An introduction to real-time renormalization group

This article presents a tutorial introduction to a recently developed real-time renormalization group method. It describes nonequilibrium properties of discrete quantum systems coupled linearly to an environment. We illustrate the technique by a simple and exactly solvable model: A quantum dot consisting of a single non-degenerate level coupled to two reservoirs. The article is intended for advanced students. Besides elementary quantum mechanics and statistical mechanics, it requires only knowledge of second quantization and Wick's theorem.