Fourvolutions and automorphism groups of orbifold lattice vertex operator algebras

Hsian-Yang Chen, Ching Hung Lam

Let $L$ be an even positive definite lattice with no roots, i.e., $L(2)=\{x\in L\mid (x|x)=2\}=\varnothing$. Let $g\in O(L)$ be an isometry of order $4$ such that $g^2=-1$ on $L$. In…