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On the DSM version of Newton's method
A. G. Ramm Mathematics Department, Kansas State University, Manhattan, KS, USA
Аннотация:
The DSM (dynamical systems method) version of the Newton's method is for solving operator equation
$F(u)=f$ in Banach spaces is discussed. If
$F$ is a global homeomorphism of a Banach space
$X$ onto
$X$, that is continuously Fréchet differentiable, and the DSM version of the Newton's method is
$\dot u=-[F'(u)]^{-1}(F(u)-f)$,
$u(0)=u_0$, then it is proved that
$u(t)$ exists for all
$t\ge0$ and is unique, that there exists
$u(\infty):=\lim_{t\to\infty}u(t)$, and that
$F(u(\infty))=f$. These results are obtained for an arbitrary initial approximation
$u_0$. This means that convergence of the DSM version of the Newton's method is global. The proof is simple, short, and is based on a new idea. If
$F$ is not a global homeomorphism, then a similar result is obtained for
$u_0$ sufficiently close to
$y$, where
$F(y)=f$ and
$F$ is a local homeomorphism of a neighborhood of
$y$ onto a neighborhood of
$f$. These neighborhoods are specified.
Ключевые слова и фразы:
nonlinear equations, homeomorphism, surjectivity, dynamical systems method (DSM).
MSC: 58C15,
47J05,
65J08 Поступила в редакцию: 22.01.2011
Язык публикации: английский