Classical Solutions in Quantum Field Theory: Solitons and Instantons in High Energy PhysicsClassical solutions play an important role in quantum field theory, high energy physics and cosmology. Real time soliton solutions give rise to particles, such as magnetic monopoles, and extended structures, such as domain walls and cosmic strings, that have implications for early universe cosmology. Imaginary time Euclidean instantons are responsible for important nonperturbative effects, while Euclidean bounce solutions govern transitions between