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JOURNALS // Matematicheskii Sbornik // Archive

Mat. Sb. (N.S.), 1978 Volume 107(149), Number 2(10), Pages 199–217 (Mi sm2636)

This article is cited in 67 papers

Averaging differential operators with almost periodic, rapidly oscillating coefficients

S. M. Kozlov


Abstract: The Dirichlet problem
$$ D_ia_{ij}(x\varepsilon^{-1})D_ju_\varepsilon(x)=f(x)\quad\text{in}\quad\Omega,\qquad u_\varepsilon(x)|_{\partial\Omega}=f_1(x), $$
containing a small parameter $\varepsilon$ is considered, where the coefficients $a_{ij}(y)$ are almost periodic functions in the sense of Besicovitch. An averaged equation having constant coefficients is contracted, and the convergence of $u_\varepsilon(x)$ to the solution $u_0(x)$ of the averaged equation is proved. An estimate of the remainder $\sup_{x\in\Omega}|u_\varepsilon(x)-u_0(x)|\leqslant C\varepsilon$ is obtained under the condition that there are no anomalous commensurable frequences in the spectrum of the coefficients. For the problem in the whole space a complete asymptotic expansion in powers of $\varepsilon$ is constructed.
Bibliography: 12 titles.

UDC: 517.43

MSC: 35B15, 35B20, 35J25

Received: 08.12.1977


 English version:
Mathematics of the USSR-Sbornik, 1979, 35:4, 481–498

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© Steklov Math. Inst. of RAS, 2026