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

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=0J(n,n)sdqn/2=(1qL)1/2(1q1/2)(1q1/2L),\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=0χJ(n,n)sdqn/2=(1+q1/2)1/2(1q1/2)3/2,n=0DT(n,n)sdqn/2=(1q1/2)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=0J(n,n)sdqn/2=n=0χJ(n,n)sdqn/2=n=0DT(n,n)sdqn/2=(1+q1/2)1/2(1q1/2)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=0J(n,n)sdqn/2=(1qL1)1/2,\sum_{n=0}^{\infty}\mathrm{J}^{\mathrm{sd}}_{(n,n)}q^{n/2}=(1-q\mathbb{L}^{-1})^{1/2}, n=0χJ(n,n)sdqn/2=n=0DT(n,n)sdqn/2=(1q)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.

Sources & referencesView supporting material

Primary source

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

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