fermonlijn

Fermonlijn is a term encountered in Dutch-language discussions of particle physics to refer to a line in Feynman diagrams that represents the propagation of a fermion between interaction vertices. The standard Dutch spelling is fermionlijn; 'fermonlijn' is a less common variant found in some sources.

In Feynman diagrams, fermions such as electrons, quarks, or neutrinos are drawn as solid lines with arrows indicating the direction of fermion number flow. A fermion line may extend across multiple vertices, and its ends correspond to external fermions or antifermions.

Mathematically, a fermion line corresponds to a fermion propagator, typically denoted S_F(p) = (p-slash - m + iε)^{-1} in momentum space, or S_F(x-y) in position space. The arrow on the line indicates whether the line represents a particle moving forward in time (fermion) or an antiparticle if time reversed, depending on the convention.

Use and context: The term is common in Dutch pedagogy and literature discussing quantum field theory and high-energy physics. It is not a separate physical object, but a notational element in diagrammatic perturbation theory. See also: Feynman diagram, fermion propagator, quantum electrodynamics, quantum chromodynamics.