Hall algebra multiplication for stable envelopes on bow varieties

Elliptic stable envelopes are fundamental components in the geometric realization of quantum group representations. We present a formula for elliptic stable envelopes on type A Cherkis bow varieties, as a product of simple basic objects in an elliptic cohomology Hall algebra. Combined with the 3d mirror symmetry property of elliptic stable envelopes, our result implies theta function identities for any pair of 01-matrices sharing the same row and column sums.