Definition:Negative of Cut
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Definition
Let $\alpha$ be a cut.
Let $0^*$ be the rational cut associated with the (rational) number $0$:
- $0^* = \set {r \in \Q: r < 0}$
Let $\beta$ be the unique cut such that:
- $\alpha + \beta = 0^*$
where $+$ denotes the operation of addition of cuts.
Then $\beta$ is referred to as the negative of $\alpha$.
It is usually denoted $-\alpha$.
Also see
- Existence of Unique Inverse Element for Addition of Cuts, which proves both existence and uniqueness of $-\alpha$ for a given $\alpha$
Sources
- 1964: Walter Rudin: Principles of Mathematical Analysis (2nd ed.) ... (previous) ... (next): Chapter $1$: The Real and Complex Number Systems: Dedekind Cuts: $1.17$. Definition