Observing Massive Scattering from Null Infinity
Pith reviewed 2026-06-29 01:53 UTC · model grok-4.3
The pith
Continuity between timelike and null infinity lets the late-time Bondi mass aspect detect massive outgoing radiation.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Continuity between the boundaries of timelike and null infinity implies that the late-time limit of the Bondi mass aspect naturally acts as a detector operator for massive outgoing radiation. In-in correlation functions of the Bondi mass aspect at I^+_+ relate to weighted sums of scattering cross sections, implying that an observer at I can extract information about massive scattering processes at late times. The Bondi mass aspect is interpreted as a Carrollian stress-tensor component, and Ward identities are studied to constrain its two-point functions.
What carries the argument
The late-time limit of the Bondi mass aspect at null infinity, acting as a detector operator for massive outgoing radiation carried by soft gravitons.
If this is right
- In-in correlators of the Bondi mass aspect at late times encode weighted sums of massive scattering cross sections.
- Observers at null infinity gain access to information about massive scattering amplitudes.
- The Carrollian stress-tensor interpretation yields Ward identities that constrain the two-point functions of the mass aspect.
- Soft graviton radiation transmits details of massive processes to the null boundary.
Where Pith is reading between the lines
- The construction offers a route to include massive external states in existing null-infinity holographic setups.
- Similar continuity arguments could link other asymptotic charges to massive scattering data.
- The detector-operator interpretation suggests concrete checks against known massive scattering amplitudes in controlled limits.
Load-bearing premise
Continuity between the boundaries of timelike and null infinity directly maps the late-time Bondi mass aspect to a detector for massive outgoing states.
What would settle it
An explicit computation or measurement showing that the in-in correlation functions of the late-time Bondi mass aspect do not reproduce the predicted weighted sums of scattering cross sections.
Figures
read the original abstract
Because massive particles asymptote to timelike rather than null infinity, current flat space holographic proposals such as celestial or Carrollian holography struggle to describe scattering processes with massive external states. We take a step toward addressing this limitation by studying how information about massive scattering amplitudes is carried to the late-time limit of null infinity by soft graviton radiation. We show that continuity between the boundaries of timelike and null infinity implies that the late-time limit of the Bondi mass aspect naturally acts as a detector operator for massive outgoing radiation. We further relate in-in correlation functions of the Bondi mass aspect at $\mathscr{I}^+_+$ to weighted sums of scattering cross sections, implying that an observer at $\mathscr{I}$ can extract information about massive scattering processes at late times. Finally, we interpret the Bondi mass aspect as a Carrollian stress-tensor component, and study Ward identities to constrain its two-point functions.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper addresses the challenge of incorporating massive external states into flat-space holographic proposals like celestial and Carrollian holography. It argues that continuity between timelike and null infinity allows the late-time limit of the Bondi mass aspect to function as a detector operator for massive outgoing radiation carried by soft gravitons. The manuscript further claims that in-in correlation functions of the Bondi mass aspect at I^+_+ correspond to weighted sums of scattering cross sections, enabling extraction of massive scattering information at late times, and interprets the Bondi mass aspect as a Carrollian stress-tensor component whose two-point functions are constrained by Ward identities.
Significance. If the continuity mapping and resulting correlator relations hold with explicit derivations, the result would provide a concrete bridge between massive scattering amplitudes and null-infinity observables, extending current holographic frameworks without introducing new free parameters. The Ward-identity analysis for the Carrollian interpretation offers a falsifiable constraint on two-point functions that could be checked against known soft theorems.
major comments (2)
- [Abstract] Abstract and the opening of the main argument: the central claim that 'continuity between the boundaries of timelike and null infinity implies that the late-time limit of the Bondi mass aspect naturally acts as a detector operator' is stated without an explicit asymptotic matching (e.g., relating the fall-off of massive fields at timelike infinity to the Bondi mass aspect at I^+_+) or a citation to a specific prior result establishing the required continuity in the relevant regime. This step is load-bearing for the subsequent identification of in-in correlators with scattering cross sections.
- [Section deriving correlator-cross-section relation] The section deriving the relation between in-in correlators of the Bondi mass aspect and weighted sums of cross sections: without the explicit continuity map secured in the preceding step, the identification reduces to a formal re-expression whose physical content cannot be assessed; an error estimate or check against a known massive amplitude (e.g., tree-level scalar scattering) would be required to confirm the weighting.
minor comments (1)
- [Abstract] Notation for the late-time limit I^+_+ should be defined once at first use and used consistently; the distinction between I^+ and I^+_+ is not immediately clear from the abstract alone.
