arXiv subjects

Iustin Surubaru

Publications and source records attributed to Iustin Surubaru.

5 recordsLinked to original sources

arXiv2026

Five-dimensional Geometry from Spinning Amplitudes

Massive spinor-helicity variables in four dimensions are a useful tool for studying amplitudes between higher-spin fields and gravitons. Among them a special, simple set of amplitudes reproduces the linearized stress-energy tensor of a Kerr black hole in the classical limit. In this work we initiate the study of the classical limit of three-point spinor-helicity amplitudes in five dimensions. We introduce the map between the spinor invariants and the expectation values of spin operators and match the amplitude building blocks with those of the multipole expansion. Interestingly, in order to take the classical limit of a general amplitude, we need to augment the multipole structures with the Hodge dual of the classical spin tensor. We study the classical limit of alternative spinning states not described by fully-symmetric products of polarisations and conclude that they can describe the same spacetimes. Finally, by relaxing the orthogonality condition of the spin tensor we are able to model spacetimes with a single rotational isometry and match these to the classical limit of amplitudes allowing for an internal spin shift. Along the way we also identify the class of amplitudes describing the Myers-Perry black hole and comment on its generalization to arbitrary dimensions.

hep-th↗

arXiv2026

From AdS correlators to Carrollian amplitudes with the scattering equation

The scattering equations relate massless scattering kinematics to marked points on a Riemann sphere, and underpin remarkable formulae for the full tree-level S-matrices of many interesting QFTs, including cubic biadjoint scalars, Yang-Mills theory and general relativity. The scattering equations arise from worldsheet correlators of ambitwistor string theories, which has enabled their generalisation to anti-de Sitter (AdS) space in certain cases. In this paper, we use the scattering equations and ambitwistor strings to prove the correspondence between an appropriate flat limit of boundary correlators in AdS and Carrollian scattering amplitudes -- massless amplitudes written in position space on the null conformal boundary -- for any number of external states and spacetime dimensions in tree-level, cubic scalar theories. We first derive the Carrollian version of the scattering equations in Minkowski space and their associated Carrollian amplitude formulae, by direct Fourier transform from momentum space and from ambitwistor strings with a Carrollian basis of vertex operators. We then take the flat limit of known formulae for all tree-level boundary correlators of cubic scalar theories in AdS, recovering the Carrollian amplitudes in flat space. In the special case of AdS$_3$, we also make some comments on the flat space limit of spinning boundary correlators.

hep-th↗

arXiv2025

Twistorial chiral algebras in higher dimensions

In four spacetime dimensions, the classically integrable self-dual sectors of gauge theory and gravity have associated chiral algebras, which emerge naturally from their description in twistor space. We show that there are similar chiral algebras associated to integrable sectors of gauge theory and gravity whenever the spacetime dimension is an integer multiple of four. In particular, the hyperkähler sector of gravity and the hyperholomorphic sector of gauge theory in $4m$-dimensions have well-known twistor descriptions giving rise to chiral algebras. Using twistor sigma models to describe these sectors, we demonstrate that the chiral algebras in higher-dimensions also arise as soft symmetry algebras under a certain notion of collinear limit. Interestingly, the chiral algebras and collinear limits in higher-dimensions are defined on the 2-sphere, rather than the full celestial sphere.

hep-th↗

arXiv2025

Conformal blocks from celestial graviton amplitudes

Four-point gluon and graviton correlators in celestial holography are famously non-analytic, having distributional support. In this work, we propose an alternative graviton correlator that is analytic and displays several desirable properties. We compute the four-point correlator involving one graviton shadow operator and three graviton primary operators from the celestial four-point graviton amplitudes at tree-level. We perform the conformal block decomposition for the shadow correlator in the compatible channel. For the case when the shadow operator is conformally soft, we compute the single-valued completion of the shadow correlator and perform the conformal block decomposition of the single-valued shadow correlator in all channels. We find an integral representation of the single-valued shadow correlator, which allows us to invert the shadow transform to find the single-valued celestial graviton amplitude. We study various properties of the single-valued celestial graviton amplitude. Interestingly, it exhibits a double copy structure in relation to its counterpart gluon amplitude.

hep-th↗

arXiv2025

Carrollian Amplitudes and Holographic Correlators in AdS3/CFT2

We study Carrollian amplitudes of massless scalars in (1+2) Minkowski space. Using the prescription recently shown by Alday et al. [JHEP 03 (2025) 158] originally designed for the AdS4 Witten diagrams, we show that AdS3 Witten diagrams in position space in the flat space limit reduce to Carrollian amplitudes. The flat space limit in the bulk is implemented by the Carrollian limit at the boundary. Focusing on four-point correlators with contact and exchange diagrams, we show that the Carrollian limit makes the universality of the bulk point singularity manifest upon performing analytic continuation to the Lorentzian signature of the boundary correlators. Unlike four-point Carrollian amplitudes in (1+3) dimensions, the (1+2) dimensional ones are non-distributional, having analytic properties simpler than the AdS correlators. We also observe for the first time a double copy structure of Carrollian amplitudes.

hep-th↗