# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"From tilings to coverings," by Knut W. Urban. *Nature,* 5 November 1998,pages 14-15.

"New Data Help Explain Crystals That Defy Nature," by Malcolm W. Browne.*New York Times,* 24 November 1998.

In recent years, physicists have discovered and developed the theory ofquasicrystals, a type of matter in which substances are not as disordered asglass or as periodic as a crystal. Although more than 100 quasicrystals have beenmade and identified in laboratories, they have not proved to be especiallyuseful. Nevertheless, they continue to inspire research about how and why theyform. Starting with tilings devised by the physicist Roger Penrose in 1974,mathematician Paul Steinhardt and a team of collaborators have developed newways to explain the structure of quasicrystals.

*--- Benjamin Stein*