纸上谈兵的准晶体对于地面上铺的瓷砖,大家一定不陌生。最简单的大概要算在厕所里常见的用单一颜色的正方形马赛克所铺成的地面。复杂一点的,则可以用多种颜色和多种形状(比如正三角形加正六边形)来铺设。更复杂些的,还可以用瓷砖排成图案。不管是简单的还是复杂的,它们通常都具有一些共性。其一是全面覆盖,即不会留下空缺的面积。其二是具有一定的秩序,或者说遵从某种规则。其三是周期性,也就是重复性。比如,把由单一颜色的正方形马赛克所铺成的地面想象成能 Quasi crystal on paper Speaking of ceramic tiles on the ground, we must not be new. The simplest thing to do is to count the floors that are paved with a single-colored square mosaic that is common in toilets. Complicated, you can use a variety of colors and a variety of shapes (such as regular triangles and regular hexagons) to laying. More complex, you can also use ceramic tile lined. Whether simple or complex, they usually have some commonality. One is full coverage, that is, the area that will not leave a vacancy. The second is to have a certain order, or to comply with certain rules. The third is cyclical, that is, repetitive. For example, imagine the ground paved with a single-color square mosaic