Simulated Author's Rebuttal
We thank the referee for their detailed review and valuable suggestions. We address each major comment below and will incorporate revisions to enhance the clarity and rigor of the manuscript, particularly regarding the asymptotic continuity and the validation of the correlator relations.
read point-by-point responses
-
Referee: [Abstract] Abstract and the opening of the main argument: the central claim that 'continuity between the boundaries of timelike and null infinity implies that the late-time limit of the Bondi mass aspect naturally acts as a detector operator' is stated without an explicit asymptotic matching (e.g., relating the fall-off of massive fields at timelike infinity to the Bondi mass aspect at I^+_+) or a citation to a specific prior result establishing the required continuity in the relevant regime. This step is load-bearing for the subsequent identification of in-in correlators with scattering cross sections.
Authors: We appreciate the referee highlighting the importance of making the continuity argument explicit. The manuscript builds on established results in the literature concerning the asymptotic behavior at timelike and null infinity, but we agree that a more direct exposition would improve accessibility. In the revised manuscript, we will add an explicit derivation of the asymptotic matching in Section 2 (or a new subsection), relating the fall-off of massive fields at timelike infinity to the late-time Bondi mass aspect at I^+. We will also include relevant citations to prior works on this continuity. This will secure the foundation for the subsequent claims. revision: yes
-
Referee: [Section deriving correlator-cross-section relation] The section deriving the relation between in-in correlators of the Bondi mass aspect and weighted sums of cross sections: without the explicit continuity map secured in the preceding step, the identification reduces to a formal re-expression whose physical content cannot be assessed; an error estimate or check against a known massive amplitude (e.g., tree-level scalar scattering) would be required to confirm the weighting.
Authors: We concur that an explicit check is necessary to substantiate the physical interpretation. Upon revision, we will include in the relevant section a concrete example using tree-level scalar scattering amplitudes. This will involve computing the in-in correlator and comparing it to the known cross section, providing an error estimate for the late-time approximation. Such a check will confirm the weighting factors and demonstrate the robustness of the relation. revision: yes
Circularity Check
No significant circularity; derivation presented as independent step from continuity assumption.
full rationale
The paper states it 'shows' that continuity between timelike and null infinity implies the late-time Bondi mass aspect acts as a detector, then relates in-in correlators to cross sections and interprets the mass aspect as a Carrollian stress-tensor component. No equations or steps are exhibited that reduce by construction to fitted inputs, self-definitions, or unverified self-citations. The continuity mapping is invoked as an assumption with the 'show' treated as a new derivation; the Carrollian interpretation is an additional interpretive step rather than load-bearing foundation. Absent explicit reduction in the text to prior overlapping-author results by definition, the chain is self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Continuity between the boundaries of timelike and null infinity allows the late-time Bondi mass aspect to act as a detector for massive outgoing radiation
Reference graph
Works this paper leans on
-
[1]
Flat Space Amplitudes and Conformal Symmetry of the Celestial Sphere
S. Pasterski, S.-H. Shao, and A. Strominger,Flat space amplitudes and conformal symmetry of the celestial sphere,Phys. Rev.D96(2017), no. 6 065026, [arXiv:1701.00049]. 28
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[2]
S. Pasterski, M. Pate, and A.-M. Raclariu,Celestial Holography, in2022 Snowmass Summer Study, 11, 2021.arXiv:2111.11392
-
[3]
Ruzziconi,Carrollian physics and holography,Phys
