Vertex operatorsThe relation between integrated and unintegrated vertices is called “the descent”.It does not always work.

For example, the deformation of the BRST structure corresponding to linear dilaton which we introduced a few slides before does not correspond to any integrated vertex , because the corresponding deformation of the action is simply .

But the corresponding unintegrated vertex operator does exist:Conclusion: it is better to describe deformations using unintegrated vertex operators.