How Quantum Field Theory?
Students are often confused over the difference (and whether or not there is a difference) between relativistic quantum mechanics (RQM) and quantum field theory (QFT.) The following discussion, summarized in Unifying Chart 1, should help to distinguish them. In using Unifying Chart 1, the reader should be aware that, depending on context, the term “quantum mechanics” can mean i) only non-relativistic (“ordinary”) quantum mechanics (NRQM), or ii) the entire realm of quantum theories including NRQM, relativistic quantum mechanics (RQM), and QFT. In the chart, we employ the second of these. Classical mechanics has both a non-relativistic and a relativistic side, and each contains a theory of particles (localized entities, typically pointlike objects) and a theory of fields (entities extended over space and time). All of these are represented in the first row of Unifying Chart 1. Properties (dynamic variables) of entities in classical particle theories are “total” values, such as object ma
