Editing String field theory (section)

===Other formulations of covariant open superstring field theory===
A formulation of superstring field theory using the non-minimal pure-spinor variables was introduced by Berkovits.<ref>{{cite journal | last=Berkovits | first=Nathan | title=Pure spinor formalism as an N= 2 topological string | journal=Journal of High Energy Physics | volume=2005 | issue=10 | date=2005-10-27 | issn=1029-8479 | doi=10.1088/1126-6708/2005/10/089 | pages=089|doi-access=free|arxiv=hep-th/0509120| bibcode=2005JHEP...10..089B }}</ref> The action is cubic and includes a midpoint insertion whose kernel is trivial. As always within the pure-spinor formulation, the Ramond sector can be easily treated. However, it is not known how to incorporate the GSO- sectors into the formalism.

In an attempt to resolve the allegedly problematic midpoint insertion of the modified cubic theory, Berkovits and Siegel proposed a superstring field theory based on a non-minimal extension of the RNS string,<ref>{{cite journal | last1=Berkovits | first1=Nathan | last2=Siegel | first2=Warren | title=Regularizing cubic open Neveu-Schwarz string field theory | journal=Journal of High Energy Physics | volume=2009 | issue=11 | date=2009-11-05 | issn=1029-8479 | doi=10.1088/1126-6708/2009/11/021 | pages=021|arxiv=0901.3386| bibcode=2009JHEP...11..021B | s2cid=16824165 }}</ref> which uses a midpoint insertion with no kernel. It is not clear if such insertions are in any way better than midpoint insertions with non-trivial kernels.