2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/50196We review a recent progress in constructing low-energy effective action in N=4 super Yang-Mills theories. Using harmonic superspace approach we consider N=4 SYM in terms of unconstrained N=2 superfield and apply N=2 background field method to finding effective action for N=4 SU(n) SYM broken down to U(n)$^{n-1}$. General structure of leading low-energy corrections to effective action is discussed.9 pages, LaTeX, Talk given at the Conference "Quantization, Gauge Theory, and Strings" dedicated to the memory of Professor Efim Fradkin, June 5-10, 2000, Moscow, to be published in the ProceedingsHigh Energy Physics - Theorytext