quantum field theory

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The application of quantum mechanics to physical systems described by fields, such as electromagnetic fields, developed to make quantum mechanics both consistent with the theory of special relativity and more readily applicable to systems involving many particles or the creation and destruction of particles.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the branch of quantum physics that is concerned with the theory of fields; it was motivated by the question of how an atom radiates light as its electrons jump from excited states