Llega el primer preprint de la serie Hecho en México 2.0.
Quantum/thermal fluctuations in quantum mechanics and field theories from a new version of semiclassical theory
We develop a new semiclassical approach, which starts with the density matrix given by the Euclidean time path integral with fixed endpoints, and proceed by identifying classical (minimal Euclidean action) path, we name “flucton”, which passes through this point. Fluctuations around flucton path are included, by standard Feynman diagrammatic series, previously developed for instantons. Two classic examples – quartic double-well and sine-Gordon potentials – are discussed in detail. Unlike other semiclassical methods, like WKB, we do not use Schr\”odinger equation, and all the steps generalize to multi-dimensional or quantum fields cases straightforwardly.