Physics tip sheet #42( 1) Time Reversed Signals for Future Ce...)

In recent years, researchers have found that they can improve acoustic signal transmission in complex environments with a technique known as time reversal. In effect, they broadcast a signal to determine how it propagates through an arrangement of obstructions, and then send a reversed version of the signal back from the detectors to the original source. Now researchers at the Laboratoire Ondes et Acoustique in Paris have managed to apply the same technique to electromagnetic signals at 2.45 GHz, a frequency close to the operating range of cell phones. The experiment heralds the possibility of improving cell phone communications in cities and other environments where obstructions, such as skyscrapers, may eventually aid cellular performance rather than hindering it.

2) Exploiting Noise to Increase Profits
A. Traulsen et al.
Physical Review Letters (to appear)

The interactions between populations with different ambitions (shoppers and sellers, attackers and defenders, men and women) can lead to intricate and complicated dynamics as competitors struggle to adapt and gain an advantage. Researchers at the Christian-Albrechts University in Germany now find that it's not only beneficial for competitors to adapt, but it can also be helpful for them to adjust the rate at which they adapt. The researchers studied competition in numerical models that included random fluctuations, i.e. statistical noise. They found that flexible competitors who adjust their adaptation rate could improve their prosperity in noisy systems. The researchers suggest that their model may have important economic implicatio
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Contact: James Riordon
riordon@aps.org
301-209-3238
American Physical Society
24-May-2004