context: University of Chicago scholars have played a major role in the development of various academic disciplines, including: the Chicago school of economics, the Chicago school of sociology, the law and economics movement in legal analysis, the Chicago school of literary criticism, the Chicago school of religion, and the behavioralism school of political science. Chicago's physics department helped develop the world's first man-made, self-sustaining nuclear reaction beneath the university's Stagg Field. Chicago's research pursuits have been aided by unique affiliations with world-renowned institutions like the nearby Fermilab and Argonne National Laboratory, as well as the Marine Biological Laboratory. The university is also home to the University of Chicago Press, the largest university press in the United States. With an estimated completion date of 2020, the Barack Obama Presidential Center will be housed at the university and include both the Obama presidential library and offices of the Obama Foundation.
question: Under which field did the world's first synthetically produced nuclear reaction occur?