1

We define the polar dual of a polytope $P$ as the set $$\{x\in \mathbb{R}^n: x \cdot a\geq -1 \text{ for all } a\in P\}$$ Why do we require $-1$ instead of $-2$ or any other constant?

flag
3 
 Any other negative constant works. Other formulas have a normalizing constant that will change if you use something other than $-1$. The value $-1$ is used because it is the "simplest" negative number and for that choice, the dual of a unit round ball (admittedly, not a polytope) is a unit round ball. – Deane Yang Aug 30 at 18:06

closed as off topic by Ryan Budney, Jon Bannon, Will Sawin, Noah Stein, Benoît Kloeckner Aug 31 at 8:43

1 Answer

4

It is just a normalization. If you were to pick any other constant (say, $-c$, where $c$ is positive), then it would only scale the set by a factor of $1/c$.

link|flag

Not the answer you're looking for? Browse other questions tagged or ask your own question.