A new theoretical analysis reports that a supersymmetric index in matrix theory reproduces a class of single-minus graviton amplitudes in a special supersymmetric kinematic region. The result is presented for selected charge configurations.
The paper is an arXiv version 1 preprint dated 25 August 2026.
Turning the matrix model into a scattering calculation
After compactifying one transverse direction, T-duality converts BFSS into maximally supersymmetric 1 + 1-dimensional U(N) Yang–Mills theory, the form used for the matrix-string analysis.
The theoretical configuration is organized into n−1 incoming blocks, each of size N_i. The authors use a supersymmetric index, a way of counting BPS states on the Coulomb branch of four-dimensional N=4 super Yang–Mills, to construct the single-minus amplitude.
The general-n result uses repeated BPS wall crossing, tracking the index as the charges are considered in different chambers. In the selected chamber, the resulting index recovers the gravity expression used for comparison.
Agreement reaches a soft limit and a plane wave
At finite values of the charges N_i and n_i, the paper reports complete agreement between the index and BFSS calculation and the corresponding gravity result in the stated chamber. The paper presents that agreement under explicit assumptions.
Wall crossing also gives a soft-symmetry relation. Requiring two wall-crossing paths to produce the same result yields the momentum-space w1+∞ Ward identity for single-minus amplitudes. The identity is formulated in a soft limit, where the relevant charge is taken to be sufficiently small.
The scope of that identity is narrow. It is stated to hold exactly only for sufficiently small soft charges, within an open neighborhood of n_s=N_s=0. The analysis does not establish the same exact statement for arbitrary soft deformations.
In the separate plane-wave case, the momenta lie at the boundary of the selected chamber and only the brackets [n−1,a] survive. Only the U(1) center-of-mass degree of freedom contributes, making the matrix calculation identical to the corresponding gravity calculation.
What the calculation does not settle
One key assumption is the direct use of Sen's wall-crossing methods in the two-dimensional field-theory problem. The paper says that this application is assumed and that a proof would be of interest.
The general calculation explicitly evaluates only one particularly simple external-momentum chamber, with extension to all chambers left as an expectation. It is also restricted to primitive vectors for the external lines and all possible internal lines, so nonprimitive cases remain unexamined.
Those limits mean that the reported agreement applies to the stated chamber and charge class. It does not establish the index-amplitude correspondence in every external-charge chamber or for nonprimitive charge vectors.
Funding included U.S. Department of Energy grants DE-SC0009988 and DE-SC0007870, National Science Foundation grants AST-2307888 and PHY-2340457, and a Simons Foundation grant. The acknowledgments also state that an internal OpenAI model assisted with parts of the analysis, numerical-factor checks and copy editing, while the human authors supplied the ideas, arguments and writing.
Paper data and sources
Original title: Single-Minus Graviton Amplitudes from Matrix Theory
Authors: Alfredo Guevara, Alexandru Lupsasca, Juan Maldacena, Andrew Strominger
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-25
DOI: Not available
Original paper · Full text