English

How are pseudo-$q$-traces related to (co)ends?

Quantum Algebra 2025-08-07 v1 Mathematical Physics math.MP Representation Theory

Abstract

Let V\mathbb V be an N\mathbb N-graded C2C_2-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 E=MMod(V)MCM\mathbb E=\int_{\mathbb M\in\mathrm{Mod}(\mathbb V)}\mathbb M\otimes_{\mathbb C}\mathbb M' in Mod(V2)\mathrm{Mod}(\mathbb{V}^{\otimes2}) (where M\mathbb{M}' is the contragredient module of M\mathbb{M}) admits a natural structure of associative C\mathbb C-algebra compatible with its V2\mathbb{V}^{\otimes2}-module structure. Moreover, we show that a suitable category CohL(E)\mathrm{Coh}_{\mathrm{L}}(\mathbb E) of left E\mathbb E-modules is isomorphic, as a linear category, to Mod(V)\mathrm{Mod}(\mathbb V), and that the space of vacuum torus conformal blocks is isomorphic to the space SLF(E)\mathrm{SLF}(\mathbb E) of symmetric linear functionals on E\mathbb E. Combining these results with the main theorem of [GZ25b], we prove a conjecture of Gainutdinov-Runkel: For any projective generator G\mathbb G in Mod(V)\mathrm{Mod}(\mathbb V), the pseudo-qq-trace construction yields a linear isomorphism from SLF(EndV(G)opp)\mathrm{SLF}(\mathrm{End}_{\mathbb V}(\mathbb{G})^{\mathrm{opp}}) to the space of vacuum torus conformal blocks of V\mathbb V. In particular, if AA is a unital finite-dimensional C\mathbb C-algebra such that the category of finite-dimensional left AA-modules is equivalent to Mod(V)\mathrm{Mod}(\mathbb V), then SLF(A)\mathrm{SLF}(A) is linearly isomorphic to the space of vacuum torus conformal blocks of V\mathbb V. This confirms a conjecture of Arike-Nagatomo.

Keywords

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