I1.4 If $\log _{2} a+\log _{2} b \geq \gamma$, determine the smallest positive value $\delta$ for $a+b$.
$$
\begin{array}{l}
\log _{2} a+\log _{2} b \geq 6 \\
a b \geq 2^{6}=64 \\
a+b=(\sqrt{a}-\sqrt{b})^{2}+2 \sqrt{a b} \geq 0+2 \times \sqrt{64}=16
\end{array}
$$

The smallest positive value of $\delta=16$