An explicit upper bound for the Helfgott delta in SL(2,p)

Button, Jack ; Roney-Dougal, Colva M (2014-09-23)


Helfgott proved that there exists a δ > 0 such that if S is a symmetric generating subset of SL(2, p)containing 1 then either S^3=SL(2, p)or |S^3| ≥|S|^1+ δ. It is known that δ ≥ 1/3024. Here we show that δ ≤ (log_2 (7) −1)/6 ≈ 0.3012and we present evidence suggesting that this might be the true value of δ.