Three mod-99 identities from the D4(3)\mathrm{D}_4^{(3)} principal-subspace sum

Let qq be a formal variable, let m1,m20m_1,m_2\geq 0, and define the theta-product notation by θ(a1,,ar;Q)=i=1r(ai;Q)(Q/ai;Q)\theta(a_1,\ldots,a_r;Q)=\prod_{i=1}^r(a_i;Q)_\infty(Q/a_i;Q)_\infty. The mod-99 identities. The following three identities are conjectured:

m1,m20qm12+3m1m2+3m22(q;q)m1(q3;q3)m2=1θ(q,q3;q9),\sum_{m_1,m_2\geq 0}\frac{q^{m_1^2+3m_1m_2+3m_2^2}}{(q;q)_{m_1}(q^3;q^3)_{m_2}}=\frac{1}{\theta(q,q^3;q^9)}, m1,m20qm12+3m1m2+3m22+m1+3m2(q;q)m1(q3;q3)m2=1θ(q2,q3;q9),\sum_{m_1,m_2\geq 0}\frac{q^{m_1^2+3m_1m_2+3m_2^2+m_1+3m_2}}{(q;q)_{m_1}(q^3;q^3)_{m_2}}=\frac{1}{\theta(q^2,q^3;q^9)}, m1,m20qm12+3m1m2+3m22+2m1+3m2(q;q)m1(q3;q3)m2=1θ(q3,q4;q9).\sum_{m_1,m_2\geq 0}\frac{q^{m_1^2+3m_1m_2+3m_2^2+2m_1+3m_2}}{(q;q)_{m_1}(q^3;q^3)_{m_2}}=\frac{1}{\theta(q^3,q^4;q^9)}.

These identities arise from the principal-subspace character of the basic D4(3)\mathrm{D}_4^{(3)} module and were presented in the source as conjectural results. The supplied status gives no resolution evidence, so they remain open here.

Sources & referencesView supporting material

Primary source

Katherine Baker, Shashank Kanade, Matthew C. Russell and Christopher Sadowski, “Principal subspaces of basic modules for twisted affine Lie algebras, q-series multisums, and Nandi's identities”, arXiv:2208.14581 (2022).

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