On Superconformal Four-Point Mellin Amplitudes in Dimension $d>2$
Xinan Zhou
TL;DR
This work develops a universal Mellin-space framework to impose the superconformal Ward identities for SCFTs with $3\le d\le 6$, translating position-space constraints into Mellin-space difference equations that govern holographic four-point amplitudes. It implements a two-pronged holographic bootstrap in Mellin space, enabling both finite-pole and infinite-pole analyses, and applies the method to compute new results in $AdS_7\times S^4$ and $AdS_4\times S^7$, including next-next-to-extremal four-point functions, the first one-half BPS four-point function in $AdS_4\times S^7$, and the anomalous dimension of the lowest-dimension $R$-singlet double-trace operator. The results reproduce known AdS$_5\times S^5$ and AdS$_7\times S^4$ results, and yield predictions compatible with large-$C_T$ bootstrap bounds in 3d $\mathcal{N}=8$, providing a robust, scalable route to holographic correlators beyond traditional Witten-diagram methods. Overall, the paper showcases a universal, dimension-agnostic approach to holographic four-point functions that aligns with bootstrap constraints and enhances the computational toolkit for maximally supersymmetric AdS/CFT setups.
Abstract
We present a universal treatment for imposing superconformal constraints on Mellin amplitudes for $\mathrm{SCFT_d}$ with $3\leq d\leq 6$. This leads to a new technique to compute holographic correlators, which is similar but complementary to the ones introduced in [1,2]. We apply this technique to theories in various spacetime dimensions. In addition to reproducing known results, we obtain a simple expression for next-next-to-extremal four-point functions in $AdS_7\times S^4$. We also use this machinery on $AdS_4\times S^7$ and compute the first holographic one-half BPS four-point function. We extract the anomalous dimension of the R-symmetry singlet double-trace operator with the lowest conformal dimension and find agreement with the 3d $\mathcal{N}=8$ numerical bootstrap bound at large central charge.
