  Two related constructions are associated with screening operators in models
of two-dimensional conformal field theory. One is a local system constructed in
terms of the braided vector space X spanned by the screening species in a given
CFT model and the space of vertex operators Y and the other is the Nichols
algebra B(X) and the category of its Yetter--Drinfeld modules, which we propose
as an algebraic counterpart, in a "braided" version of the Kazhdan--Lusztig
duality, of the representation category of vertex-operator algebras realized in
logarithmic CFT models.
