TMD gluon distributions at small x in the CGC theory

In this paper, we review recent progress in the description of unpolarized transverse-momentum-dependent (TMD) gluon distributions at small x in the color glass condensate (CGC) effective theory. We discuss the origin of the nonuniversality of TMD gluon distributions in the TMD factorization framework and in the CGC theory and the equivalence of the two approaches in their overlapping domain of validity. We show some applications of this equivalence, including recent results on the behavior of TMD gluon distributions at small x, and on the study of gluon saturation. We discuss recent advances in the unification of the TMD evolution and the nonlinear small-x evolution of gluon distributions.