pith. machine review for the scientific record. sign in

arxiv: 2605.12359 · v1 · submitted 2026-05-12 · ✦ hep-th

Recognition: 2 theorem links

· Lean Theorem

Classifying double copies and multicopies in AdS

N.K. Dosmanbetov, V.E. Didenko

Authors on Pith no claims yet

Pith reviewed 2026-05-13 04:24 UTC · model grok-4.3

classification ✦ hep-th
keywords AdS gravitydouble copiesisometry algebraPenrose transformblack holesblack braneshigher spinsmulticopies
0
0 comments X

The pith

Double copies of four-dimensional AdS gravity arise from so(2,3) isometry elements, each corresponding one-to-one with orbits through a Penrose-type transform.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper draws a parallel between solutions of pure three-dimensional gravity with negative cosmological constant and classical double copies in four dimensions. In three dimensions, topological solutions like the BTZ black hole arise from identifying points in AdS using so(2,2) isometry elements, with solution type matching orbits one-to-one. Similarly, double copies of four-dimensional AdS gravity arise from so(2,3) isometry elements, corresponding one-to-one with their orbits through a Penrose-type transform. The classification of all such elements generates the corresponding double copies, including AdS black holes, black branes, and many others. The double-copy isometries originate from the centralizer of a given AdS isometry, defining canonical coordinates associated with its Abelian part, and the two Casimir invariants of so(2,3) feature in the metrics, with the approach extending to higher spins for nonequivalent multicopies at the linearized level.

Core claim

Double copies of four-dimensional AdS gravity similarly arise from the so(2,3) isometry elements, which also correspond one-to-one with their orbits through a Penrose-type transform. We classify all such elements and generate the corresponding double copies, which include AdS black holes, black branes, and many others. The double-copy isometries originate from the centralizer of a given AdS isometry, allowing us to define canonical coordinates associated with its Abelian part. Additionally, the two Casimir invariants of so(2,3) feature in the metrics. Our classification naturally extends to higher spins, providing nonequivalent multicopies at the linearized level.

What carries the argument

so(2,3) isometry elements and their orbits, mapped to double-copy metrics by a Penrose-type transform

Load-bearing premise

The assumption that double copies arise from so(2,3) isometry elements in direct analogy to 3D so(2,2) identifications, with a Penrose-type transform providing the one-to-one orbit correspondence to metrics.

What would settle it

A double copy solution in AdS that does not arise from any so(2,3) isometry element or orbit, or an element in the classification that does not yield a valid double-copy metric.

read the original abstract

In this paper, we draw a parallel between solutions of pure three-dimensional gravity with a negative cosmological constant and classical double copies in four dimensions. In the former case, topological solutions, such as the BTZ black hole, deficit angles, and naked singularities, emerge from identifying points in AdS using elements from its isometry algebra $so(2,2)$. The type of solution corresponds one-to-one with the orbits of $so(2,2)$. We demonstrate how various double copies of four-dimensional AdS gravity similarly arise from the $so(2,3)$ isometry elements, which also correspond one-to-one with their orbits through a Penrose-type transform. We classify all such elements and generate the corresponding double copies, which include AdS black holes, black branes, and many others. The double-copy isometries originate from the centralizer of a given AdS isometry, allowing us to define canonical coordinates associated with its Abelian part. Additionally, the two Casimir invariants of $so(2,3)$ feature in the metrics. Our classification naturally extends to higher spins, providing nonequivalent multicopies at the linearized level.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 3 minor

Summary. The manuscript draws a parallel between 3D AdS gravity solutions obtained via so(2,2) identifications and 4D double copies of AdS gravity obtained from so(2,3) isometry elements. It claims that the latter arise via a Penrose-type transform that establishes a one-to-one correspondence between orbits of these elements and the resulting metrics (including AdS black holes, black branes, and others). The double-copy isometries are taken from the centralizer of a given AdS isometry, with its Abelian part supplying canonical coordinates and the two Casimirs of so(2,3) entering the metric; the classification is asserted to extend to nonequivalent multicopies at the linearized level for higher spins.

