  We describe a procedure to deform the dynamics of a two-dimensional conformal
net to possibly obtain a Haag-Kastler net on the de Sitter spacetime. The new
dynamics is given by adding a primary field smeared on the time-zero circle to
the Lorentz generators of the conformal net.
  As an example, we take an extension of the chiral U(1)-current net by a
charged field with conformal dimension d < 1/4. We show that the perturbing
operators are defined on a dense domain.
