On the sign patterns of entrywise positivity preservers in fixed dimension

Apoorva Khare, Terence Tao

Given $I\subset \mathbb{C}$ and an integer $N>0$, a function $f:I\to \mathbb{C}$ is entrywise positivity preserving on positive semidefinite (p.s.d.) matrices $A=(a_{jk})\in I^{N\tim…