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JOURNALS // Matematicheskii Sbornik // Archive

Mat. Sb. (N.S.), 1973 Volume 92(134), Number 3(11), Pages 461–471 (Mi sm3417)

This article is cited in 1 paper

On the uniqueness of an expansion in generalized eigenfunctions of a differential operator

V. A. Tkachenko


Abstract: The space $\mathscr E_\rho$ of the entire functions of order $\rho$ ($1<\rho<\infty$) with the usual topology and the operator $\mathscr L$, induced by a differential operation $l[y]=y^n+p_{n-2}(z)y^{n-2}+\dots+p_0(z)y$, $n>1$, and “boundary” conditions $F_i[y]=0$ ($i=1,\dots,n$), where the $F_i$ are linear functionals on $\mathscr E_\rho$. Conditions are indicated under which the formal expansion $f\sim-\Sigma_\lambda\operatorname{Res}(\mathscr L-\lambda E)^{-1}f$ uniquely determines an element $f\in\mathscr E_\rho$. As a corollary it is established that if $\Delta(\lambda)=\Sigma c_k\lambda^k\in\mathscr E_\mu$, $\mu>1$, has an infinite number of zeros and $f(z)\in\mathscr E_\rho$, $\rho<\mu(\mu-1)$, then $f(z)\equiv0$ whenever
$$ \sum^\infty_{k=1}\frac{c_k(\lambda^{k-1}f(0)+\dots+f^{(k-1)}(0))}{\Delta(\lambda)} $$
is an entire function.
Bibliography: 10 titles.

UDC: 517.535.4

MSC: 35B25

Received: 27.03.1973


 English version:
Mathematics of the USSR-Sbornik, 1973, 21:3, 455–466

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