Is PCP soundness error optimally 1/2?
In the full version of Delegating Computation: Interactive Proofs for Muggles on the bottom of page 18 it says that it is well known that interactive protocols with input size $n$, completeness $2/3$, and soundness $1/3$, are equivalent to interactive protocols with completeness $1-2^{-n}$ and soundness $2^{-n}$. Though soundness $1/3$ differs from $1/2$ mentioned in the question, a similar equivalence likely exists. Apparently the equivalence is proven somewhere in Goldreich's lengthy paper Modern cryptography, probabilistic proofs and pseudorandomness, volume 17 of Algorithms and Combinatorics.