skip to content

IMAGES

a network for developers and users of imaging and analysis tools
 

Thu 18 Jan 15:00: TBA

Talks - Mon, 08/01/2024 - 10:49
TBA

Abstract not available

Add to your calendar or Include in your list

Thu 18 Jan 15:00: TBA

Other events - Mon, 08/01/2024 - 10:49
TBA

Abstract not available

Add to your calendar or Include in your list

Thu 08 Feb 15:00: Towards Finite Element Tensor Calculus

Talks - Mon, 08/01/2024 - 10:46
Towards Finite Element Tensor Calculus

Finite Element Exterior Calculus (FEEC) provides a cohomology framework for structure-preserving discretisation of a large class of PDEs. There has been a relatively mature FEEC theory with de Rham complexes for problems involving differential forms (skew-symmetric tensors) and vector fields. A canonical discretisation exists, which has a discrete topological interpretation and can be generalized to other discrete structures, e.g., graph cohomology.

In recent years, there has been significant interest in extending FEEC to tensor-valued problems with applications in continuum mechanics, differential geometry and general relativity etc. In this talk, we first review the de Rham sequences and their canonical discretisation with Whitney forms. Then we provide an overview of some efforts towards Finite Element Tensor Calculus (FETC). On the continuous level, we characterise tensors and differential structures using the Bernstein-Gelfand-Gelfand (BGG) machinery and incorporate analysis. On the discrete level in 2D and 3D, we discuss analogies of the Whitney forms and establish their cohomology. A special case is Christiansen’s finite element interpretation of Regge calculus, a discrete geometric scheme for metric and curvature. Moreover, we present a correspondence between BGG sequences, continuum mechanics with microstructure and Riemann-Cartan geometry. These efforts are in the direction of establishing a tensor calculus on triangulation and potentially on other discrete structures.

Add to your calendar or Include in your list

Thu 08 Feb 15:00: Towards Finite Element Tensor Calculus

Other events - Mon, 08/01/2024 - 10:46
Towards Finite Element Tensor Calculus

Finite Element Exterior Calculus (FEEC) provides a cohomology framework for structure-preserving discretisation of a large class of PDEs. There has been a relatively mature FEEC theory with de Rham complexes for problems involving differential forms (skew-symmetric tensors) and vector fields. A canonical discretisation exists, which has a discrete topological interpretation and can be generalized to other discrete structures, e.g., graph cohomology.

In recent years, there has been significant interest in extending FEEC to tensor-valued problems with applications in continuum mechanics, differential geometry and general relativity etc. In this talk, we first review the de Rham sequences and their canonical discretisation with Whitney forms. Then we provide an overview of some efforts towards Finite Element Tensor Calculus (FETC). On the continuous level, we characterise tensors and differential structures using the Bernstein-Gelfand-Gelfand (BGG) machinery and incorporate analysis. On the discrete level in 2D and 3D, we discuss analogies of the Whitney forms and establish their cohomology. A special case is Christiansen’s finite element interpretation of Regge calculus, a discrete geometric scheme for metric and curvature. Moreover, we present a correspondence between BGG sequences, continuum mechanics with microstructure and Riemann-Cartan geometry. These efforts are in the direction of establishing a tensor calculus on triangulation and potentially on other discrete structures.

Add to your calendar or Include in your list

Mon 11 Mar 18:00: Using organoids to reveal what sets the human brain apart Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Talks - Tue, 02/01/2024 - 09:58
Using organoids to reveal what sets the human brain apart

The human brain sets us apart as a species, yet how it develops and functions differently to that of other mammals is still largely unclear. This also makes it difficult to understand how disorders of the brain arise, and therefore how to treat them. To understand such a complex organ, we have developed cerebral organoids, or brain organoids, 3D brain tissues made from stem cells that mimic the fetal brain. Such organoids are allowing us to tackle questions previously impossible with more traditional approaches. Indeed, our recent findings provide insight into various factors that influence the developing brain, and how the human brain becomes so uniquely large enabling our special cognitive abilities.

