摘要

Let G be a subgroup of Z(q)(*). and #G = t, set S(G) = max(a is an element of Zq*)(vertical bar)Sigma(x is an element of G) e(q)(ax)vertical bar. and T-k(G):= #1(x(1), x(2), ..., x(2k)): x(1) + ... + x(k) = x(k+1) + ... + x(2k) (mod q) x(1) is an element of G). As q = p(2), we obtain the general cases of T-k(G), then one can easily obtain the nontrivial bound of S(G) as p(2/3+epsilon) <t <= p, which improves t > p(7/10) from Malykhin (2005) [12]. On the other hand, it is known J. Bourgain obtain the nontrivial bound for t > p(epsilon) with arbitrary epsilon > 0 by the sum-product method, however his bounds not be explicit. We also give some connections between T-k(G) and Erdos-Szemeredi Conjecture.

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