Generating-series conjecture for the self-dual \tilde{A}_1 quiver

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Let Q=(∙⇉∙)Q=(\bullet\rightrightarrows\bullet) be the self-dual A~1\tilde{A}_1 quiver with its two vertices exchanged by the contravariant involution, and write A~1u,v\tilde{A}_1^{u,v} for the indicated vertex and edge signs. Let L\mathbb{L} be the Lefschetz motive, qq a formal variable, and Jsd\mathrm{J}^{\mathrm{sd}}, χJsd\frac{\chi}{\mathrm{J}}^{\mathrm{sd}}, and DTsd\mathrm{DT}^{\mathrm{sd}} the motivic, numerical, and Donaldson--Thomas self-dual invariants. Generating-series conjecture for the self-dual A~1\tilde{A}_1 quiver. In the situation above, the following identities should hold:

For A~1+,++\tilde{A}_1^{+,++} and A~1−,−−\tilde{A}_1^{-,--},

∑n=0∞J(n,n)sdqn/2=(1−qL)1/2(1−q1/2)(1−q1/2L),\sum_{n=0}^{\infty}\mathrm{J}^{\mathrm{sd}}_{(n,n)}q^{n/2}=\frac{(1-q\mathbb{L})^{1/2}}{(1-q^{1/2})(1-q^{1/2}\mathbb{L})}, ∑n=0∞χJ(n,n)sdqn/2=(1+q1/2)1/2(1−q1/2)3/2,∑n=0∞DT(n,n)sdqn/2=(1−q1/2)1/2(1+q1/2)3/2.\sum_{n=0}^{\infty}\frac{\chi}{\mathrm{J}}^{\mathrm{sd}}_{(n,n)}q^{n/2}=\frac{(1+q^{1/2})^{1/2}}{(1-q^{1/2})^{3/2}},\qquad \sum_{n=0}^{\infty}\mathrm{DT}^{\mathrm{sd}}_{(n,n)}q^{n/2}=\frac{(1-q^{1/2})^{1/2}}{(1+q^{1/2})^{3/2}}.

For A~1+,+−\tilde{A}_1^{+,+-} and A~1−,+−\tilde{A}_1^{-,+-}, all three generating series are equal to

∑n=0∞J(n,n)sdqn/2=∑n=0∞χJ(n,n)sdqn/2=∑n=0∞DT(n,n)sdqn/2=(1+q1/2)1/2(1−q1/2)1/2.\sum_{n=0}^{\infty}\mathrm{J}^{\mathrm{sd}}_{(n,n)}q^{n/2}=\sum_{n=0}^{\infty}\frac{\chi}{\mathrm{J}}^{\mathrm{sd}}_{(n,n)}q^{n/2}=\sum_{n=0}^{\infty}\mathrm{DT}^{\mathrm{sd}}_{(n,n)}q^{n/2}=\frac{(1+q^{1/2})^{1/2}}{(1-q^{1/2})^{1/2}}.

For A~1+,−−\tilde{A}_1^{+,--} and A~1−,++\tilde{A}_1^{-,++},

∑n=0∞J(n,n)sdqn/2=(1−qL−1)1/2,\sum_{n=0}^{\infty}\mathrm{J}^{\mathrm{sd}}_{(n,n)}q^{n/2}=(1-q\mathbb{L}^{-1})^{1/2}, ∑n=0∞χJ(n,n)sdqn/2=∑n=0∞DT(n,n)sdqn/2=(1−q)1/2.\sum_{n=0}^{\infty}\frac{\chi}{\mathrm{J}}^{\mathrm{sd}}_{(n,n)}q^{n/2}=\sum_{n=0}^{\infty}\mathrm{DT}^{\mathrm{sd}}_{(n,n)}q^{n/2}=(1-q)^{1/2}.

These identities are suggested by numerical computations for the two-arrow quiver; the supplied source gives no resolution status.

References

Primary source

Chenjing Bu, “Enumerative invariants in self-dual categories. I. Motivic invariants”, arXiv:2302.00038 (2025).

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