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Upcoming events in Mathematics

(previous see here)
Mon 22/01/18 15:00
Fulton G20
Mathematics Seminar
Prof. Georgios Akrivis (University of Ioannina)
Stability of implicit and implicit–explicit multistep methods for nonlinear parabolic equations in Hilbert spaces
abstract

Abstract

We consider the discretization of a class of nonlinear parabolic equations in Hilbert spaces by both implicit and implicit–explicit multistep methods, and establish lo- cal stability under best possible and best possible linear stability conditions, respectively. Our approach is based on a spectral and Fourier stability technique and uses a suitable quantification of the non-self-adjointness of linear elliptic operators as well as a discrete perturbation argument

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Mon 29/01/18 14:00
Fulton G20
Mathematics Seminar
Dr. Peter Stewart (University of Galsgow)
(Themes: Mathematical Biology, Continuum Mechanics)
Mon 05/02/18 14:00
Fulton G20
Mathematics Seminar
Dr. Sergey Anfinogentov (University of Warwick)
Analysis of low-amplitude oscillations in solar corona by motion magnification
Mon 12/02/18 14:00
Fulton G20
Mathematics Seminar
Dr. Stephen Metcalfe (University of York)
Approximating Blow-up Via A Posteriori Error Estimation
abstract

Abstract

The numerical approximation of blow-up (singularities which develop in solutions to certain differential equations) is a difficult problem due to the high temporal and spatial resolution needed close to the singularity; this necessitates the design of special numerical methods for this class of problem. Indeed, many such numerical methods have been designed but they often make quite restrictive assumptions. Additionally, there is no rigorous way of knowing whether the resulting computations from existing methods are quantitatively reasonable. In this talk, I will discuss recent developments in an alternative approach to the approximation of such problems which is based on a posteriori error estimation. In principle, providing such error bounds are well-behaved close to the singularity, this will allow us to select the computational parameters (time steps, mesh sizes) in our numerical method as well as provide the secondary advantage of giving a quantitative bound on the size of the error.

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Mon 26/02/18 14:00
Fulton G20
Mathematics Seminar
Prof. Duncan Mackay (University of St Andrews)
Helicity condensation and the solar cycle
abstract

Abstract

Solar filaments exhibit a global chirality pattern that is closely related to the injection and transport of magnetic helicity across the Sun. Dextral/sinistral filaments, corresponding to negative/positive magnetic helicity dominant in the northern/southern hemisphere. This pattern is inconsistent with the sign of magnetic helicity injected by differential rotation along East-West orientated polarity inversion lines. To investigate the origin of this hemispheric pattern in realistic magnetic field configurations, a global evolution model along with a large-scale representation of helicity condensation is applied. Periods in both the rising and declining-phase of the solar cycle are simulated. In the helicity condensation model positive/negative values of the vorticity of the convective cells is used in the northern/southern hemisphere to inject negative/positive helicity. The magnitude of the vorticity is then varied as a free parameter. To reproduce the correct percentage relationship between the dominant and minority filament chirality in each hemisphere, a vorticity of magnitude 2. 5e−6 s−1 is required. This rate is however insufficient to produce the 16 correct unimodal profile of chirality with latitude. To achieve this, a vorticity of 5e−6 s−1 or higher is needed. This places a lower limit on the magnitude of the vorticity in the helicity condensation model, such that it can dominate over differential rotation and reproduce the observed hemispheric pattern. Future observational studies need to establish if such a consistent vorticity pattern of this magnitude exists within convective cells across all latitudes of the Sun.

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Mon 12/03/18 14:00
Fulton G20
Mathematics Seminar
Dr. Thomas Elsden (University of St Andrews)
(Themes: MHD)
Mon 19/03/18 14:00
Fulton G20
Mathematics Seminar
Prof. Andrew Gilbert (University of Exeter)
(Themes: MHD)
Mon 26/03/18 14:00
Fulton G20
Mathematics Seminar
Prof. Miguel Onorato (Università di Torino)
(Themes: Nonlinear waves)
Mon 07/05/18 14:00
Fulton G20
Mathematics Seminar
Dr. Carlo Mercuri (University of Swansea)
(Themes: Partial Differential Equations)