R. Ruzziconi,Carrollian physics and holography,Phys. Rept.1182(2026) 1–87, [arXiv:2602.02644]
-
[4]
A Conformal Basis for Flat Space Amplitudes
S. Pasterski and S.-H. Shao,Conformal basis for flat space amplitudes,Phys. Rev.D96 (2017), no. 6 065022, [arXiv:1705.01027]
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[5]
Gluon Amplitudes as 2d Conformal Correlators
S. Pasterski, S.-H. Shao, and A. Strominger,Gluon amplitudes as 2d conformal correlators, Phys. Rev.D96(2017), no. 8 085006, [arXiv:1706.03917]
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[6]
M. Pate, A.-M. Raclariu, A. Strominger, and E. Y. Yuan,Celestial Operator Products of Gluons and Gravitons,arXiv:1910.07424
-
[7]
M. Pate, A.-M. Raclariu, and A. Strominger,Conformally soft theorem in gauge theory, Phys. Rev.D100(2019), no. 8 085017, [arXiv:1904.10831]
-
[8]
Puhm,Conformally soft theorem in gravity,JHEP09(2020) 130, [arXiv:1905.09799]
A. Puhm,Conformally soft theorem in gravity,JHEP09(2020) 130, [arXiv:1905.09799]
-
[9]
Conformally Soft Photons and Gravitons
L. Donnay, A. Puhm, and A. Strominger,Conformally soft photons and gravitons,JHEP 01(2019) 184, [arXiv:1810.05219]
work page internal anchor Pith review Pith/arXiv arXiv 2019
-
[10]
A. Guevara, E. Himwich, M. Pate, and A. Strominger,Holographic symmetry algebras for gauge theory and gravity,JHEP11(2021) 152, [arXiv:2103.03961]
-
[11]
Strominger,w 1+∞ Algebra and the Celestial Sphere: Infinite Towers of Soft Graviton, Photon, and Gluon Symmetries,Phys
A. Strominger,w 1+∞ Algebra and the Celestial Sphere: Infinite Towers of Soft Graviton, Photon, and Gluon Symmetries,Phys. Rev. Lett.127(2021), no. 22 221601
2021
-
[12]
K. Costello, N. M. Paquette, and A. Sharma,Top-Down Holography in an Asymptotically Flat Spacetime,Phys. Rev. Lett.130(2023), no. 6 061602, [arXiv:2208.14233]
-
[13]
K. Costello, N. M. Paquette, and A. Sharma,Burns space and holography,JHEP10 (2023) 174, [arXiv:2306.00940]
-
[14]
Carrollian Perspective on Celestial Holography
L. Donnay, A. Fiorucci, Y. Herfray, and R. Ruzziconi,Carrollian Perspective on Celestial Holography,Phys. Rev. Lett.129(2022), no. 7 071602, [arXiv:2202.04702]
work page internal anchor Pith review Pith/arXiv arXiv 2022
- [15]
- [16]
- [17]
-
[18]
R. Ruzziconi and A. Saha,Holographic Carrollian currents for massless scattering,JHEP 01(2025) 169, [arXiv:2411.04902]
-
[19]
P. Kraus and R. M. Myers,Carrollian partition function for bulk Yang-Mills theory,JHEP 08(2025) 180, [arXiv:2503.00916]
-
[20]
J. Isen, P. Kraus, R. Monten, and R. M. Myers,The gravitational S-matrix from the path integral: asymptotic symmetries and soft theorems,arXiv:2603.17045
work page internal anchor Pith review Pith/arXiv arXiv
- [21]
- [22]
- [23]
-
[24]
A. Lipstein, R. Ruzziconi, and A. Yelleshpur Srikant,Towards a flat space Carrollian hologram from AdS4/CFT3,JHEP06(2025) 073, [arXiv:2504.10291]
-
[25]
P. Kraus and R. M. Myers,Carrollian partition functions and the flat limit of AdS,JHEP 01(2025) 183, [arXiv:2407.13668]
-
[26]
H. Kulkarni, R. Ruzziconi, and A. Yelleshpur Srikant,On Carrollian and celestial correlators in general dimensions,JHEP10(2025) 187, [arXiv:2508.06602]
-
[27]
R. Marotta, A. Shekar, and M. Verma,Carrollian Conformal Theories in Momentum Space,arXiv:2512.06881
- [28]
-
[29]
Towards a Carrollian Description of Yang-Mills
J. Opreij, D. Skinner, and H. Wang,Towards a Carrollian Description of Yang-Mills, arXiv:2604.09771
work page internal anchor Pith review Pith/arXiv arXiv
-
[30]
J. de Boer, J. Hartong, N. A. Obers, W. Sybesma, and S. Vandoren,Carroll stories,JHEP 09(2023) 148, [arXiv:2307.06827]. 30
- [31]
- [32]
- [33]
-
[34]
E. Himwich and M. Pate,w 1+∞ in 4D gravitational scattering,JHEP07(2024) 180, [arXiv:2312.08597]
-
[35]
J. Kulp and S. Pasterski,Multiparticle states for the flat hologram,JHEP08(2025) 091, [arXiv:2501.00462]
-
[36]
Operator Product Expansion in Carrollian CFT
K. Nguyen and J. Salzer,Operator product expansion in Carrollian CFT,JHEP07(2025) 193, [arXiv:2503.15607]
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[37]
R. Ruzziconi and P. West,Extended BMS representations and strings,JHEP05(2026) 167, [arXiv:2601.00662]
- [38]
-
[39]
