# Mathematicians Build 'Perfect' Terrorist Cell

Like something straight from a thriller or the TV show "24," mathematicians have figured out a model to describe the perfect terrorist cell.

Using a complicated graph technique called lattice theory, the researchers created a diagram of the best possible way terrorists should organize themselves in order to avoid crumbling when members are captured.

"A terrorist cell is like any company organizational chart, with the leader at the top all the way down to the foot soldiers," explained Jonathan Farley, a mathematician at Caltech, "so you might imagine that to disrupt a cell, that would involve removing certain important leaders to cut off communications."

The question of creating the most indestructible network becomes mathematical as long as you can stick to certain universal assumptions, said Farley, who hopes his theory might eventually be adopted by authorities in the fight against terrorism.

Farley isn't the only mathematician pondering all this. At a 2004 meeting, several researchers outlined ideas for how science might help in the fight against terrorism.

Farley has kept at it since then, and his approach, "Toward a Mathematical Theory of Counterterrorism: Building the Perfect Terrorist Cell," will be published in an upcoming Proteus Monograph Series book.

Which branch to trim?

To imagine the perfect terrorist cell as a mathematical formula, certain generalizations had to be made, Farley said.

"Our assumption is that terrorist attacks are carried out when the leaders come up with the plans and give orders," he told LiveScience, comparing the structure to a tree with many branches.

Consulting with terror specialists, the mathematicians also started with the supposition that the terrorist cell must be interconnected, that there's a limit to how many people one leader can supervise (three or four, at most) and that there are very few upper-echelon leaders.

With the assumptions in place, Farley and a team from McGill University in Montreal found the most robust tree structure.

The trick was determining which branches of the tree, and how many, need to be intercepted in order to disrupt the cell completely.

Mathematicians call this important group a "cut-set" — the minimum number of components in a graph that can be removed to cause a complete failure in the system.

"Basically, we figured out the collection of people who would need to be captured to achieve this," Farley said.

On purpose, or by accident

The tree structure benefit law enforcement and the military, Farley said, noting that a similar theory was used recently to shake down a drug and arms trafficking network operating in Jamaica.

"We can prove that this cell structure is the best one, so why not assume that your adversary is intelligent enough to figure it out," either purposefully, or even by accident, Farley said.

Testing needs to be done to find out if and where these "perfect cells" actually exist and how best to combat them, he said.

"I am open to someone telling me this is nonsense," said Farley, who hopes that the government will at least consider the theory in its policy decisions. "The point isn't just that these decisions have to be made. It's that you can make them with a rational system and that's better than no system at all."

For the time being, governments at all levels aren't generally open to accepting this kind of abstract thinking, Farley said.

"I do not get the impression that the U.S. government cares about mathematics," Farley said, "even though you can prove you can get better results with less money."