An important problem in statistical mechanics has also proved vulnerable to Ramanujan’s mathematics—a theoretical model that explains, for example, how liquid helium disperses through a crystal lattice of carbon. As it happens, the sites helium molecules may occupy in a sheet of graphite, say, can never lie adjacent to one another. Since each potential site is surrounded by six neighbors in a hexagonal array, once it is filled, the six around it define an unbreachable hexagonal wall. Reviewing in 1987 the work for which he received the prestigious Boltzmann Medal seven years earlier, R. J.
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