Thank you very much for making this book available, it's very interesting and very well written.
I spotted a mistake (I think?) in the explanation in the relating orderings chapter.
I think for the pushforward orderings we need f to be bijective, but the reason is simply that we need to map each input to the output space, otherwise orderings won't be defined in Y.
So this is correct I think: "If f is not also surjective, and hence bijective, then we cannot pushforward orderings on the input space to orderings on the output space." But the explanation is wrong (see snippet):
|
orderings on the output space. The problem is that if any pair |
|
of output elements are associated with multiple input elements, |
|
\begin{align*} |
|
y_{1} &= f(x_1) = f(x_1') |
|
\\ |
|
y_{2} &= f(x_2) = f(x_2'), |
|
\end{align*} |
|
then we can have conflicting input orderings, |
|
\begin{align*} |
|
x_1 &< x_2 |
|
\\ |
|
x_2' &< x_1', |
|
\end{align*} |
|
that cannot be combined into a consistent output ordering. |
Does it make sense? Thanks!
Francesco
Thank you very much for making this book available, it's very interesting and very well written.
I spotted a mistake (I think?) in the explanation in the relating orderings chapter.
I think for the pushforward orderings we need f to be bijective, but the reason is simply that we need to map each input to the output space, otherwise orderings won't be defined in Y.
So this is correct I think: "If f is not also surjective, and hence bijective, then we cannot pushforward orderings on the input space to orderings on the output space." But the explanation is wrong (see snippet):
quarto_chapters/2_mathematical_spaces/spaces.qmd
Lines 2007 to 2020 in 8fd23d2
Does it make sense? Thanks!
Francesco