$$ex fin C_c^infty(bR^2) a sen{f}_{L^4}leq sqrt{2} sen{f}_{L^2}^{1/2} sen{p_1f}_{L^2}^{1/4} sen{p_2f}_{L^2}^{1/4}, eex$$ $$ex fin C_c^infty(bR^3) a sen{f}_{L^4}leq 2^{3/4} sen{f}_{L^2}^{1/4} sen{p_1f}_{L^2}^{1/4} sen{p_2f}_{L^2}^{1/4} sen{p_3f}_{L^2}^{1/4}. eex$$