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Add to your calendar or Include in your list

Wed 06 Mar 18:00: HONORARY FELLOWS LECTURE - Every breath you take and every move you make - understanding cellular oxygen sensing mechanisms Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Talks - Tue, 02/01/2024 - 09:53
HONORARY FELLOWS LECTURE - Every breath you take and every move you make - understanding cellular oxygen sensing mechanisms

The maintenance of oxygen homeostasis is a key physiological challenge, inadequate oxygen (hypoxia) being a major component of most human diseases. The lecture will trace insights into human oxygen homeostasis from the founding work of William Harvey on the circulation of the blood to the molecular elucidation of a system of oxygen sensing that functions to measure oxygen levels in cells and control adaptive responses to hypoxia. The lecture will outline how the oxygen sensitive signal is generated by a set of ‘oxygen splitting’ enzymes that modify a transcription factor (HIF) to signal for its degradation (and hence inactivation). It will attempt to illustrate and rationalise the unexpected in biological discovery and discuss the interface of discovery science with the development of medical therapeutics.

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Add to your calendar or Include in your list

Mon 26 Feb 18:00: The quest for the first stars and first black holes with the James Webb Space Telescope Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Talks - Tue, 02/01/2024 - 09:50
The quest for the first stars and first black holes with the James Webb Space Telescope

Finding and understanding the nature of the first stars at cosmic dawn is one of the most important and most ambitious goals for modern astrophysics. The first populations of stars produced the first chemical elements heavier than helium and formed the first, small protogalaxies, which then evolved, across the cosmic epoch, into the large and mature galaxies, such as the Milky Way and those in our local neighbour. Equally important and equally challenging is the search, in the early Universe, of the seeds of the first population of black holes, which later evolved in the supermassive black holes at the centre of galaxies, with masses even exceeding a billion times the mass of the Sun. When matter accretes on such supermassive black holes it can become so luminous to vastly outshine the light emitted by all stars in their host galaxy.

Since its launch, about two years ago, the James Webb Space Telescope has been revolutionizing this area of research. Its sensitivity in detecting infrared light from the remotest parts of the Universe is orders of magnitude higher than any previous observatory, an historical leap in astronomy and, more broadly, in science. I will presents some of the first, extraordinary discoveries from the Webb telescope, which have resulted in several unexpected findings. I will also discuss the new puzzles and areas of investigation that have been opened by Webb’s observations, how these challenge theoretical models, and the prospects of further progress in the coming years.

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Add to your calendar or Include in your list

Mon 12 Feb 18:00: Going beyond emissions reduction – Climate Repair Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Talks - Tue, 02/01/2024 - 09:49
Going beyond emissions reduction – Climate Repair

The lecture will firstly summarise exactly where we are with climate change and crucially what the scientists are now considering in terms of the future. A future based purely on emissions reductions cannot keep the world below 1.5C.

We discuss some of the exciting ideas for greenhouse gas removal, and importantly going beyond terrestrial-based carbon dioxide removal. We will explore some of the approaches for marine carbon dioxide removal as well as the development of materials to accelerate the rate of oxidation of methane.

We will then spend time discussing what additional options we might have beyond emissions reduction and greenhouse gas removal; whilst these are necessary, even the most optimistic and ambitious scenarios considered by the IPCC indicate that they are not sufficient to keep temperatures below 1.5C. We will therefore review engineering concepts to limit temperature rise or interventions to protect glaciers and sea-ice, and ostensibly buy us time to stave off the worst effects of climate change whilst we get greenhouse gas levels down.

We will explore the different technologies which are being researched at the University of Cambridge in collaboration with multiple partner universities around the world, as well as the issues of public attitudes, governance and ethics associated with such research and potential deployment.

