We say a supersingular curve over a finite field $\mathbb F_q$ if supersingular if it's Frobenius eigenvalues (on $H^1(X,\mathbb Z_\ell)$) are of the form $q^{1/2}\alpha$ for $\alpha_i$ a root of unity.
As far as I know, the question: "For which pairs $(g,q)$ does there exist a supersingular curve of genus $g$ over $\mathbb F_q$" is open. Partial results that I know are:
- Over characteristic $2$, every genus occurs: van der Geer, van der Vlugt.
- Genus $4$ in arbitrary characteristic is known: https://arxiv.org/abs/1903.08095
- The Hermitian curve $y^q + y = x^{q+1}$ is supersingular for $q = p^n$. slide 20.
- The Supersingularity of Hurwitz Curves proves for a specific farmily of $(g,q)$.
- Theorem 1.1 here lists, for $4\leq g\leq 11$, some congruence conditions on $p$ for which there exist supersingular curves.
I am sure I have missed a few but I are there are any large families that I have missed? What is the state of the art today?