CDP

Centre for Dynamical Processes and Structure Formation

Examples of structure formation

Quantum Chemistry - Stochastic Dynamical Systems

Prolate Spheroidal Functions, PSF's are of general interest in many different contexts in physics, like acoustic and electromagnetic scattering, signal processing, antenna analysis, object restoration, image feature descriptions and segmentation, quantum chemistry, quantum technology etc. Generalised PSF's are eigenfunctions of the 2D finite Fourier Transform. They are very important for e.g. spectral estimation of 2D processes and image processing. The equations and the pictures display the underlying definitions and the complex behaviour of the GPSF's. Appropriate substitutions allow new approaches for the time evolution problem comparing filtering and multitapering techniques with respect to accuracy and general effectiveness. General convolution relations offer increased resolution without severe limitations from the uncertainty principle.

Physics - Classical and quantum dynamics of spin systems

Multiscale nonlinear dynamical problems in magnetism.

The dynamics of the magnetization process in real magnets is often governed by defects: impurities, vacancies, grain boundaries, etc. These defects serve as nucleation centers for magnetization reversal or as pinning centers for domain walls. Atomic-scale inhomogeneities near the defects can result in large-scale changes (involving hundreds or thousands of interatomic distances) of the magnetization distribution. Thus, to describe dynamics of real magnets one has to solve a typical multiscale problem, where the "defect" regions should be described at an atomic scale whereas for the rest of the sample a continuum medium approximation (micromagnetic theory) may be applied. We have developed an approach to these problems which is based on the nonequilibrium statistical operator formalism.

Quantum dynamics of spin systems in a thermal bath.

Dynamics of quantum systems interacting with the environment is currently a subject of great interest because of its fundamental importance for providing a better understanding of interpreting quantum mechanics as well as for applications in quantum computers. In particular, decoherence by the environment is the main limiting factor for the physical realization of qubits (quantum bits) in quantum computers. A spin thermal bath, such as a nuclear spin system, is probably the most important case since it turns out to be essential down to very low temperatures. We investigate the interaction of few-spin qubits with a spin thermal bath by both computer simulations and study simpler models. Peculiarities of spin dynamics of magnetic molecules which might be interesting as possible physical realizations of the qubits are also considered.

Fermi surface of fcc Co for a ferromagnetic configuration (blue and yellow sheets) and for a non-collinear spin-spiral configuration (translucent sheet).

Atmospheric physics

The image to the right shows a snapshot of a simulation of how plasma turbulence can develop in the earth's ionosphere. This electrostatic, one-dimensional Vlasov simulation of Bernstein-Green-Kruskal (BGK) waves is an example product of numerical tools that are especially designed for calculations of complex dynamical structures in planetary atmospheres.

Click on image for entire simulation
(1 Mb MPEG)

Astronomy

Two of the largest storm systems on Jupiter are colliding (in June 2003), the famous Great Red Spot, and the smaller white oval. The latter is part of a belt of clouds that circles Jupiter faster than the Red Spot. Last time such a collision was observed the oval started being slowed by the Red Spot two weeks before, while the collision lasted for one month. After that the red colour of the Spot faded for several years. The picture was taken by Voyager 2, NASA, in 1979.
The Cat's Eye Planetary Nebulae, a dying star, three thousand light years away, imaged by the Hubble Space Telescope, NASA. This is a good example of the extremely complex structure showed by the outflows of gas and dust from stars in very late evolutionary stages.
The Aurorae of Jupiter, as portrayed by the Hupple Space Telescope on December 19, 2000.
The pair of galaxies NGC 3314. This pair seems to be lined up by chance -- the galaxies do not show any clear signs of gravitational interaction between them. The bright background galaxy offers a unique possibility to study the intricate structure of the dust clouds in the spiral arms of the foreground system. The estimated distance to the galaxies is 140 million light years. Hubble Space Telescope, NASA
The Cone Nebula (NGC 2264), a star-forming cloud of gas and dust in the Milky Way, about 2500 light-years away. Hubble Space Telescope, NASA.
A part of a large sunspot group near the centre of the solar disk center, as imaged by the New Swedish Solar Telescope at the Institute for Solar Physics, Royal Swedish Academy of Sciences, on July 15, 2003.