arXiv subjects
Publications and source records attributed to Fritz Schweiger.
The first part deals with piecewise fractional linear maps with three branches. Given a map $T$ a map $S$ is called a related map if some branches of $T$ are replaced by a 'flipped' branch, namely a branch of $1-T$. The main question is if $T$ and $S$ have a common invariant measure. The short second part presents invariant measures of a new type.
Piecewise fractional linear maps wzth three or more branches have been studied in several papers. For many Moebius maps the shape of the density of their invariant measurs can be written down exactly. However, if just two branches are linear, no explicit form is known. In this paper a partial solution is offered.
Here we consider piecewise fractional linear maps with three branches. The paper presents a study of invariant measures with densities which can be written as infinite series. These series either have infinitely many poles or they sum up to a function with just one pole.
A Moebius system is an ergodic fibred system $(B,T)$ (see \citer5) defined on an interval $B=[a,b]$ with partition $(J_k),k\in I,#I\geq 2$ such that $Tx=\frac{c_k+d_kx}{a_k+b_kx}$, $x\in J_k$ and $T|_{J_k}$ is a bijective map from $J_k$ onto $B$. It is well known that for $#I=2$ the invariant density can be written in the form $h(x)=\int_{B^*}\frac{dy}{(1+xy)^2}$ where $B^*$ is a suitable interval. This result does not hold for $#I\geq 3$. However, in this paper for $#I=3$ two classes of interval maps are determined which allow the extension of the before mentioned result.