Ultraviolet divergence

In physics, an ultraviolet divergence is a situation in which an integral, for example a Feynman diagram, diverges because of contributions of objects with very high energy (approaching infinity), or, equivalently, because of physical phenomena at very short distances. An infinite answer to a question that should have a finite answer is a potential problem. The ultraviolet (UV) divergences are often unphysical effects that can be removed by regularization and renormalization. If they cannot be removed, they imply that the theory is not perturbatively well-defined at very short distances.