David J. Thouless, who shared the 2016 Nobel Prize in Physics for discoveries that used mathematics to explain strange states of matter like superconductivity and superfluidity, died on April 6 in Cambridge, England. He was 84.

The University of Cambridge announced his death but did not provide a cause. Born in Scotland to English parents, Dr. Thouless had taught at Cambridge but received his Nobel while affiliated with the University of Washington.

Dr. Thouless’s research dealt with condensed-matter physics, and specifically with what happens when matter changes phases — as, for example, when ice melts and becomes a liquid or water boils and becomes steam.

Though phase transitions seem deceptively simple, the mathematics turn out to be exceedingly complex, and important — particularly when one looks at such a transition at the microscopic level using quantum mechanics.