Geometry of Massless Scattering in Integrable Superstring
Andrea Fontanella, Alessandro Torrielli
TL;DR
The paper studies massless non-relativistic scattering in AdS/CFT by embedding the massless R-matrix into a q-deformed Poincaré superalgebra, revealing a non-relativistic rapidity $\gamma$ that makes the R-matrix a function of $\gamma_1-\gamma_2$. It shows a $\theta \rightarrow \gamma$ substitution relating relativistic and non-relativistic massless S-matrices, validates this in AdS3 and AdS2 settings for the matrix part and, where possible, the dressing factor, and introduces a geometric, fibre-bundle framework to classify R-matrices via a connection $\Gamma$ and a constant matrix $\mathcal{A}$. The results unify the relativistic and non-relativistic pictures, provide explicit dressing-factor constructions in AdS3 and AdS2, and propose a general program to classify R-matrices by differential-geometric data, with applications to Bethe Ansatz and crossing symmetry.
Abstract
We consider the action of the $q$-deformed Poincaré superalgebra on the massless non-relativistic R-matrix in ordinary (undeformed) integrable $AdS_2 \times S^2 \times T^6$ type IIB superstring theory. The boost generator acts non-trivially on the R-matrix, confirming the existence of a non-relativistic rapidity $γ$ with respect to which the R-matrix must be of difference form. We conjecture that from a massless AdS/CFT integrable relativistic R-matrix one can obtain the parental massless non-relativistic R-matrix simply by replacing the relativistic rapidity with $γ$. We check our conjecture in ordinary (undeformed) $AdS_n \times S^n \times T^{10 - 2n}$, $n = 2, 3$. In the case $n=3$, we check that the matrix part and the dressing factor - up to numerical accuracy for real momenta - obey our prescription. In the $n=2$ case, we check the matrix part and propose the non-relativistic dressing factor. We then start a programme of classifying R-matrices in terms of connections on fibre bundles. The conditions obtained for the connection are tested on a set of known integrable R-matrices.
