How are pseudo-$q$-traces related to (co)ends?
Abstract
Let be an -graded -cofinite vertex operator algebra (VOA), not necessarily rational or self-dual. Using a special case of the sewing-factorization theorem from [GZ25a], we show that the end in (where is the contragredient module of ) admits a natural structure of associative -algebra compatible with its -module structure. Moreover, we show that a suitable category of left -modules is isomorphic, as a linear category, to , and that the space of vacuum torus conformal blocks is isomorphic to the space of symmetric linear functionals on . Combining these results with the main theorem of [GZ25b], we prove a conjecture of Gainutdinov-Runkel: For any projective generator in , the pseudo--trace construction yields a linear isomorphism from to the space of vacuum torus conformal blocks of . In particular, if is a unital finite-dimensional -algebra such that the category of finite-dimensional left -modules is equivalent to , then is linearly isomorphic to the space of vacuum torus conformal blocks of . This confirms a conjecture of Arike-Nagatomo.
Cite
@article{arxiv.2508.04532,
title = {How are pseudo-$q$-traces related to (co)ends?},
author = {Bin Gui and Hao Zhang},
journal= {arXiv preprint arXiv:2508.04532},
year = {2025}
}
Comments
64 pages, many figures