The perturbative non-linear (NL) effects in the small-x evolution of the gluon densities depend crucially on the infrared (IR) regularization. The IR regulator, Rc, is determined by the scale of the non-perturbative fluctuations of QCD vacuum. From the instanton models and from the lattice Rc ∼ 0.3 fm. For perturbative gluons with the propagation length Rc = 0.26 fm the linear BFKL gives a good description of the proton structure function F2(x,Q2) in a wide range of x and Q2. The NL effects turn out to be rather weak and amount to the 10% correction to F2(x,Q2) for x ≲ 10−5. Much more pronounced NL effects were found in the non-linear model, described in the literature, with a very soft IR regularization corresponding to the IR cutoff at ≃Λ−1QCD The latter issue is also commented below.

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