2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/25462Lectures notes for 2004 Les Houches Summer School on "Nanoscopic Quantum Transport". These lectures contain an introduction to Keldysh formalism for interacting bosonic and fermionic systems, presented in the functional integral framework. Covered topics include: kinetic theory, relation to classical techniques (such as Martin--Siggia--Rose and Fokker--Planck), non--linear sigma model for disordered fermions, etc.70 pages, 7 figuresDisordered Systems and Neural NetworksMesoscale and Nanoscale Physicstext