20 September sees the Climate Protest come to Oxford. Whatever your view of the tactics the fact is that the University itself produces regular research on the impact of meat consumption on climate and health and is launching a wide campaign on sustainability over the next few weeks (#TruePlanet).
Dark Matter, Modified Gravity - Or What?
Abstract
In this talk I will explain (a) what observations speak for the
hypothesis of dark matter, (b) what observations speak for
the hypothesis of modified gravity, and (c) why it is a mistake
to insist that either hypothesis on its own must
explain all the available data. The right explanation, I will argue,
is instead a suitable combination of dark matter and modified
gravity, which can be realized by the idea that dark matter
has a superfluid phase.
Gauged sigma models and magnetic skyrmions
Abstract
Magnetic skyrmions are topological solitons which occur in a large class
of ferromagnetic materials and which are currently attracting much
attention in the condensed matter community because of their possible
use in future magnetic information storage technology. The talk is
about an integrable model for magnetic skyrmions, introduced in a recent
paper (arxiv 1812.07268) and generalised in (arxiv 1905.06285). The
model can be solved by interpreting it as a gauged nonlinear sigma
model. In the talk will explain the model and the geometry behind its
integrability, and discuss some of the solutions and their physical
interpretation.
Ranks of cubic surfaces
Abstract
There are various notions of rank, which measure the complexity of a tensor or polynomial. Cubic surfaces can be viewed as symmetric tensors. We consider the non-symmetric tensor rank and the symmetric Waring rank of cubic surfaces, and show that the two notions coincide over the complex numbers. The results extend to order three tensors of all sizes, implying the equality of rank and symmetric rank when the symmetric rank is at most seven. We then explore the connection between the rank of a polynomial and the singularities of its vanishing locus, and we find the possible singular loci of a cubic surface of given rank. This talk is based on joint work with Eunice Sukarto.
The brain's waterscape
Short bio:
Marie E. Rognes is Chief Research Scientist and Research Professor in Scientific Computing and Numerical Analysis at Simula Research Laboratory, Oslo, Norway. She received her Ph.D from the University of Oslo in 2009 with an extended stay at the University of Minneapolis, Twin Cities, Minneapolis, US. She has been at Simula Research Laboratory since 2009, led its Department for Biomedical Computing from 2012-2016 and currently leads a number of research projects focusing on mathematical modelling and numerical methods for brain mechanics including an ERC Starting Grant in Mathematics. She won the 2015 Wilkinson Prize for Numerical Software, the 2018 Royal Norwegian Society of Sciences and Letters Prize for Young Researchers within the Natural Sciences, and was a Founding Member of the Young Academy of Norway.
Abstract
Your brain has its own waterscape: whether you are reading or sleeping, fluid flows around or through the brain tissue and clears waste in the process. These physiological processes are crucial for the well-being of the brain. In spite of their importance we understand them but little. Mathematics and numerics could play a crucial role in gaining new insight. Indeed, medical doctors express an urgent need for modeling of water transport through the brain, to overcome limitations in traditional techniques. Surprisingly little attention has been paid to the numerics of the brain’s waterscape however, and fundamental knowledge is missing. In this talk, I will discuss mathematical models and numerical methods for the brain's waterscape across scales - from viewing the brain as a poroelastic medium at the macroscale and zooming in to studying electrical, chemical and mechanical interactions between brain cells at the microscale.