Can we classify infinitesimal deformations of ? In other words:

• What can we say about vertex operators in this backgrounds?

In my paper “Symmetries of massless vertex operators” I have shown that the vertex operators with large enough angular momentum have the following nice property:

There is a gauge in which vertex operators transform covariantly with respect to the superconformal transformations:

    (2)

Generally speaking the covariance holds only up to BRST transformation:

for some “gauge parameter” of the ghost number 1