Relating on-shell and off-shell formalism in perturbative quantum field theory

Christian Brouder, Michael Dütsch
October 16, 2007
In the on-shell formalism (mostly used in perturbative quantum field theory) the entries of the time ordered product T are on-shell fields (i.e. the basic fields satisfy the free field equations). With that, (multi)linearity of T is incompatible with the Action Ward identity. This can be circumvented by using the off-shell formalism in which the entries of T are off-shell fields. To relate on- and off-shell formalism correctly, a map sigma from on-shell fields to off-shell fields was introduced axiomatically by Duetsch and Fredenhagen. In that paper it was shown that, in the case of one real scalar field in $N=4$ dimensional Minkowski space, these axioms have a unique solution. However, this solution was given there only recursively. We solve this recurrence relation and give a fully explicit expression for sigma in the cases of the scalar, Dirac and gauge fields for arbitrary values of the dimension $N$.
open access link J.Math.Phys.49:052303,2008
@article{Brouder:2007db, author = "Brouder, Christian and Dutsch, Michael", title = "{Relating on-shell and off-shell formalism in perturbative quantum field theory}", journal = "J. Math. Phys.", volume = "49", year = "2008", pages = "052303", doi = "10.1063/1.2918137", eprint = "0710.3040", archivePrefix = "arXiv", primaryClass = "hep-th", SLACcitation = "%%CITATION = ARXIV:0710.3040;%%" }

Keywords: 
off shell formalism, perturbative AQFT