News of the week

Week 49/2007: Where does mass go?

Urban residents facing urban problems

Professor Alexey Alexeevih Lushnikov has his office on the top floor of the Department of Physical Sciences in Kumpula. And in his own field, theoretical aerosol physics, he has also reached the top. He has received the most prestigious recognition in his field: the Fuchs Memorial Award and the Junge Award, the latter this year.

Lushnikov’s main interest lies in the theoretical research of coagulation. In coagulation, certain particles, such as aerosols, move chaotically and become attached to one another when colliding, thus forming larger particles. Usually the growth begins with something known as a coagulation kernel, onto which other particles attach themselves.

Describing the movement of coagulating particles is not, however, always possible with “ordinary" Boltzmann kinetic equations when on the thermodynamic limit - that is, when a vast number of particles are moving in a large space. When applying normal kinetic equations, the total mass of the system is not conserved if the coagulation kernel grows very rapidly, although mass cannot disappear in such a simple system.

Lushnikov already detected some of the problems related to coagulation in the 1970s. Because normal kinetic equations cannot be applied to the giant particles evolving in the system, new kinds of equations are required. However, another scientist, A.H. Marcus, had already managed to formulate a new scheme for the situation. Eventually it was Lushnikov who developed an exact solution for the movement in a coagulating system.

“My work is applicable  almost everywhere,” says Lushnikov. “In different areas, difference scales and different dimensions; for example, in planetary systems, and even for congested traffic.”

For the time being, Lushnikov’s work at the University of Helsinki is all but complete and with some sadness, he is returning to Moscow at the beginning of 2008.

“I have many friends and an excellent workplace in Helsinki. But I am optimistic that I can continue my research in Russia.”

Text: Kerttu Aitola
Photo: Veikko Somerpuro
www.helsinki.fi/digitalcommunications

Translation: Valtasana Oy