1-Point Functions for $\mathbb{Z}_2$-orbifolds of Lattice VOAs
Maneesha Ampagouni
TL;DR
This work computes the full set of 1-point functions for the $\mathbb{Z}_2$-orbifold $V=V_L^{\theta}\oplus (V_L^T)^{\theta}$ of a lattice VOA $V_L$ with rank $k=8l$ and even, positive-definite lattice $L$. By adapting Mason–Mertens techniques to a $\mathbb{Z}_2$-twisted Zhu theory, it derives reduction and recursion formulas that express twisted and untwisted correlators in terms of modular data and lower-weight objects, and then applies these to obtain explicit closed forms for all state-types (vacuum, Heisenberg, and lattice sectors) in the twisted space. The results establish that the 1-point functions are modular forms of weight equal to the state weight (up to a character), validating modular invariance for the orbifold theory and enriching the understanding of twisted sectors in lattice VOAs. The work thus provides concrete, computable formulas for orbifold 1-point functions and demonstrates their robust modular structure, with implications for orbifold VOA theory and moonshine phenomena.
Abstract
In this paper, we compute the 1-point correlation functions of all states for the $\mathbb{Z}_2$-orbifolds of lattice vertex operator algebras.