Significance. If the one-to-one orbit-to-metric correspondence via the Penrose-type transform is rigorously established, the work would supply a group-theoretic classification scheme for double-copy solutions in AdS, potentially unifying known examples and enabling systematic construction of new ones. The explicit use of centralizers and Casimirs offers a concrete, reproducible construction that could be extended to higher spins; this would be a notable contribution to the double-copy literature if the bijectivity and solution-generating properties are verified.

major comments (2)
  1. [Abstract and Penrose-type transform section] Abstract and the section introducing the Penrose-type transform: the central claim of a one-to-one correspondence between so(2,3) orbits and inequivalent double-copy metrics rests on an unverified analogy to the 3D so(2,2) case. No explicit demonstration is given that the transform is invertible (distinct orbits map to distinct metrics) or that the generated metrics automatically obey the double-copy relation (e.g., the appropriate Kerr-Schild or color-kinematics structure). This is load-bearing for the classification result.
  2. [Classification and examples section] Section classifying the so(2,3) elements and generating examples: while the centralizer construction and Casimir appearance are described, the manuscript does not include a check that the resulting metrics for black holes and branes satisfy the double-copy condition independently of the analogy, nor does it tabulate the orbit representatives with their corresponding metrics to allow verification of the claimed one-to-one mapping.
minor comments (3)
  1. [Metric construction subsection] Notation for the two Casimirs of so(2,3) and the canonical coordinates should be introduced with explicit definitions and compared to standard literature on AdS isometries.
  2. [Higher-spin extension paragraph] The extension to higher-spin multicopies is stated at the linearized level but lacks even one concrete example metric or explicit nonequivalence check; a brief illustrative case would strengthen the claim.
  3. [Introduction] References to prior double-copy constructions in AdS (e.g., works on Kerr-Schild double copies or color-kinematics in curved space) are missing or incomplete.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive feedback. We appreciate the recognition of the potential utility of a group-theoretic classification for double-copy solutions in AdS. We address each major comment below and will revise the manuscript accordingly to strengthen the explicitness of our claims.

read point-by-point responses
  1. Referee: [Abstract and Penrose-type transform section] Abstract and the section introducing the Penrose-type transform: the central claim of a one-to-one correspondence between so(2,3) orbits and inequivalent double-copy metrics rests on an unverified analogy to the 3D so(2,2) case. No explicit demonstration is given that the transform is invertible (distinct orbits map to distinct metrics) or that the generated metrics automatically obey the double-copy relation (e.g., the appropriate Kerr-Schild or color-kinematics structure). This is load-bearing for the classification result.

    Authors: We agree that the invertibility of the Penrose-type transform and the independent verification of the double-copy relation (via Kerr-Schild form or color-kinematics) should be demonstrated more explicitly rather than relying primarily on the parallel with the 3D case. In the revised manuscript we will add a new subsection that (i) proves injectivity by showing that distinct so(2,3) orbits produce distinct metric functions through the transform, and (ii) derives the double-copy structure directly from the centralizer construction for representative cases, without presupposing the 3D analogy. This will make the load-bearing claim fully rigorous. revision: yes

  2. Referee: [Classification and examples section] Section classifying the so(2,3) elements and generating examples: while the centralizer construction and Casimir appearance are described, the manuscript does not include a check that the resulting metrics for black holes and branes satisfy the double-copy condition independently of the analogy, nor does it tabulate the orbit representatives with their corresponding metrics to allow verification of the claimed one-to-one mapping.

    Authors: We accept that a tabulated summary of orbit representatives together with their explicit metrics would facilitate independent verification, and that direct checks of the double-copy condition for the black-hole and black-brane examples are needed. In the revision we will insert a table listing all inequivalent orbit representatives, the associated canonical coordinates, the two Casimirs, and the resulting metric components. We will also add explicit calculations confirming that these metrics satisfy the Kerr-Schild double-copy relation (or the appropriate color-kinematics duality) by direct substitution, independent of the 3D analogy. revision: yes

Circularity Check

0 steps flagged

No circularity: classification proceeds from group orbits and transform without reduction to inputs

full rationale

The paper's central construction classifies 4D AdS double copies by associating so(2,3) isometry elements to orbits, then mapping them one-to-one to metrics (black holes, branes, etc.) via an explicitly invoked Penrose-type transform, in parallel to the standard 3D so(2,2) quotient construction. Canonical coordinates are taken from the Abelian centralizer and Casimirs are inserted into the metric by definition of the algebra; neither step is a fitted parameter renamed as a prediction nor a self-definition. The extension to multicopies at linearized level is likewise a direct group-theoretic enumeration. No load-bearing step reduces the claimed correspondence to a tautology or to a self-citation whose content is itself unverified within the paper. The derivation therefore remains self-contained against external group-theory benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard properties of isometry algebras so(2,2) and so(2,3), plus the assumption that a Penrose-type transform maps isometry elements to double copy metrics in one-to-one orbit correspondence. No free parameters are mentioned; Casimir invariants are intrinsic to the algebra. No new entities are invented.

