  This paper is a continuations of the project initiated in the book string
topology for stacks. We construct string operations on the SO(2)-equivariant
homology of the (free) loop space $L(X)$ of an oriented differentiable stack
$X$ and show that $H^{SO(2)}_{*+dim(X) -2}(L(X))$ is a graded Lie algebra. In
the particular case where $X$ is a 2-dimensional orbifold we give a
Goldman-type description for the string bracket. To prove these results, we
develop a machinery of (weak) group actions on topological stacks which should
be of independent interest. We explicitly construct the quotient stack of a
group acting on a stack and show that it is a topological stack. Then use its
homotopy type to define equivariant (co)homology for stacks, transfer maps, and
so on.
