Beta-deformation
We will now consider the case of so-called beta-deformation.
Linearized beta-deformations transform in the following representation:
where the subindex 
 means zero internal commutator;
has 
.
The nonlinear solutions were studied in:
O.Aharony, B.Kol, and S.Yankielowicz,
On exactly marginal deformations of 
 SYM and type IIB supergravity
   on 
https://arxiv.org/abs/hep-th/0205090
It was shown that the renormalization of beta-deformation is again a beta-deformation, and the anomalous dimension is an expression cubic in the deformation parameter.
In our language this corresponds to the obstacle starting at .
One would thing that the relevant cohomology group is:
But this cohomology group is zero, because 
is finite-dimensional.
What actually happens is:
where 
 is some infinite-dimensional extension of 
.
We will now explain this extension.