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Short Communications
On the asymptotic behaviour of the first eigenvalue of a second-order differential operator with small parameter by the higher derivatives
A. D. Wentzel' Moscow
Abstract:
An application of results concerning Markow processes to investigation of eigenvalues of linear operators is given.
Let $L^h=\sum b^i(x)\partial/\partial x^i+(h/2)\sum a^{ij}(x)\partial^2/\partial x^i\partial x^j$, for each
$h>0$, be an elliptic operator in a bounded domain
$D\subset R^r$;
$\lambda_1(h)$ be the first (i.e., minimal) eigenvalue of the operator
$-L^h$ with zero boundary condition on
$\partial D$. It was shown in [2], [3] that, if in
$D$ there exists a finite number of compacts containing stable
$\omega$-limiting sets of the dynamical system
$\dot x_t=b(x_t)$, then
$\lambda_1(h)$ tends to 0 with an exponential rate when
$h\downarrow0$. In this paper, we show that, if all solutions of
$\dot x_t=b(x_t)$ sooner or later leave
$D\bigcup\partial D$, then
$\lambda_1(h)=c_1h^{-1}+o(h^{-1})$; a formula for the constant
$c_1$ is given. The proof, as well as in [2], uses the diffusion process
$(x_t^h,\mathbf P_x^h)$ corresponding to
$L^h$ and the exit time
$\tau^h$ for
$D$ and the theorems of [1] concerning probabilities of certain nearly improbable events.
Received: 30.07.1974