Spiralling branes, affine qq-characters and elliptic integrable systems

We apply the spiralling branes technique introduced in arXiv:2312.16990 to many-body integrable systems. We start by giving a new R-matrix description of the trigonometric Ruijsenaars-Schneider (RS) Hamiltonians and eigenfunctions using the intertwiners of quantum toroidal algebra. We then consider elliptic deformations of the RS system, elucidate how Shiraishi functions appear naturally in the process and relate them to certain special infinite system of intertwiners of the algebra. We further show that there are two distinguished elliptic deformations, one of which leads to the conventional elliptic RS Hamiltonians, while the other produces trigonometric Koroteev-Shakirov Hamiltonians. Along the way we prove the fully noncommutative version of the "noncommutative Jacobi identities" for affine qq-characters recently introduced by Grekov and Nekrasov.