## Publicacions Matemàtiques

### Stabilization in $H^\infty_{\mathbb{R}}(\mathbb{D})$

Brett D. Wick

#### Abstract

It is shown that for $H^\infty_\mathbb{R}(\mathbb{D})$ functions $f_1$ and $f_2$ with

$\inf_{z\in\mathbb{D}}(\vert f_1(z)\vert+\vert f_2(z)\vert)\geq\delta>0$

and $f_1$ being positive on the real zeros of $f_2$, then there exists $H^\infty_\mathbb{R}(\mathbb{D})$ functions $g_2$ and $g_1$, $g_1^{-1}$ with norm controlled by a constant depending only on $\delta$ and

$g_1f_1+g_2f_2=1\quad\forall\; z\in\mathbb{D}$.

These results are connected to the computation of the stable rank of the algebra $H^\infty_\mathbb{R}(\mathbb{D})$ and to results in Control Theory.

#### Article information

Source
Publ. Mat., Volume 54, Number 1 (2010), 25-52.

Dates
First available in Project Euclid: 8 January 2010

https://projecteuclid.org/euclid.pm/1262962131

Mathematical Reviews number (MathSciNet)
MR2603587

Zentralblatt MATH identifier
1193.46033

#### Citation

Wick, Brett D. Stabilization in $H^\infty_{\mathbb{R}}(\mathbb{D})$. Publ. Mat. 54 (2010), no. 1, 25--52. https://projecteuclid.org/euclid.pm/1262962131

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• See also: Brett D. Wick. Corrigendum: "Stabilization in \boldmath$H^\infty_{\mathbb{R}}(\mathbb{D})$". Publ. Mat. Volume 55, Number 1 (2011), 251-260.