Instantons, or pseudoparticles, are solutions to the equations of motion
in classical field theories on a Euclidean spacetime. Instantons are
found everywhere in quantum theories as they have many applications in
quantum tunnelling. Diverse physical phenomena may be described through
quantum tunnelling, for example: the Josephson effect, the decay of
meta-stable nuclear states, band formation in tight binding models of
crystalline solids, the structure of the gauge theory vacuum,
confinement in 2+1 dimensions, and the decay of superheated or
supercooled phases. Drawing inspiration from Sidney Coleman's Erice
lectures, this volume provides an accessible, detailed introduction to
instanton methods, with many applications, making it a valuable resource
for graduate students in many areas of physics, from condensed matter,
particle and nuclear physics, to string theory. This title, first
published in 2017, has been reissued as an Open Access publication on
Cambridge Core.