 Working with Howard Georgi and Steven Weinberg, Quinn showed how the three types of particle interactions (strong, electromagnetic, and weak), which look very different as we see their impact in the world around us, become very similar in extremely high-energy processes and so might be three aspects of a single unified force.With Roberto Peccei, she originated [[Peccei–Quinn theory], which suggested a possible near-symmetry of the universe (now known as [[Peccei–Quinn symmetry]]) to explain how strong interactions can maintain [[CP-symmetry]] (the symmetry between matter and antimatter) when weak interactions do not.One consequence of this theory is a particle known as the [[axion]] which has yet to be observed but is one candidate for the [[dark matter]] that pervades the universe.