Abstract (eng)
This thesis deals with holomorphic functions $\Os_{d}^{p} \to \Os_{d}$, where $\Os_{d}$ denotes the ring of convergent power series in $d$ variables. In the first two chapters the necessary concepts from functional analysis and topology are developed.
The representation of $\Os_{d}$ as union $\bigcup_{S \in \R_{+}^{d}} \ell^{\infty}(S)$ of weighted Banach spaces yields a natural inductive topology, where $\ell^{\infty}(S)$ is the Banach space of power series for which $\sup_{\alpha \in \N^{d}} \vert c_{\alpha} S^{\alpha} \vert $ is finite. It turns out that $\Os_{d}$ is a (DFS)-space, which seems to be the best setting for the usage of concepts of infinite-dimensional calculus, as different approaches coincide and smooth functions are always continuous, which is in general false. In chapter three we give an overview of two concepts of holomorphicity. Chapter four then specifically deals with $\Os_{d}$ and the holomorphic functions on it. We extend the result by Dineen and Boland, that holomorphic functions $\Os_{d} \to \C$ can be expanded into monomial series, to the vector-valued case $\Os_{d} \to \Os_{d}$ and establish some results on the space $(\mathcal{H}(\Os_{d}^{p}, \Os_{d}),\tauco)$. The last chapter treats a special class of holomorphic functions $\Os_{d}^{p} \to \Os_{d}$, whose Taylor coefficients have a similar structure as those of substitution maps\\ $\phi(x) \mapsto F(x,\phi(x))$. We start by studying such maps that ignore the constant term $\phi(0)$ -- which we call textile maps -- which behave similar to linear maps in normed spaces: they are continuous if and only if they preserve the boundedness of a "ball". The same condition also implies that maps of this class are entire functions. It is then shown that the space of these maps equipped with the compact-open topology is a (DFS)-space and the results established before are then generalized to broader classes. Finally we turn our attention to the differential equation $\delta_{t} u(x,t) = F(u(x,t))$, where the right side is a generalized textile map, and show that it is analytically solvable for analytical initial conditions. A consequence of this result is that $\delta_{t}u(x,t) = F(x,u(x,t))$ (where $F$ is a convergent power series) remains analytically solvable if the coefficients of the right side (considered as a holomorphic function $\Os_{d}^{p} \to \Os_{d}^{p}$) are continuously perturbated.
%Finally we turn our attention to the differential equation $\delta_{t} u(x,t) = F(u(x,t))$, where the right side is a generalized textile map, and show that it is analytically solvable for analytical initial conditions.
%This result can be interpreted in the way that $\delta_{t}u(x,t) = F(x,u(x,t))$ remains analytically solvable if the coefficients of the right side (considered as a holomorphic function $\Os_{d}^{p} \to \Os_{d}^{p}$) are continuously perturbated.