\( \text{The set of } (x,y,z) \in \mathbb{R}^3 \text{ for which all eigenvalues of }
\begin{bmatrix}
1 & x & y \\
x & 1 & z \\
y & z & 1
\end{bmatrix}
\text{ are nonnegative.} \)
\(\text{Click on “Render" to generate and show the elliptope.}\)
\(\text{Click on “Toggle Stereo" to show a splay-eyed stereoscopic view}\).