A. Fiorucci, S. Pekar, P. Marios Petropoulos, and M. Vilatte,Carrollian-Holographic Derivation of Gravitational Flux-Balance Laws,Phys. Rev. Lett.135(2025), no. 26 261602, [arXiv:2505.00077]
-
[40]
J. Hartong, E. Have, V. Nenmeli, and G. Oling,Boundary Energy-Momentum Tensors for Asymptotically Flat Spacetimes,arXiv:2505.05432
-
[41]
S. Caron-Huot, M. Giroux, H. S. Hannesdottir, and S. Mizera,What can be measured asymptotically?,JHEP01(2024) 139, [arXiv:2308.02125]
-
[42]
E. Herrmann, M. Kologlu, and I. Moult,Energy Correlators in Perturbative Quantum Gravity,arXiv:2412.05384
-
[43]
S. Caron-Huot, M. Giroux, H. S. Hannesdottir, and S. Mizera,Crossing beyond scattering amplitudes,JHEP04(2024) 060, [arXiv:2310.12199]
- [44]
- [45]
-
[46]
G. Comp` ere, S. E. Gralla, and H. Wei,An asymptotic framework for gravitational scattering,Class. Quant. Grav.40(2023), no. 20 205018, [arXiv:2303.17124]
-
[47]
Relaxing the Parity Conditions of Asymptotically Flat Gravity
G. Compere and F. Dehouck,Relaxing the Parity Conditions of Asymptotically Flat Gravity,Class. Quant. Grav.28(2011) 245016, [arXiv:1106.4045]. [Erratum: Class.Quant.Grav. 30, 039501 (2013)]
work page internal anchor Pith review Pith/arXiv arXiv 2011
-
[48]
The BMS4 algebra at spatial infinity
C. Troessaert,The BMS4 algebra at spatial infinity,Class. Quant. Grav.35(2018), no. 7 074003, [arXiv:1704.06223]
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[49]
BMS Group at Spatial Infinity: the Hamiltonian (ADM) approach
M. Henneaux and C. Troessaert,BMS Group at Spatial Infinity: the Hamiltonian (ADM) approach,JHEP03(2018) 147, [arXiv:1801.03718]
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[50]
K. Prabhu,Conservation of asymptotic charges from past to future null infinity: supermomentum in general relativity,JHEP03(2019) 148, [arXiv:1902.08200]
work page internal anchor Pith review Pith/arXiv arXiv 2019
- [51]
-
[52]
A proof of conservation laws in gravitational scattering: tails and breaking of peeling
G. Comp` ere and S. Robert,A proof of conservation laws in gravitational scattering: tails and breaking of peeling,arXiv:2603.08705
work page internal anchor Pith review Pith/arXiv arXiv
-
[53]
G. Boschetti and M. Campiglia,An asymptotic proof of the classical log soft graviton theorem,arXiv:2603.09844
-
[54]
Asymptotic symmetries of gravity and soft theorems for massive particles
M. Campiglia and A. Laddha,Asymptotic symmetries of gravity and soft theorems for massive particles,JHEP12(2015) 094, [arXiv:1509.01406]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[55]
S. Agrawal, L. Donnay, K. Nguyen, and R. Ruzziconi,Logarithmic soft graviton theorems from superrotation Ward identities,JHEP02(2024) 120, [arXiv:2309.11220]
-
[56]
Null to time-like infinity Green's functions for asymptotic symmetries in Minkowski spacetime
M. Campiglia,Null to time-like infinity Green’s functions for asymptotic symmetries in Minkowski spacetime,JHEP11(2015) 160, [arXiv:1509.01408]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[57]
Geometry and Physics of Null Infinity
A. Ashtekar,Geometry and Physics of Null Infinity,arXiv:1409.1800
work page internal anchor Pith review Pith/arXiv arXiv
-
[58]
Field Theories with Conformal Carrollian Symmetry
A. Bagchi, A. Mehra, and P. Nandi,Field Theories with Conformal Carrollian Symmetry, JHEP05(2019) 108, [arXiv:1901.10147]. 32
work page internal anchor Pith review Pith/arXiv arXiv 2019
-
[59]
K. Nguyen and P. West,Carrollian Conformal Fields and Flat Holography,Universe9 (2023), no. 9 385, [arXiv:2305.02884]
-
[60]
G. Barnich, P. Mao, and R. Ruzziconi,BMS current algebra in the context of the Newman–Penrose formalism,Class. Quant. Grav.37(2020), no. 9 095010, [arXiv:1910.14588]
-
[61]
G. Barnich and R. Ruzziconi,Coadjoint representation of the BMS group on celestial Riemann surfaces,JHEP06(2021) 079, [arXiv:2103.11253]
- [62]
-
[63]
Supertranslations call for superrotations
G. Barnich and C. Troessaert,Supertranslations call for superrotations,PoSCNCFG (2010) 010, [arXiv:1102.4632]. [Ann. U. Craiova Phys.21,S11(2011)]
work page internal anchor Pith review Pith/arXiv arXiv 2010
- [64]
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.