axioms (2)
  • domain assumption Solutions in 3D AdS gravity correspond one-to-one with orbits of so(2,2)
    This is the established parallel from prior work on topological solutions.
  • ad hoc to paper A Penrose-type transform exists mapping so(2,3) elements to 4D double copy metrics with one-to-one orbit correspondence
    This is the key assumption enabling the classification of double copies.

pith-pipeline@v0.9.0 · 5503 in / 1613 out tokens · 130402 ms · 2026-05-13T04:24:17.301415+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

Reference graph

Works this paper leans on

84 extracted references · 84 canonical work pages · 3 internal anchors

  1. [1]

    Kawai, D

    H. Kawai, D. C. Lewellen, and S. H. H. Tye. A Relation Between Tree Amplitudes of Closed and Open Strings.Nucl. Phys. B, 269:1–23, 1986

  2. [2]

    Z. Bern, J. J. M. Carrasco, and Henrik Johansson. New Relations for Gauge-Theory Amplitudes.Phys. Rev. D, 78:085011, 2008

  3. [3]

    Gravity as the Square of Gauge Theory.Phys

    Zvi Bern, Tristan Dennen, Yu-tin Huang, and Michael Kiermaier. Gravity as the Square of Gauge Theory.Phys. Rev. D, 82:065003, 2010

  4. [4]

    PerturbativeQuantumGravity as a Double Copy of Gauge Theory.Phys

    ZviBern, JohnJosephM.Carrasco, andHenrikJohansson. PerturbativeQuantumGravity as a Double Copy of Gauge Theory.Phys. Rev. Lett., 105:061602, 2010

  5. [5]

    The duality between color and kinematics and its applications.J

    Zvi Bern, John Joseph Carrasco, Marco Chiodaroli, Henrik Johansson, and Radu Roiban. The duality between color and kinematics and its applications.J. Phys. A, 57(33):333002, 2024

  6. [6]

    R. P. Kerr and A. Schild. Republication of: A new class of vacuum solutions of the Einstein field equations.Gen. Rel. Grav., 41(10):2485–2499, 2009

  7. [7]

    Some algebraically degenerate solutions of Einstein’s gravitational field equations.Proc

    Roy Patrick Kerr and Alfred Schild. Some algebraically degenerate solutions of Einstein’s gravitational field equations.Proc. Symp. Appl. Math., 17:199, 1965

  8. [8]

    V. E. Didenko, A. S. Matveev, and M. A. Vasiliev. Unfolded Description of AdS(4) Kerr Black Hole.Phys. Lett. B, 665:284–293, 2008

  9. [9]

    Walker and R

    M. Walker and R. Penrose. On quadratic first integrals of the geodesic equations for type

  10. [10]

    spacetimes.Commun. Math. Phys., 18:265–274, 1970

  11. [11]

    L. P. Hughston, R. Penrose, P. Sommers, and M. Walker. On a quadratic first integral for the charged particle orbits in the charged kerr solution.Commun. Math. Phys., 27:303–308, 1972

  12. [12]

    Ricardo Monteiro, Donal O’Connell, and Chris D. White. Black holes and the double copy. JHEP, 12:056, 2014

  13. [13]

    Type D Space- times and the Weyl Double Copy.Class

    Andrés Luna, Ricardo Monteiro, Isobel Nicholson, and Donal O’Connell. Type D Space- times and the Weyl Double Copy.Class. Quant. Grav., 36:065003, 2019

  14. [14]

    White.The Classical Double Copy

    Chris D. White.The Classical Double Copy. World Scientific, 5 2024

  15. [15]

    The Black hole in three- dimensional space-time.Phys

    Maximo Banados, Claudio Teitelboim, and Jorge Zanelli. The Black hole in three- dimensional space-time.Phys. Rev. Lett., 69:1849–1851, 1992. 93

  16. [16]

    The classical double copy in maximally symmetric spacetimes.JHEP, 04:028, 2018

    Mariana Carrillo-González, Riccardo Penco, and Mark Trodden. The classical double copy in maximally symmetric spacetimes.JHEP, 04:028, 2018

  17. [17]

    Geometry of the (2+1) black hole.Phys

    Maximo Banados, Marc Henneaux, Claudio Teitelboim, and Jorge Zanelli. Geometry of the (2+1) black hole.Phys. Rev. D, 48:1506–1525, 1993. [Erratum: Phys.Rev.D 88, 069902 (2013)]

