Skip to main content
3 of 4
added 112 characters in body

A Fractional Linear Transformation Class Property

Let $\mathcal{S}$ be the class of Fractional Linear Transformations (or FLT's) consisting of $f: [-1,0] \rightarrow [-1,0]$ such that $f(x) = \frac{ax+b}{cx+d}$ where $a,b,c,d \in R$, and $f'(x)>0$ for all $x \in [-1,0]$.

Notice that given a fixed number $c>0$ (and you may suppose that $c \neq 1$ if necessary), there is a unique FLT $F \in \mathcal{S}$ such that the following three conditions hold:

$F(-1)=-1$, $F(0)=0$, and $\dfrac{F'(0)}{F'(-1)}=c^2$

I would like to ask for as many examples as possible of other classes of maps $\mathcal{C}$ (that is other than the class of FLT's) such that:

  1. $F'(x)>0$ for $x \in [-1,0]$.

  2. The same property as above of there existing a unique element in the class $\mathcal{C}$ satisfying the three conditions above holds.

  3. Additionally, the class of maps $\mathcal{C}$ satisfies the property of being closed under (functional) composition of its members.

Thank you in advance to all those who respond,

E(up)lio M.