The unit ball of quadratic forms on an octagonal sector

Manwook Han, Sun Kwang Kim, Gustavo A. Muñoz-Fernández +1

Let \[\mathfrak O=\{(x,y)\in[0,1]^2:x+y\le \sqrt2\} \] be the first-quadrant sector of a regular octagon. For quadratic forms \(P(x,y)=ax^2+bxy+cy^2\), we study the supremum norm o…