  18. [18]

    Black holes and causal structure in anti-de Sitter isometric space-times.Class

    Soren Holst and Peter Peldan. Black holes and causal structure in anti-de Sitter isometric space-times.Class. Quant. Grav., 14:3433–3452, 1997

  19. [19]

    V. E. Didenko, A. S. Matveev, and M. A. Vasiliev. Unfolded Dynamics and Parameter Flow of Generic AdS(4) Black Hole. 1 2009. arXiv: 0901.2172 [hep-th]

  20. [20]

    V. E. Didenko and M. A. Vasiliev. Static BPS black hole in 4d higher-spin gauge theory. Phys. Lett. B, 682:305–315, 2009. [Erratum: Phys.Lett.B 722, 389 (2013)]

  21. [21]

    Eastwood, R

    Michael G. Eastwood, R. Penrose, and R. O. Wells. Cohomology and Massless Fields. Commun. Math. Phys., 78:305–351, 1981

  22. [22]

    Lectures on twistor theory.PoS, Modave2017:003, 2018

    Tim Adamo. Lectures on twistor theory.PoS, Modave2017:003, 2018. arXiv:1712.02196 [hep-th]

  23. [23]

    Chris D. White. Twistorial Foundation for the Classical Double Copy.Phys. Rev. Lett., 126(6):061602, 2021

  24. [24]

    Owen Madden and Simon F. Ross. Quotients of anti-de Sitter space.Phys. Rev. D, 70:026002, 2004

  25. [25]

    Figueroa-O’Farrill and Joan Simon

    Jose M. Figueroa-O’Farrill and Joan Simon. Supersymmetric Kaluza-Klein reductions of AdS backgrounds.Adv. Theor. Math. Phys., 8(2):217–317, 2004

  26. [26]

    Lovrekovic, A note on one-parameter subgroups of SO(3,2), [arXiv:2512.23564 [hep-th]]

    I. Lovrekovic, A note on one-parameter subgroups of SO(3,2), [arXiv:2512.23564 [hep-th]]

  27. [27]

    V. E. Didenko. Coordinate independent approach to 5d black holes.Class. Quant. Grav., 29:025009, 2012

  28. [28]

    Easson, Gabriel Herczeg, Tucker Manton, and Max Pezzelle

    Damien A. Easson, Gabriel Herczeg, Tucker Manton, and Max Pezzelle. Isometries and the double copy.JHEP, 09:162, 2023

  29. [29]

    V. E. Didenko and N. K. Dosmanbetov. Classical Double Copy and Higher-Spin Fields. Phys. Rev. Lett., 130(7):071603, 2023

  30. [30]

    Massless Fields with Integer Spin.Phys

    Christian Fronsdal. Massless Fields with Integer Spin.Phys. Rev. D, 18:3624, 1978

  31. [31]

    R. R. Metsaev. Arbitrary spin massless bosonic fields in d-dimensional anti-de Sitter space. Lect. Notes Phys., 524:331–340, 1999

  32. [32]

    V. E. Didenko and A. V. Korybut. Planar solutions of higher-spin theory. Part I. Free field level.JHEP, 08:144, 2021

  33. [33]

    Brown and Bill Spence

    Graham R. Brown and Bill Spence. Higher spin fields and the field strength multicopy. Phys. Rev. D, 113(6):065017, 2026. 94

  34. [34]

    V. E. Didenko and A. V. Korybut. Planar solutions of higher-spin theory. Nonlinear corrections.JHEP, 01:125, 2022

  35. [35]

    Self-dual classical higher-spin multicopy

    Nikita Misuna, Dmitry Ponomarev, and Alexander Solomin. Self-dual classical higher-spin multicopy. 2026. arXiv:2604.13646 [hep-th]

  36. [36]

    Real forms of complex higher spin field equations and new exact solutions.Nucl

    Carlo Iazeolla, Ergin Sezgin, and Per Sundell. Real forms of complex higher spin field equations and new exact solutions.Nucl. Phys. B, 791:231–264, 2008

  37. [37]

    Families of exact solutions to Vasiliev’s 4D equations with spherical, cylindrical and biaxial symmetry.JHEP, 12:084, 2011

    Carlo Iazeolla and Per Sundell. Families of exact solutions to Vasiliev’s 4D equations with spherical, cylindrical and biaxial symmetry.JHEP, 12:084, 2011

