We show that the normalized supercharacters of principal admissible modules over the affine Lie superalgebra $hat{sell}_{2|1}$ (resp. $hat{psell}_{2|2}$) can be modified, using Zwegers real analytic corrections, to form a modular (resp. $S$-) invaria
nt family of functions. Applying the quantum Hamiltonian reduction, this leads to a new family of positive energy modules over the N=2 (resp. N=4) superconformal algebras with central charge $3(1-frac{2m+2}{M})$, where $m in mathbb{Z}_{geq 0}$, $Min mathbb{Z}_{geq 2}$, $gcd(2m+2,M)=1$ if $m>0$ (resp. $6(frac{m}{M}-1)$, where $m in mathbb{Z}_{geq 1}, Min mathbb{Z}_{geq 2}$, $gcd(2m,M)=1$ if $m>1$), whose modified characters and supercharacters form a modular invariant family.
We classify the finite-dimensional irreducible representations of the Yangians associated with the orthosymplectic Lie superalgebras ${frak{osp}}_{1|2n}$ in terms of the Drinfeld polynomials. The arguments rely on the description of the representatio
ns in the particular case $n=1$ obtained in our previous work.
We show that sheet closures appear as associated varieties of affine vertex algebras. Further, we give new examples of non-admissible affine vertex algebras whose associated variety is contained in the nilpotent cone. We also prove some conjectures f
rom our previous paper and give new examples of lisse affine W-algebras.
We show that the normalized supercharacters of principal admissible modules, associated to each integrable atypical module over the affine Lie superalgebra $widehat{sl}_{2|1}$ can be modified, using Zwegers real analytic corrections, to form an $SL_2
(mathbf{Z})$-invariant family of functions. Using a variation of Zwegers correction, we obtain a similar result for $widehat{osp}_{3|2}$. Applying the quantum Hamiltonian reduction, this leads to new families of positive energy modules over the $N=2$ (resp. $N=3$) superconformal algebras with central charge $c=3 (1-frac{2m+2}{M})$, where $m in mathbf{Z}_{geq 0}, M in mathbf{Z}_{geq 2}$, gcd$(2m+2,M)=1$ if $m>0$ (resp. $c=-3frac{2m+1}{M}$, where $m in mathbf{Z}_{geq 0}, M in mathbf{Z}_{geq 2}$ gcd$(4m +2, M) =1)$, whose modified supercharacters form an $SL_2(mathbf{Z})$-invariant family of functions.
We study modular invariance of normalized supercharacters of tame integrable modules over an affine Lie superalgebra, associated to an arbitrary basic Lie superalgebra $ mathfrak{g}. $ For this we develop a several step modification process of multiv
ariable mock theta functions, where at each step a Zwegers type modifier is used. We show that the span of the resulting modified normalized supercharacters is $ SL_2(mathbb{Z}) $-invariant, with the transformation matrix equal, in the case the Killing form on $mathfrak{g}$ is non-degenerate, to that for the subalgebra $ mathfrak{g}^! $ of $ mathfrak{g}, $ orthogonal to a maximal isotropic set of roots of $ mathfrak{g}. $