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Add to your calendar or Include in your list

Mon 29 Jan 18:00: G I TAYLOR LECTURE - Volcanic eruptions and magma flows Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Talks - Tue, 02/01/2024 - 09:48
G I TAYLOR LECTURE - Volcanic eruptions and magma flows

Abstract not available

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Add to your calendar or Include in your list

Thu 30 Nov 15:00: CANCELLED

Talks - Thu, 30/11/2023 - 10:12
CANCELLED

By a basic linear algebra result, a family of two or more commuting symmetric matrices has a common eigenvector basis and can thus be jointly diagonalized. Such joint eigenvalue problems come in several flavors and they play an important role in a variety of applications, including independent component analysis in signal processing, multivariate polynomial systems, tensor decompositions, and computational quantum chemistry. Perhaps surprisingly, the development of robust numerical algorithms for solving such problems is by no means trivial. To start with, roundoff error or other forms of error will inevitably destroy commutativity assumptions. In turn, one can at best hope to find approximate solutions to joint eigenvalue problems and, in turn, most existing approaches are based on optimization techniques, which may or may not recover the approximate solution. In this talk, we propose randomized methods that address joint eigenvalue problems via the solution of one or a few standard eigenvalue problems. The methods are simple but surprisingly effective. We provide a theoretical explanation for their success by establishing probabilistic guarantees for robust recovery. Through numerical experiments on synthetic and real-world data, we show that our algorithms reach or outperform state-of-the-art optimization-based methods. This talk is based on joint work with Haoze He.

Add to your calendar or Include in your list

Thu 30 Nov 15:00: CANCELLED

Other events - Thu, 30/11/2023 - 10:12
CANCELLED

By a basic linear algebra result, a family of two or more commuting symmetric matrices has a common eigenvector basis and can thus be jointly diagonalized. Such joint eigenvalue problems come in several flavors and they play an important role in a variety of applications, including independent component analysis in signal processing, multivariate polynomial systems, tensor decompositions, and computational quantum chemistry. Perhaps surprisingly, the development of robust numerical algorithms for solving such problems is by no means trivial. To start with, roundoff error or other forms of error will inevitably destroy commutativity assumptions. In turn, one can at best hope to find approximate solutions to joint eigenvalue problems and, in turn, most existing approaches are based on optimization techniques, which may or may not recover the approximate solution. In this talk, we propose randomized methods that address joint eigenvalue problems via the solution of one or a few standard eigenvalue problems. The methods are simple but surprisingly effective. We provide a theoretical explanation for their success by establishing probabilistic guarantees for robust recovery. Through numerical experiments on synthetic and real-world data, we show that our algorithms reach or outperform state-of-the-art optimization-based methods. This talk is based on joint work with Haoze He.

Add to your calendar or Include in your list

Thu 23 Nov 15:00: Pseudospectra: Two Different Ways

Talks - Mon, 20/11/2023 - 14:01
Pseudospectra: Two Different Ways

I will talk about how pseudospectra comes up in two different ways in my research. Firstly, I will talk the certification and computation of pseudospectra for a non-self-adjoint linear operator. Efficient calculation of the pseudospectrum for unbounded operators in infinite dimensional spaces is a relatively unexplored territory. Often finite-dimensional subspaces are used in place of the infinite dimensional space. However, the use of finite dimensional subspaces changes the qualitative nature of pseudospectral contours from unbounded curves with asymptotic behaviour at infinity to closed loops. The overlap between these curves forms the well-resolved of the pseudospectrum. It is useful to have a certification process for these calculated points. Secondly, I will talk about more recent work in using pseudospectra to model the HPA axis. Pseudospectra can be obtained via creating models or via data driven approaches. I will discuss the pros and cons of these different methods, which include interpretability and matching to experimental data.

Add to your calendar or Include in your list

Thu 23 Nov 15:00: Pseudospectra: Two Different Ways

Other events - Mon, 20/11/2023 - 14:01
Pseudospectra: Two Different Ways

I will talk about how pseudospectra comes up in two different ways in my research. Firstly, I will talk the certification and computation of pseudospectra for a non-self-adjoint linear operator. Efficient calculation of the pseudospectrum for unbounded operators in infinite dimensional spaces is a relatively unexplored territory. Often finite-dimensional subspaces are used in place of the infinite dimensional space. However, the use of finite dimensional subspaces changes the qualitative nature of pseudospectral contours from unbounded curves with asymptotic behaviour at infinity to closed loops. The overlap between these curves forms the well-resolved of the pseudospectrum. It is useful to have a certification process for these calculated points. Secondly, I will talk about more recent work in using pseudospectra to model the HPA axis. Pseudospectra can be obtained via creating models or via data driven approaches. I will discuss the pros and cons of these different methods, which include interpretability and matching to experimental data.

