Spotting evidence of directed percolation

November 17, 2009

A team of physicists has, for the first time, seen convincing experimental evidence for directed percolation, a phenomenon that turns up in computer models of the ways diseases spread through a population or how water soaks through loose soil. Their observation strengthens the case for directed percolation's relevance to real systems, and lends new vigor to long-standing theories about how it works. Their experiment is reported in Physical Review E and highlighted with a Viewpoint in the November 16 issue of Physics (

While directed percolation models are handy for describing things as diverse as sand flow and calcium dynamics in cells, no one had managed to find clear, reproducible evidence of the phenomenon in a controlled experiment.

Now a team of physicists from the University of Tokyo, in Japan, and CEA-Saclay, in France, have seen directed percolation in a layer of liquid crystals about a hundredth of a millimeter thick sandwiched between two glass plates connected to electrodes. When they increased the voltage above a threshold, they saw gray spots appearing. A spot could disappear spontaneously but also cause spots to pop up around it, similar to the way a virus can die in one individual after infecting people nearby. The team showed that the system exhibited many of the mathematical hallmarks of directed percolation--convincing evidence that the long-theorized phenomenon occurs in real systems.
Also in Physics:

Power laws in chess: Sergei Maslov writes a Viewpoint on a paper showing that the popularity of opening moves in chess, like that of websites or books, have a long tail.

Taking the wraps off cloaking: John Pendry writes a Trends article revealing the theoretical underpinnings of invisibility cloaks and discussing recent attempts to engineer invisibility.

American Physical Society

Related Computer Models Articles from Brightsurf:

Simpler models may be better for determining some climate risk
Typically, computer models of climate become more and more complex as researchers strive to capture more details of our Earth's system, but according to a team of Penn State researchers, to assess risks, less complex models, with their ability to better sample uncertainties, may be a better choice.

UCLA computer scientists set benchmarks to optimize quantum computer performance
Two UCLA computer scientists have shown that existing compilers, which tell quantum computers how to use their circuits to execute quantum programs, inhibit the computers' ability to achieve optimal performance.

Towards a new generation of vegetation models
Plants and vegetation play a critical role in supporting life on Earth, but there is still a lot of uncertainty in our understanding of how exactly they affect the global carbon cycle and ecosystem services.

Models explain changes in cooking meat
In new research published in EPJ Plus, a team of mathematicians show that by modelling meat as a fluid-saturated matrix of elastic proteins, which are deformed as the fluid moves, cooking behaviours can be simulated more precisely.

Computer-based weather forecast: New algorithm outperforms mainframe computer systems
The exponential growth in computer processing power seen over the past 60 years may soon come to a halt.

Seeing clearly: Revised computer code accurately models an instability in fusion plasmas
Subatomic particles zip around fusion machines known as tokamaks and sometimes merge, releasing large amounts of energy.

Methods and models
It's a well-known fact that the ocean is one of the biggest absorbers of the carbon dioxide emitted by way of human activity.

Putting vision models to the test
MIT neuroscientists have performed the most rigorous testing yet of computational models that mimic the brain's visual cortex.

3D models reveal why bigger bumblebees see better
By generating 3D images of bumblebees' compound eyes, researchers at Lund University in Sweden have discovered how bumblebees differ in their vision.

Models of life
Friedrich Simmel und Aurore Dupin, researchers at the Technical University of Munich (TUM), have for the first time created artificial cell assemblies that can communicate with each other.

Read More: Computer Models News and Computer Models Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to