Let q 1 , q 2 , u , Z q_1,q_2,u,Z q 1 , q 2 , u , Z satisfy ∣ q 2 ∣ < 1 < ∣ q 1 ∣ |q_2|<1<|q_1| ∣ q 2 ∣ < 1 < ∣ q 1 ∣ . Define
F ^ d ( u , q 1 , q 2 ∣ Z ) = ∑ 2 n ∈ Z u 2 d n ( q 1 q 2 ) 4 d n 2 Z 2 n 2 ( u q 1 4 n − 2 , u − 1 q 1 − 4 n − 2 ) ∞ ( 1 ) ( u q 1 − 1 q 2 4 n + 1 , u − 1 q 1 − 1 q 2 − 4 n + 1 ) ∞ ( 2 ) F n ( 1 ) ( q 1 2 d Z ) F n ( 2 ) ( q 2 2 d Z ) , \widehat{\mathcal{F}}_d(u,q_1,q_2|Z)=\sum_{2n\in\mathbb{Z}}\frac{u^{2dn}(q_1q_2)^{4dn^2}Z^{2n^2}}{(uq_1^{4n-2},u^{-1}q_1^{-4n-2})^{(1)}_\infty(uq_1^{-1}q_2^{4n+1},u^{-1}q_1^{-1}q_2^{-4n+1})^{(2)}_\infty}\mathcal{F}^{(1)}_n(q_1^{2d}Z)\mathcal{F}^{(2)}_n(q_2^{2d}Z), F d ( u , q 1 , q 2 ∣ Z ) = 2 n ∈ Z ∑ ( u q 1 4 n − 2 , u − 1 q 1 − 4 n − 2 ) ∞ ( 1 ) ( u q 1 − 1 q 2 4 n + 1 , u − 1 q 1 − 1 q 2 − 4 n + 1 ) ∞ ( 2 ) u 2 d n ( q 1 q 2 ) 4 d n 2 Z 2 n 2 F n ( 1 ) ( q 1 2 d Z ) F n ( 2 ) ( q 2 2 d Z ) ,
where
F n ( 1 ) ( z ) = F ( u q 1 4 n , q 1 2 , q 1 − 1 q 2 ∣ z ) , F n ( 2 ) ( z ) = F ( u q 2 4 n , q 1 q 2 − 1 , q 2 2 ∣ z ) . \mathcal{F}^{(1)}_n(z)=\mathcal{F}(uq_1^{4n},q_1^2,q_1^{-1}q_2|z),\qquad \mathcal{F}^{(2)}_n(z)=\mathcal{F}(uq_2^{4n},q_1q_2^{-1},q_2^2|z). F n ( 1 ) ( z ) = F ( u q 1 4 n , q 1 2 , q 1 − 1 q 2 ∣ z ) , F n ( 2 ) ( z ) = F ( u q 2 4 n , q 1 q 2 − 1 , q 2 2 ∣ z ) .
Also define
F ◊ ( u , q 1 , q 2 ∣ Z ) = ∑ λ 1 , λ 2 Z ∣ λ 1 ∣ + ∣ λ 2 ∣ 2 1 ∏ i , j = 1 2 N λ i , λ j N S ( q 1 , q 2 , u i / u j ) . \mathcal{F}_{\lozenge}(u,q_1,q_2|Z)=\sum_{\lambda_1,\lambda_2}Z^{\frac{|\lambda_1|+|\lambda_2|}{2}}\frac{1}{\prod_{i,j=1}^2N^{\mathrm{NS}}_{\lambda_i,\lambda_j}(q_1,q_2,u_i/u_j)}. F ◊ ( u , q 1 , q 2 ∣ Z ) = λ 1 , λ 2 ∑ Z 2 ∣ λ 1 ∣ + ∣ λ 2 ∣ ∏ i , j = 1 2 N λ i , λ j NS ( q 1 , q 2 , u i / u j ) 1 .
The source defines the factors N λ , μ ◊ N^{\lozenge}_{\lambda,\mu} N λ , μ ◊ using the subsets of boxes selected by the stated parity condition.
Generic bilinear relation.
F ◊ ( u , q 1 , q 2 ∣ Z ) = F ^ 1 ( u , q 1 , q 2 ∣ Z ) , F ◊ ( u , q 1 , q 2 ∣ Z ) = ( 1 − q 2 q 1 Z 1 / 2 ) F ^ 0 ( u , q 1 , q 2 ∣ Z ) . \mathcal{F}_{\lozenge}(u,q_1,q_2|Z)=\widehat{\mathcal{F}}_1(u,q_1,q_2|Z),\qquad \mathcal{F}_{\lozenge}(u,q_1,q_2|Z)=(1-q_2q_1Z^{1/2})\widehat{\mathcal{F}}_0(u,q_1,q_2|Z). F ◊ ( u , q 1 , q 2 ∣ Z ) = F 1 ( u , q 1 , q 2 ∣ Z ) , F ◊ ( u , q 1 , q 2 ∣ Z ) = ( 1 − q 2 q 1 Z 1/2 ) F 0 ( u , q 1 , q 2 ∣ Z ) .
This extends the bilinear relations from q 1 = q − 1 q_1=q^{-1} q 1 = q − 1 and q 2 = q q_2=q q 2 = q to generic parameters in the indicated sector; the supplied text gives no separate resolution status.