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Durham University

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Publication details for Anne Taormina

Taormina, Anne & Wendland, Katrin (2020). SU(2) channels the cancellation of K3 BPS states. Journal of High Energy Physics 2020(04): 184.

Author(s) from Durham


The conformal field theoretic elliptic genus, an invariant for N = (2, 2) superconformal field theories, counts the BPS states in any such theory with signs, according
to their bosonic or fermionic nature. For K3 theories, this invariant is the source of the
Mathieu Moonshine phenomenon. There, the net number of 1

  • BPS states is positive for

any conformal dimension above the massless threshold, but it may arise after cancellation
of the contributions of an equal number of bosonic and fermionic BPS states present in
non-generic theories, as is the case for the class of Z2-orbifolds of toroidal SCFTs. Nevertheless, the space Hb of all BPS states that are generic to such orbifold theories provides
a convenient framework to construct a particular generic space of states of K3 theories.
We find a natural action of the group SU(2) on a subspace of Hb which is compatible with
the cancellations of contributions from the corresponding non-generic states. In fact, we
propose that this action channels those cancellations. As a by-product, we find a new
subspace of the generic space of states in Hb.