweden.Research design and methods: Nationwide register study based on retrievedprescriptions of insulin during 2009 in children aged 0–18 years. The study population consistedof 35,756 children in families with an origin in Sub-Saharan Africa and 1,666,051 children withnative Swedish parents.Results: The odds ratio (OR) for insulin medication in Swedish-born children in familiesoriginating in East Africa was 1.29 (95% CI 1.02–1.63) compared with offspring of nativeSwedish parents, after adjustment for age and sex, and less common in children who themselveswere born in East Africa: 0.50 (0.34–0.73). Offspring of parents from other parts of Sub-SaharanAfrica had a comparatively low risk for insulin medication.Conclusions: This study indicates that Swedish-born children with an origin in EastAfrica have a high risk of type 1 diabetes.
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| 4. |
- Pidokrajt, Narit, 1979-, et al.
(author)
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Geometry of black hole thermodynamics
- 2003
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In: General Relativity and Gravitation. - Germany : Springer. - 0001-7701 .- 1572-9532. ; 35:10, s. 1733-1743
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Journal article (peer-reviewed)abstract
- The Hessian of the entropy function can be thought of as a metric tensor on the state space. In the context of thermodynamical fluctuation theory Ruppeiner has argued that the Riemannian geometry of this metric gives insight into the underlying statistical mechanical system; the claim is supported by numerous examples. We study this geometry for some families of black holes. It is flat for the BTZ and Reissner-Nordstrom black holes, while curvature singularities occur for the Reissner-Nordstrom-anti-de Sitter and Kerr black holes.
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| 5. |
- Pidokrajt, Narit, 1979-, et al.
(author)
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On Geometro-thermodynamics of dilaton black holes
- 2008
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In: EAS Publications Series. - France : EDP Sciences 2008. - 1638-1963. ; 30, s. 279-283
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Journal article (peer-reviewed)abstract
- In this talk we present the latest results from our ongoing project on geometro-thermodynamics (also known as information geometry of thermodynamics or Ruppeiner geometry) of dilaton BHs in 4D in both Einstein and string frames and a dyonic dilaton BH and at the end we report very briefly results from this approach to the 2D dilaton BHs.
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| 6. |
- Söderström, Ulf, 1947-, et al.
(author)
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Being born in Sweden increases the risk for type 1 diabetes : a study of migration of children to Sweden as a natural experiment
- 2012
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In: Acta Paediatrica. - West Sussex, United Kingdom : Wiley-Blackwell. - 0803-5253 .- 1651-2227. ; 101:1, s. 73-77
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Journal article (peer-reviewed)abstract
- Aim: To investigate whether the age of first exposure to a high-incidence country like Sweden determines the risk of T1DM in children with an origin in a low incidence region of the world.Methods: Register study in a Swedish study population in the age 6–25 years in three categories of residents with an origin in low incidence regions of T1DM (Eastern Europe, East Asia, South Asia and Latin America); 24 252 international adoptees; 47 986 immigrants and 40 971 Swedish-born with two foreign-born parents and a comparison group of 1 770 092 children with Swedish-born parents. Retrieval of a prescription of insulin during 2006 was used as an indicator of T1DM and analysed with logistic regression.Results: The odds ratios (OR) for T1DM were lower than the Swedish majority population for residents with an origin in the four low incidence regions. Being Swedish-born implied a higher risk for T1DM in the four low incidence study groups compared with the internationally adopted with an OR of 1.68 (CI 1.03–2.73).Conclusions: Being born in Sweden increases the risk for T1DM in children with an origin in low incidence countries. This may imply that exposures in utero or very early infancy are important risk factors for T1DM
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| 7. |
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| 8. |
- Åman, Jan E., et al.
(author)
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Flat information geometries in black hole thermodynamics
- 2006
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In: General Relativity and Gravitation. - : Springer Science and Business Media LLC. - 0001-7701 .- 1572-9532. ; 38:8, s. 1305-1315
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Journal article (peer-reviewed)abstract
- The Hessian of either the entropy or the energy function can be regarded as a metric on a Gibbs surface. For two parameter families of asymptotically flat black holes in arbitrary dimension one or the other of these metrics are flat, and the state space is a flat wedge. The mathematical reason for this is traced back to the scale invariance of the Einstein–Maxwell equations. The picture of state space that we obtain makes some properties such as the occurence of divergent specific heats transparent.
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| 9. |
- Åman, Jan E., et al.
(author)
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Geometry of higher-dimensional black hole thermodynamics
- 2006
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In: Physical Review D. Particles and fields. - 0556-2821 .- 1089-4918. ; 73:2, s. 024017-
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Journal article (peer-reviewed)abstract
- We investigate thermodynamic curvatures of the Kerr and Reissner-Nordström (RN) black holes in spacetime dimensions higher than four. These black holes possess thermodynamic geometries similar to those in four-dimensional spacetime. The thermodynamic geometries are the Ruppeiner geometry and the conformally related Weinhold geometry. The Ruppeiner geometry for a d=5 Kerr black hole is curved and divergent in the extremal limit. For a d>=6 Kerr black hole there is no extremality but the Ruppeiner curvature diverges where one suspects that the black hole becomes unstable. The Weinhold geometry of the Kerr black hole in arbitrary dimension is a flat geometry. For the RN black hole the Ruppeiner geometry is flat in all spacetime dimensions, whereas its Weinhold geometry is curved. In d>=5 the Kerr black hole can possess more than one angular momentum. Finally we discuss the Ruppeiner geometry for the Kerr black hole in d=5 with double angular momenta.
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| 10. |
- Åman, Jan E., et al.
(author)
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Ruppeiner theory of black hole thermodynamics
- 2007
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In: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 66, s. 012007-
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Journal article (peer-reviewed)abstract
- The Ruppeiner metric as determined by the Hessian of the Gibbs surface provides a geometric description of thermodynamic systems in equilibrium. An interesting example is a black hole in equilibrium with its own Hawking radiation. In this article, we present results from the Ruppeiner study of various black hole families from different gravity theories e.g. 2D dilaton gravity, BTZ, general relativity and higher-dimensional Einstein-Maxwell gravity.
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