Waring's problem with almost proportional summands

Abstract: For $n \geq 3$, an asymptotic formula is derived for the number of representations of a sufficiently large natural number $N$ as a sum of $r = 2^n + 1$ summands, each of which is an $n$-th power of natural numbers $x_i$, $i = \overline{1, r}$, satisfying the conditions $$ |x_i^n-\mu_iN|\le H,\qquad H\ge N^{1-\theta(n,r)+\varepsilon},\qquad \theta(n,r)=\frac2{(r+1)(n^2-n)}, $$ where $\mu_1, \ldots, \mu_r$ are positive fixed numbers, and $\mu_1 + \ldots + \mu_n = 1$. This result strengthens the theorem of E.M.Wright.