A drop of dye added to a glass of water undergoes ordinary diffusion. However, when placed on the surface of a foam, the dye spreads differently—diffusion becomes anomalous. An example of this is the pattern on the froth of a cup of cappuccino. Interestingly, recent research suggests that diffusion equations in a heterogeneous environment can also describe social phenomena, such as election results or the behavior of stock market traders. The study is published in the Chaos: An Interdisciplinary Journal of Nonlinear Science.
The movement of particles in complex media—such as porous materials, gels or foams—bears more resemblance to a random journey through an irregular maze than to a leisurely stroll through a homogeneous space. The presence of local “traps” alongside narrow passages or branches causes the transport of matter or energy to be significantly slowed down or accelerated. Such deviations from classical diffusion are referred to as anomalous diffusion. It is also observed in media with a nonuniform structure.
An international team of physicists from Poland, Croatia, Macedonia and Hungary has undertaken a mathematical description of diffusion in such systems; the Polish side was represented by scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow.
