Given a family $$\varphi = (\varphi_1, \ldots, \varphi_d)\in \mathbb{Z}[T]^d$$ of d distinct nonconstant polynomials, a positive integer $$k\le d$$ and a real positive parameter $$\rho$$ , we consider the mean value $$M_{k, \rho} (\varphi, N) = \int_{{\rm x} \in [0,1]^k} \sup_{{\rm y} \in [0,1]^{d-k}} | S_{\varphi}({\rm x}, {\rm y}; N) |^\rho \,d{\rm x} $$ of exponential sums $$S_{\varphi}({\rm x}, {\rm y}; N) = \sum_{n=1}^{N} \exp\biggl(2 \pi i\biggl(\sum_{j=1}^k x_j \varphi_j(n)+ \sum_{j=1}^{d-k}y_j\varphi_{k+j}(n)\biggr)\biggr), $$ where $${\rm x} = (x_1, \ldots, x_k)$$ and $${\rm y} =(y_1, \ldots, y_{d-k})$$ . The case of polynomials $$\varphi_i(T) = T^i, i =1, \ldots, d$$ and $$k=d$$ corresponds to the classical Vinaogradov mean value theorem. Here motivated by recent works of Wooley [14] and the authors [9] on bounds on $${\rm sup}_{{\rm y} \in [0,1]^{d-k}} | S_{\varphi}({\rm x}, {\rm y}; N) |$$ for almost all $${\rm x} \in [0,1]^k$$ , we obtain nontrivial bounds on $$M_{k, \rho} (\varphi, N)$$ .
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