Structure of light front vacuum sector diagrams

Understand

We study the structure of scalar field light front quantization vacuum graphs.

• In instant time quantization both non-vacuum and vacuum graphs can equivalently be described by either the off-shell four-dimensional Feynman diagram approach or the on-shell three-dimensional Fock space approach, with this being the case since the relevant Feynman diagrams are given entirely by pole terms.
• This is also the case for light front quantization non-vacuum graphs.
• However this is the not the case for light front vacuum sector diagrams, since then there are also circle at infinity contributions to Feynman diagrams.