Grigori Kuzmin and Stellar Dynamics

Grigori Kuzmin was a very gifted dynamicist and one of the towering figures in the distinguished history of the Tartu Observatory. He obtained a number of important results in relative isolation which were later rediscovered in the West. This work laid the foundation for further advances in the theory of stellar systems in dynamical equilibrium, thereby substantially increasing our understanding of galaxy dynamics.Comment: 10 pages, 1 figure, to appear in Baltic Astronomy, proceedings of the conference "Expanding the Universe" held in Tartu, Estonia, 27-29 April, 201

Electric field induced by magnetic flux motion in superconductor containing fractal clusters of a normal phase

The influence of the fractal clusters of a normal phase, which act as pinning centers, on the dynamics of magnetic flux in percolative type-II superconductor is considered. The voltage-current characteristics of such a superconductor are obtained taking into account the effect of fractal properties of cluster boundaries on the magnetic flux trapping. It is revealed that the fractality reduces the electric field arising from magnetic flux motion and thereby raises the critical current of a superconductor.Comment: 8 pages with 4 figures, revtex, alternative e-mail of author is [email protected]

Fractal geometry of normal phase clusters and magnetic flux trapping in high-Tc superconductors

The effect of geometry and morphology of superconducting structure on magnetic flux trapping is considered. It is found that the clusters of normal phase, which act as pinning centers, have significant fractal properties. The fractal dimension of the boundary of these clusters is estimated using a simple area-perimeter relation. A superconductor is treated as a percolation system. It is revealed that the fractality intensifies the magnetic flux trapping and thereby enhances the critical current value.Comment: 5 pages with 1 table and 2 figures, revtex, published in Phys.Lett.A 267 (2000) 66 with more complicated figure