\(\DeclarePairedDelimiterX{\Set}[2]{\{}{\}}{#1 \nonscript\;\delimsize\vert\nonscript\; #2}\) \( \DeclarePairedDelimiter{\set}{\{}{\}}\) \( \DeclarePairedDelimiter{\parens}{\left(}{\right)}\) \(\DeclarePairedDelimiterX{\innerproduct}[1]{\langle}{\rangle}{#1}\) \(\newcommand{\ip}[1]{\innerproduct{#1}}\) \(\newcommand{\bmat}[1]{\left[\hspace{2.0pt}\begin{matrix}#1\end{matrix}\hspace{2.0pt}\right]}\) \(\newcommand{\barray}[1]{\left[\hspace{2.0pt}\begin{matrix}#1\end{matrix}\hspace{2.0pt}\right]}\) \(\newcommand{\mat}[1]{\begin{matrix}#1\end{matrix}}\) \(\newcommand{\pmat}[1]{\begin{pmatrix}#1\end{pmatrix}}\) \(\newcommand{\mathword}[1]{\mathop{\textup{#1}}}\)
Needs:
Geometry
Integer Arithmetic
Needed by:
Chordal Graphs
Real Line
Links:
Sheet PDF
Graph PDF

Integral Line

Why

We are constantly thinking of the integers as the endpoints of equal length segments of a line.

Discussion

We commonly associate elements of the integers with the endpoints of equal-length segments of a real line. Take segment $S_0$ of $L$ with endpoints $p$ and $q$. Associate the point $p$ with $0$. Associate the point $q$ with $1$. Take a segment $S_1$ of equal length, non-overlapping with $S_0$, who shares the endpoint $q$. Associate the second endpoint of this segment $2$. Continue with the rest. We call the line so formed the integral line of unit $S_0$.

Integral Distance

Let $f: \Z \to \Z $ be defined by $f(a, b) = a - b$ if $a > b$ and $f(a, b) = b - a$ if $b > a$. Notice that $f$ is symmetric: $f(a,b) = f(b, a)$. The (geometric) interpretation of $f$ is the distance between the points associated with the two integers $a, b \in \Z $ in some integral line. We call $f$ the integral distance. Notice that $f(a, b) > 0$ for all $a, b \in \Z $.

Notation

We denote the distance between $a, b \in \Z $ by $\abs{a - b}$.

Copyright © 2023 The Bourbaki Authors — All rights reserved — Version 13a6779cc About Show the old page view