Bruno Zumino, a physicist who proposed a theory called supersymmetry that promised to help tie together the fundamental laws of the universe but that has yet to be borne out in experiments, died June 21 at his home in Berkeley, Calif. He was 91.

His death was confirmed by the University of California, Berkeley, where he was an emeritus professor.

Dr. Zumino developed supersymmetry with Julius Wess, a colleague at the CERN particle physics laboratory in Switzerland. It predicted the discovery of elementary particles that have yet to be observed in particle collision experiments at the Large Hadron Collider at CERN.

Nonetheless, “supersymmetry is still an extremely attractive idea,” said Steven Weinberg, a professor of physics at the University of Texas.