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1.
  • Andréasson, Håkan, 1955-, et al. (författare)
  • Comments on the paper ‘Static solutions of the Vlasov–Einstein system’ by G. Wolansky
  • 2019
  • Ingår i: Archive for Rational Mechanics and Analysis. - 1432-0673 .- 0003-9527.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this note we address the attempted proof of the existence of static solutions to the Einstein–Vlasov system as given in Wolansky (Arch Ration Mech Anal 156:205–230, 2001). We focus on a specific and central part of the proof which concerns a variational problem with an obstacle. We show that two important claims in Wolansky (2001) are incorrect and we question the validity of a third claim. We also discuss the variational problem and its difficulties with the aim of stimulating further investigation of this intriguing problem in particular answering the question of whether or not static solutions of the Einstein–Vlasov system can be found as local minimizers of an energy-Casimir functional.
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2.
  • Hall, Sara, et al. (författare)
  • Accuracy of a panel of 5 cerebrospinal fluid biomarkers in the differential diagnosis of patients with dementia and/or parkinsonian disorders.
  • 2012
  • Ingår i: Archives of neurology. - 1538-3687. ; 69:11, s. 1445-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: To assess the ability of 5 cerebrospinal fluid (CSF) biomarkers to differentiate between common dementia and parkinsonian disorders. Design: A cross-sectional, clinic-based study. Participants: Cerebrospinal fluid samples (N=453) were obtained from healthy individuals serving as controls and from patients with Parkinson disease (PD), PD with dementia (PDD), dementia with Lewy bodies (DLB), Alzheimer disease (AD), progressive supranuclear palsy (PSP), multiple system atrophy (MSA), or corticobasal degeneration (CBD). Setting: Neurology and memory disorder clinics. Main Outcome Measures: Cerebrospinal fluid biomarker levels in relation to clinical diagnosis. Results: Cerebrospinal fluid levels of alpha-synuclein were decreased in patients with PD, PDD, DLB, and MSA but increased in patients with AD. Cerebrospinal fluid levels of beta-amyloid 1-42 were decreased in DLB and even further decreased in AD. Cerebrospinal fluid levels of total tau and hyperphosphorylated tau were increased in AD. Multivariate analysis revealed that these biomarkers could differentiate AD from DLB and PDD with an area under the curve of 0.90, with alpha-synuclein and total tau contributing most to the model. Cerebrospinal fluid levels of neurofilament light chain were substantially increased in atypical parkinsonian disorders (ie, PSP, MSA, and CBD), and multivariate analysis revealed that the level of neurofilament light chain alone could differentiate PD from atypical parkinsonian disorders, with an area under the curve of 0.93. Conclusions: Ascertainment of the alpha-synuclein level in CSF somewhat improves the differential diagnosis of AD vs DLB and PDD when combined with established AD biomarkers. The level of neurofilament light chain alone may differentiate PD from atypical parkinsonian disorders.
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4.
  • Ames, Ellery, et al. (författare)
  • Cosmic string and black hole limits of toroidal Vlasov bodies in general relativity
  • 2019
  • Ingår i: Physical Review D : covering particles, fields, gravitation, and cosmology. - AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 99:2
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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.</p>
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5.
  • Ames, E., et al. (författare)
  • Cosmic string and black hole limits of toroidal Vlasov bodies in general relativity
  • 2019
  • Ingår i: Physical Review D. - 2470-0010. ; 99:2
  • 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.
6.
  • Ames, Ellery, et al. (författare)
  • On axisymmetric and stationary solutions of the self-gravitating Vlasov system
  • 2016
  • Ingår i: Classical and Quantum Gravity. - 0264-9381. ; 33:15
  • 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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7.
  • Andreasson, Bengt Håkan, 1955- (författare)
  • Bilens minskade attraktionskraft
  • 2006
  • Ingår i: Vardagslivets fronter. - Göteborg : Arkipelag. - 91-85838-70-5
  • Bokkapitel (övrigt vetenskapligt)
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10.
  • Andreasson, Håkan, 1966-, et al. (författare)
  • A numerical investigation of the stability of steady states and critical phenomena for the spherically symmetric Einstein–Vlasov system
  • 2006
  • Ingår i: Classical and Quantum Gravity. ; 23, s. 3659-3677
  • Tidskriftsartikel (refereegranskat)abstract
    • The stability features of steady states of the spherically symmetric EinsteinVlasov system are investigated numerically. We find support for the conjecture by Zel'dovich and Novikov that the binding energy maximum along a steady state sequence signals the onset of instability, a conjecture which we extend to and confirm for non-isotropic states. The sign of the binding energy of a solution turns out to be relevant for its time evolution in general. We relate the stability properties to the question of universality in critical collapse and find that for Vlasov matter universality does not seem to hold.
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