Add to your calendar or Include in your list

Mon 20 Nov 18:00: The quiet AI revolution in weather forecasting Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Talks - Thu, 16/11/2023 - 17:54
The quiet AI revolution in weather forecasting

Abstract: Over the last 18 months a quiet AI revolution has begun in the field of numerical weather prediction. Medium-term weather prediction involves forecasting several days to a couple of weeks in the future and these forecasts are critical for making many social and economic decisions. The standard approach to this problem is to run detailed global simulations of the earth’s atmosphere using a supercomputer, so-called numerical weather prediction (NWP). As little as one year ago, researchers in this field had thought it unlikely that machine learning approaches would be competitive with numerical weather prediction any time soon. However, over the last year, the same advances that underpin large language models, like ChatGPT, have been applied to weather prediction. Surprisingly, these models achieve a performance which is already competitive with standard NWP , but with a computational cost that is 1000s of times cheaper. The deep learning based forecasts have also been shown to be surprisingly robust, performing reasonably even when faced with rare or extreme events. Consequently, weather prediction centres like the World Meteorological Organisation and the European Centre for Medium-Range Weather Forecasts (ECMWF) are now racing to build machine learning teams and publicly testing AI forecasts. This talk will describe this quieter AI revolution and it will end with a discussion of the opportunities for AI and machine learning in weather and climate, and speak a little more widely about the balancing act that must be struck between regulation and adoption of AI technology.

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

Add to your calendar or Include in your list

Thu 30 Nov 15:00: Randomized methods for joint eigenvalue problems

Talks - Mon, 13/11/2023 - 17:13
Randomized methods for joint eigenvalue problems

By a basic linear algebra result, a family of two or more commuting symmetric matrices has a common eigenvector basis and can thus be jointly diagonalized. Such joint eigenvalue problems come in several flavors and they play an important role in a variety of applications, including independent component analysis in signal processing, multivariate polynomial systems, tensor decompositions, and computational quantum chemistry. Perhaps surprisingly, the development of robust numerical algorithms for solving such problems is by no means trivial. To start with, roundoff error or other forms of error will inevitably destroy commutativity assumptions. In turn, one can at best hope to find approximate solutions to joint eigenvalue problems and, in turn, most existing approaches are based on optimization techniques, which may or may not recover the approximate solution. In this talk, we propose randomized methods that address joint eigenvalue problems via the solution of one or a few standard eigenvalue problems. The methods are simple but surprisingly effective. We provide a theoretical explanation for their success by establishing probabilistic guarantees for robust recovery. Through numerical experiments on synthetic and real-world data, we show that our algorithms reach or outperform state-of-the-art optimization-based methods. This talk is based on joint work with Haoze He.

Add to your calendar or Include in your list

Thu 30 Nov 15:00: Randomized methods for joint eigenvalue problems

Other events - Mon, 13/11/2023 - 17:13
Randomized methods for joint eigenvalue problems

By a basic linear algebra result, a family of two or more commuting symmetric matrices has a common eigenvector basis and can thus be jointly diagonalized. Such joint eigenvalue problems come in several flavors and they play an important role in a variety of applications, including independent component analysis in signal processing, multivariate polynomial systems, tensor decompositions, and computational quantum chemistry. Perhaps surprisingly, the development of robust numerical algorithms for solving such problems is by no means trivial. To start with, roundoff error or other forms of error will inevitably destroy commutativity assumptions. In turn, one can at best hope to find approximate solutions to joint eigenvalue problems and, in turn, most existing approaches are based on optimization techniques, which may or may not recover the approximate solution. In this talk, we propose randomized methods that address joint eigenvalue problems via the solution of one or a few standard eigenvalue problems. The methods are simple but surprisingly effective. We provide a theoretical explanation for their success by establishing probabilistic guarantees for robust recovery. Through numerical experiments on synthetic and real-world data, we show that our algorithms reach or outperform state-of-the-art optimization-based methods. This talk is based on joint work with Haoze He.

Add to your calendar or Include in your list