In 1986, while visiting an old MIT buddy at his home in Rio de Janeiro, coherent structures were serendipitiously created in the host's swimming pool - an immaculate white marble pool supplied with pure clean mountain water. The structures were observed as pairs of black disks surrounded by a bright halo on the bottom of the pool. They persisted for more than 15 minutes!
The effect was (in situ) deduced to be a Snell refraction from a pair of surface dimples of negative Gauss curvature (the dimples were caused by circulation of the water depressing the free surface of the water - air interface into point a few millimeters below ambient flat surface -- as if a pencil was pushed into a flat rubber sheet.). What was not observed until later is that these dimple pairs were connected by an unseen thread of circular shape that globally stabilized the two dimensional defects on the end of the string. If the string was severed, the Quark-like endcaps disappeared in a non-diffusive manner.
This effect has been called the Falaco effect, and the objects are called Falaco
The easily reproduced phenomena is a remarkable visual realization of the theory and importance of topological defects, and should occur in physical systems of all scales -- from the micro scales to the cosmological scales.
In the last few years there has been much speculation about the applicability of
topological string theory and topological defects to cosmology. The Falaco
solitons have obvious topological features of strings and d-branes, and yet
there does not exist a solution (that I know of) which describes this easily
It would be a good thesis problem to find such a solution. Not only would such
a solution describe a real physical phenomenon, but also it might give credence
to string theory, where convincing experimental verification of conjectures on a
cosmological scale are difficult.