Modular Zhu algebra theory and Virasoro vertex algebras
Abstract
We develop the representation theory of vertex algebras over arbitrary commutative rings as part of a relative theory, suitable for various applications such as the study of modular forms, modular tensor categories, and sheaves of coinvariants and conformal blocks. Towards this end, we construct Zhu algebras (and higher analogues) and mode transition algebras over arbitrary rings via the universal enveloping algebra. We prove that these constructions are compatible with base change and give rationality criteria for Möbius vertex algebras over arbitrary fields satisfying mild assumptions. We apply this framework to study Virasoro vertex operator algebras over arbitrary fields. Using integral forms and base change, we extend the rationality of the discrete series Virasoro VOAs from ℂ to arbitrary fields of characteristic zero. In positive characteristic, the Virasoro theory exhibits surprising new phenomena: the so-called restricted Virasoro VOA is C2-cofinite and has a semisimple Zhu algebra, but it is not rational. We also show that this VOA is not simple because it admits nontrivial singular vectors in positive characteristic for every central charge. We calculate the singular vector of degree 2p in characteristics p=5,7 using Mathematica.
Related
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BibTeX
@misc{griffin2026modular,
title = {{Modular Zhu algebra theory and Virasoro vertex algebras}},
author = {Colton Griffin},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.05584},
eprint = {2607.05584},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.05584},
}
RIS
TY - UNPB
TI - Modular Zhu algebra theory and Virasoro vertex algebras
AU - Colton Griffin
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2607.05584
UR - https://arxiv.org/abs/2607.05584
AB - We develop the representation theory of vertex algebras over arbitrary commutative rings as part of a relative theory, suitable for various applications such as the study of modular forms, modular tensor categories, and sheaves of coinvariants and conformal blocks. Towards this end, we construct Zhu algebras (and higher analogues) and mode transition algebras over arbitrary rings via the universal enveloping algebra. We prove that these constructions are compatible with base change and give rationality criteria for Möbius vertex algebras over arbitrary fields satisfying mild assumptions. We apply this framework to study Virasoro vertex operator algebras over arbitrary fields. Using integral forms and base change, we extend the rationality of the discrete series Virasoro VOAs from ℂ to arbitrary fields of characteristic zero. In positive characteristic, the Virasoro theory exhibits surprising new phenomena: the so-called restricted Virasoro VOA is C_2-cofinite and has a semisimple Zhu algebra, but it is not rational. We also show that this VOA is not simple because it admits nontrivial singular vectors in positive characteristic for every central charge. We calculate the singular vector of degree 2p in characteristics p=5,7 using Mathematica.
ER -