ADE SUBALGEBRAS OF THE TRIPLET VERTEX ALGEBRA š²(p): D-SERIES
Abstract
We are continuing our study of ADE-orbifold subalgebras of the triplet vertex algebra š²(p) initiated in D. AdamoviÄ, X. Lin and A. Milas, ADE subalgebras of the triplet vertex algebra š²(p): Am-series, Commun. Contemp. Math.15 (2013), Article ID: 1350028, 1ā30. This part deals with the dihedral series. First, subject to a certain constant term identity, we classify all irreducible modules for the vertex algebra , the ā¤2-orbifold of the singlet vertex algebra
. Then, we classify irreducible modules and determine Zhu's and C2-algebra for the vertex algebra š²(p)D2. A general method for construction of twisted š²(p)-modules is also introduced. We also discuss classification of twisted
-modules including the twisted Zhu's algebra
, which is of independent interest. The category of admissible ĪØ-twisted
-modules is expected to be semisimple. We also prove C2-cofiniteness of š²(p)Dm for all m, and give a conjectural list of irreducible š²(p)Dm-modules. Finally, we compute characters of the relevant irreducible modules and describe their modular closure.