Physicists find doubly transient chaos can emerge due to dissipation

 

phys.org

A team of researchers, one from the U.S. and the others from Hungary, has found that a condition they've dubbed doubly transient chaos can emerge from a system due to dissipation. In their paper they've had published in the journal Physical Review Letters, the team describes how their experiments with a triple-magnet pendulum showed that even systems that come to stop eventually can have chaos attributes.

At first blush, most people recognize chaos when they see it—a crowd of people, each behaving unpredictably, for example. In physics, chaos can be seen with examples such as the constantly changing images that result from fractal geometry. One property that all chaotic systems have in common is that changes continue occurring (due either to an external force or lack of one such as gravity or friction), aka, transient chaos, as long as the system is in existence—otherwise, the system would dissipate to a non-changing state. But, is that system that results chaotic as well? The researchers in this new effort say yes, but not in the same way as other chaotic systems. For that reason, they have called it doubly transient chaos.

Chaos can exist in even the simplest of systems, such as a pendulum, for example. If it's started and left to swing till it stops, it will follow a routine that can be accurately described mathematically—but not if it is disturbed periodically by an external energy source—say a person reaching over and pushing it a little bit to keep it going. If that extra push can't be described in an orderly way, then the motion and duration of the pendulum's swing can be described as chaotic. The researchers used just such an example to prove their idea about transient chaos. They used a pendulum with three magnets attached to a triangle—suggesting three final states for the pendulum when it finally stops moving. In such a setup, the pendulum was subject to magnetic forces, gravity, and air drag.

In studying the ways in which the pendulum swung and eventually stopped, the researchers found that it conformed to doubly transient chaos—one of whose hallmarks is that parameters describing its rate of change to a final state are not constant as they are with transient chaos, but are instead exponential.

The researchers believe that doubly transient chaos may be at play in many other systems (chemical reactions, binary star behavior, etc.) and because of that are likely far less predictable than has been previously thought. 

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