| 1. |
- Ames, Ellery, et al.
(författare)
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Cosmic string and black hole limits of toroidal Vlasov bodies in general relativity
- 2019
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 99:2
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Tidskriftsartikel (refereegranskat)abstract
- We numerically investigate limits of a two-parameter family of stationary solutions to the Einstein-Vlasov system. The solutions are toroidal and have nonvanishing angular momentum. As the parameters are tuned to more relativistic solutions (measured e.g., by an increasing redshift) we provide evidence for a sequence of solutions which approaches the extreme Kerr black hole family. Solutions with angular momentum larger than the square of the mass are also investigated, and in the relativistic limit the near-field geometry of such solutions is observed to become locally rotationally symmetric about the matter density. The existence of a deficit angle in these regions is investigated.
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| 2. |
- Ames, Ellery, 1984, et al.
(författare)
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On axisymmetric and stationary solutions of the self-gravitating Vlasov system
- 2016
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 33:15
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Tidskriftsartikel (refereegranskat)abstract
- Axisymmetric and stationary solutions are constructed to the Einstein-Vlasov and Vlasov-Poisson systems. These solutions are constructed numerically, using finite element methods and a fixed-point iteration in which the total mass is fixed at each step. A variety of axisymmetric stationary solutions are exhibited, including solutions with toroidal, disk-like, spindle-like, and composite spatial density configurations, as are solutions with non-vanishing net angular momentum. In the case of toroidal solutions, we show for the first time, solutions of the Einstein-Vlasov system which contain ergoregions.
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| 3. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Models for Self-Gravitating Photon Shells and Geons
- 2017
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Ingår i: Annales Henri Poincare. - : Springer Science and Business Media LLC. - 1424-0637 .- 1424-0661. ; 18:2, s. 681-705
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Tidskriftsartikel (refereegranskat)abstract
- We prove existence of spherically symmetric, static, self-gravitating photon shells as solutions to the massless Einstein-Vlasov system. The solutions are highly relativistic in the sense that the ratio 2m(r) / r is close to 8 / 9, where m(r) is the Hawking mass and r is the area radius. In 1955 Wheeler constructed, by numerical means, so-called idealized spherically symmetric geons, i.e., solutions of the Einstein-Maxwell equations for which the energy momentum tensor is spherically symmetric on a time average. The structure of these solutions is such that the electromagnetic field is confined to a thin shell for which the ratio 2m / r is close to 8 / 9, i.e., the solutions are highly relativistic photon shells. The solutions presented in this work provide an alternative model for photon shells or idealized spherically symmetric geons.
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| 4. |
- Andreasson, Håkan, 1966, et al.
(författare)
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On the rotation curves for axially symmetric disk solutions of the Vlasov-Poisson system
- 2015
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 446:4, s. 3932-3942
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Tidskriftsartikel (refereegranskat)abstract
- A large class of flat axially symmetric solutions to the Vlasov–Poisson system is constructed with the property that the corresponding rotation curves are approximately flat, slightly decreasing or slightly increasing. The rotation curves are compared with measurements from real galaxies and satisfactory agreement is obtained. These facts raise the question whether the observed rotation curves for disc galaxies may be explained without introducing dark matter. Furthermore, it is shown that for the ansatz we consider stars on circular orbits do not exist in the neighbourhood of the boundary of the steady state.
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| 5. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Proof of the cosmic no-hair conjecture in the T-3-Gowdy symmetric Einstein-Vlasov setting
- 2016
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Ingår i: Journal of the European Mathematical Society. - : European Mathematical Society - EMS - Publishing House GmbH. - 1435-9863 .- 1435-9855. ; 18:7, s. 1565-1650
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Tidskriftsartikel (refereegranskat)abstract
- The currently preferred models of the universe undergo accelerated expansion induced by dark energy. One model for dark energy is a positive cosmological constant. It is consequently of interest to study Einstein's equations with a positive cosmological constant coupled to matter satisfying the ordinary energy conditions: the dominant energy condition etc. Due to the difficulty of analysing the behaviour of solutions to Einstein's equations in general, it is common to either study situations with symmetry, or to prove stability results. In the present paper, we do both. In fact, we analyse, in detail, the future asymptotic behaviour of T-3-Gowdy symmetric solutions to the Einstein-Vlasov equations with a positive cosmological constant. In particular, we prove the cosmic no-hair conjecture in this setting. However, we also prove that the solutions are future stable (in the class of all solutions). Some of the results hold in a more general setting. In fact, we obtain conclusions concerning the causal structure of T-2-symmetric solutions, assuming only the presence of a positive cosmological constant, matter satisfying various energy conditions and future global existence. Adding the assumption of T-3-Gowdy symmetry to this list of requirements, we obtain C-0-estimates for all but one of the metric components. There is consequently reason to expect that many of the results presented in this paper can be generalised to other types of matter.
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| 6. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Proof of the cosmic no-hair conjecture in the T-3-Gowdy symmetric Einstein-Vlasov setting
- 2016
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Ingår i: Journal of the European Mathematical Society. - : EMS Publishing House. - 1435-9855 .- 1435-9863. ; 18:7, s. 1565-1650
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Tidskriftsartikel (refereegranskat)abstract
- The currently preferred models of the universe undergo accelerated expansion induced by dark energy. One model for dark energy is a positive cosmological constant. It is consequently of interest to study Einstein's equations with a positive cosmological constant coupled to matter satisfying the ordinary energy conditions: the dominant energy condition etc. Due to the difficulty of analysing the behaviour of solutions to Einstein's equations in general, it is common to either study situations with symmetry, or to prove stability results. In the present paper, we do both. In fact, we analyse, in detail, the future asymptotic behaviour of T-3-Gowdy symmetric solutions to the Einstein-Vlasov equations with a positive cosmological constant. In particular, we prove the cosmic no-hair conjecture in this setting. However, we also prove that the solutions are future stable (in the class of all solutions). Some of the results hold in a more general setting. In fact, we obtain conclusions concerning the causal structure of T-2-symmetric solutions, assuming only the presence of a positive cosmological constant, matter satisfying various energy conditions and future global existence. Adding the assumption of T-3-Gowdy symmetry to this list of requirements, we obtain C-0-estimates for all but one of the metric components. There is consequently reason to expect that many of the results presented in this paper can be generalised to other types of matter.
