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- Chemissany, W., et al.
(författare)
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Black holes in supergravity and integrability
- 2010
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :9, s. 80-
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Tidskriftsartikel (refereegranskat)abstract
- Stationary black holes of massless supergravity theories are described by certain geodesic curves on the target space that is obtained after dimensional reduction over time. When the target space is a symmetric coset space we make use of the group-theoretical structure to prove that the second order geodesic equations are integrable in the sense of Liouville, by explicitly constructing the correct amount of Hamiltonians in involution. This implies that the Hamilton-Jacobi formalism can be applied, which proves that all such black hole solutions, including non-extremal solutions, possess a description in terms of a (fake) superpotential. Furthermore, we improve the existing integration method by the construction of a Lax integration algorithm that integrates the second order equations in one step instead of the usual two step procedure. We illustrate this technology with a specific example.
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| 2. |
- Chemissany, W., et al.
(författare)
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Brane solutions and integrability: a status report
- 2011
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Konferensbidrag (refereegranskat)abstract
- We review the status of the integrability and solvability of the geodesics equations of motion on symmetric coset spaces that appear as sigma models of supergravity theories when reduced over respectively the timelike and spacelike direction. Such geodesic curves describe respectively timelike and spacelike brane solutions. We emphasize the applications to black holes.
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| 3. |
- Habiba, M, et al.
(författare)
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Caesarean section on request: a comparison of obstetricians' attitudes in eight European countries
- 2006
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Ingår i: BJOG: An International Journal of Obstetrics & Gynaecology. - : Wiley. - 1471-0528 .- 1470-0328. ; 113:6, s. 647-656
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Tidskriftsartikel (refereegranskat)abstract
- Objective To explore the attitudes of obstetricians to performe a caesarean section on maternal request in the absence of medical indication. Design Cluster sampling cross-sectional survey. Setting Neonatal Intensive Care Unit (NICU) associated maternity units in eight European countries. Population Obstetricians with at least 6 months clinical experience. Methods NICU-associated maternity units were chosen by census in Luxembourg, Netherlands and Sweden and by geographically stratified random sampling in France, Germany, Italy, Spain and UK. An anonymous, self-administered questionnaire was used for data collection. Main outcome measures Obstetricians' willingness to perform a caesarean section on maternal request. Results One hundred and five units and 1530 obstetricians participated in the study (response rates of 70 and 77%,respectively). Compliance with a hypothetical woman's request for elective caesarean section simply because it was 'her choice' was lowest in Spain (15%), France (19%) and Netherlands (22%); highest in Germany (75%) and UK (79%) and intermediate in the remaining countries. Using weighted multivariate logistic regression, country of practice (P < 0.001), fear of litigation (P = 0.004) and working in a university-affiliated hospital (P = 0.001) were associated with physicians' likelihood to agree to patient's request. The subset of female doctors with children was less likely to agree (OR 0.29, 95% CI 0.20-0.42). Conclusions The differences in obstetricians' attitudes are not founded on concrete medical evidence. Cultural factors, legal liability and variables linked to the specific perinatal care organisation of the various countries play a role. Greater emphasis should be placed on understanding the motivation, values and fears underlying a woman's request for elective caesarean delivery.
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