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| 7. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Static solutions to the Einstein-Vlasov system with a nonvanishing cosmological constant
- 2015
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Ingår i: SIAM Journal on Mathematical Analysis. - : Society for Industrial & Applied Mathematics (SIAM). - 0036-1410 .- 1095-7111 .- 1095-7154. ; 47:4, s. 2657-2688
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Tidskriftsartikel (refereegranskat)abstract
- We construct spherically symmetric static solutions to the Einstein-Vlasov system with nonvanishing cosmological constant Λ. The results are divided as follows. For small Λ > 0 we show the existence of globally regular solutions which coincide with the Schwarzschild-deSitter solution in the exterior of the matter regions. For Λ < 0 we show via an energy estimate the existence of globally regular solutions which coincide with the Schwarzschild-anti-deSitter solution in the exterior vacuum region. We also construct solutions with a Schwarzschild singularity at the center regardless of the sign of Λ. For all solutions considered, the energy density and the pressure components have bounded support. Finally, we point out a straightforward method for obtaining a large class of global, nonvacuum spacetimes with topologies ℝ × S3 and ℝ × S2 × ℝ which arise from our solutions as a result of using the periodicity of the Schwarzschild-deSitter solution. A subclass of these solutions contains black holes of different masses.
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| 8. |
- Bjersand, Kathrine, et al.
(författare)
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Drug Sensitivity Testing in Cytoreductive Surgery and Intraperitoneal Chemotherapy of Pseudomyxoma Peritonei
- 2015
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Ingår i: Annals of Surgical Oncology. - : Springer Science and Business Media LLC. - 1068-9265 .- 1534-4681. ; 22, s. S810-S816
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Cytoreductive surgery (CRS) and intraperitoneal chemotherapy (IPC) is an established therapy for pseudomyxoma peritonei (PMP). However, the role of IPC is unclear. By ex vivo assessment of PMP tumor cell sensitivity to cytotoxic drugs, we investigated the basis for IPC drug selection and the role of IPC in the management of PMP.METHODS: Tumor cells were prepared by collagenase digestion of tumor tissue from 133 PMP patients planned for CRS and IPC. Tumor cell sensitivity to oxaliplatin, 5FU, mitomycin C, doxorubicin, irinotecan, and cisplatin was assessed in a 72-h cell-viability assay. Drug sensitivity was correlated to progression-free survival (PFS) and overall survival (OS).RESULTS: Samples from 92 patients were analyzed successfully. Drug sensitivity varied considerably between samples. Peritoneal mucinous carcinomatosis (PMCA), compared with PMCA intermediate or disseminated peritoneal adenomucinosis, was slightly more resistant to platinum and 5FU and tumor cells from patients previously treated with chemotherapy were generally less sensitive than those from untreated patients. Multivariate analysis showed patient performance status and completeness of CRS to be prognostic for OS. Among patients with complete CRS (n = 61), PFS tended to be associated with sensitivity to mitomycin C and cisplatin (p ≈ 0.06). At the highest drug concentration tested, the hazard ratio for disease relapse increased stepwise with drug resistance for all drugs.CONCLUSIONS: Ex vivo assessment of drug sensitivity in PMP provides prognostic information. The results suggest a role for IPC as therapeutic adjunct to CRS and for individualization of IPC by pretreatment assessment of drug sensitivity.
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| 9. |
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| 10. |
- Nilsson, Tony, et al.
(författare)
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Effects on Alcohol Consumption and Alcohol Related Harm of a Community-Based Prevention Intervention With National Support in Sweden
- 2018
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Ingår i: Substance Use & Misuse. - : Informa UK Limited. - 1082-6084 .- 1532-2491. ; 53:3, s. 412-419
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Tidskriftsartikel (refereegranskat)abstract
- Background: In order to strengthen local alcohol prevention work in Sweden the Swedish government has for the past almost 15years commissioned the Public Health Agency of Sweden to initiate a series of community-based alcohol prevention projects. The latest of these, labeled local development with ambitions (LUMA), included 25 municipalities in Sweden. Objectives: Aim of this study is to examine if LUMA municipalities that received financial support, with requirements, increased local alcohol prevention and if alcohol consumption and harm declined. Methods: Twenty-five Swedish municipalities that received financial support aiming to strengthen local alcohol preventing activities (intervention group) were compared to municipalities that did not receive such support (control group, N = 224), before, during, and after the intervention period. Two composite measures of policy and activity were created and used. The composite activity measure includes seven activity indicators and the composite policy measure includes six policy indicators. Harm measures have been selected based on several recommended indicators for monitoring alcohol, tobacco, and other drugs in Sweden. A fixed effects model was used to analyze data. Results: The results reveal that prevention activities increased and several alcohol-related harm indicators were reduced in intervention municipalities (LUMA) compared with in control municipalities. Conclusions: It seems as if financial support, combined with specific requirements and support from the regional and national level, can stimulate local alcohol prevention activities and have a significant effect on alcohol consumption and alcohol-related harm. Similar evaluations in other countries would be of great value for assessing the generalizability of findings.
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