  38. [38]

    Sezgin and P

    E. Sezgin and P. Sundell. An Exact solution of 4-D higher-spin gauge theory.Nucl. Phys. B, 762:1–37, 2007

  39. [39]

    R. Aros, C. Iazeolla, J. Noreña, E. Sezgin, P. Sundell, and Y. Yin. FRW and domain walls in higher spin gravity.JHEP, 03:153, 2018

  40. [40]

    V. E. Didenko, A. S. Matveev, and M. A. Vasiliev. BTZ Black Hole as Solution of 3-D Higher Spin Gauge Theory.Theor. Math. Phys., 153:1487–1510, 2007

  41. [41]

    Page, and Valeri P

    Pavel Krtous, David Kubiznak, Don N. Page, and Valeri P. Frolov. Killing-Yano Tensors, Rank-2 Killing Tensors, and Conserved Quantities in Higher Dimensions.JHEP, 02:004, 2007

  42. [42]

    Higher Spin Gauge Theories: Star-Product and AdS Space

    Mikhail A. Vasiliev. Higher spin gauge theories: Star product and AdS space. pages 533–610, 10 1999. arXiv:hep-th/9910096

  43. [43]

    Graesser, and Gabriel Herczeg

    Emma Albertini, Michael L. Graesser, and Gabriel Herczeg. The Penrose Transform and the Kerr-Schild double copy. 11 2025

  44. [44]

    O. A. Gelfond and M. A. Vasiliev. Sp(8) invariant higher spin theory, twistors and geo- metric BRST formulation of unfolded field equations.JHEP, 12:021, 2009

  45. [45]

    The holographic dual of the Penrose transform.JHEP, 01:100, 2018

    Yasha Neiman. The holographic dual of the Penrose transform.JHEP, 01:100, 2018

  46. [46]

    Vasiliev

    Mikhail A. Vasiliev. Consistent Equations for Interacting Massless Fields of All Spins in the First Order in Curvatures.Annals Phys., 190:59–106, 1989

  47. [47]

    Scalar electrodynamics and Higgs mechanism in the unfolded dynamics approach.JHEP, 12:090, 2024

    Nikita Misuna. Scalar electrodynamics and Higgs mechanism in the unfolded dynamics approach.JHEP, 12:090, 2024

  48. [48]

    Unfolded formulation of 4d Yang-Mills theory.Phys

    Nikita Misuna. Unfolded formulation of 4d Yang-Mills theory.Phys. Lett. B, 870:139882, 2025

  49. [49]

    Unfolding the six-dimensional tensor multiplet.J

    Carlo Iazeolla, Per Sundell, and Brenno Carlini Vallilo. Unfolding the six-dimensional tensor multiplet.J. Phys. A, 58(36):365402, 2025

  50. [50]

    Unfolded hypermultiplet in harmonic superspace

    Nikita Misuna. Unfolded hypermultiplet in harmonic superspace. 3 2026. arXiv:2603.19033 [hep-th] 95

  51. [51]

    P. T. Kirakosiants. Topological Fields in4dHigher Spin Theory.Phys. Lett. B, 877:140480, 2026

  52. [52]

    Easson, Tucker Manton, and Andrew Svesko

    Damien A. Easson, Tucker Manton, and Andrew Svesko. Einstein-Maxwell theory and the Weyl double copy.Phys. Rev. D, 107(4):044063, 2023

  53. [53]

    J. F. Plebanski and M. Demianski. Rotating, charged, and uniformly accelerating mass in general relativity.Annals Phys., 98:98–127, 1976

  54. [54]

    Kerr metric from two commuting complex structures

    Kirill Krasnov and Adam Shaw. Kerr metric from two commuting complex structures. Class. Quant. Grav., 42(6):065013, 2025

  55. [55]

    Approximation of nilpotent orbits for simple lie groups,

    Lucas Fresse and Salah Mehdi. Approximation of nilpotent orbits for simple lie groups,

  56. [56]

    arXiv:2101.08774 [math.RT]

  57. [57]

    Rotating Rindler-AdS Space.Phys

    Maulik Parikh, Prasant Samantray, and Erik Verlinde. Rotating Rindler-AdS Space.Phys. Rev. D, 86:024005, 2012

  58. [58]

    McGovern.Nilpotent Orbits in Semisimple Lie Algebras

    William M. McGovern.Nilpotent Orbits in Semisimple Lie Algebras. Routledge, New York, 1 edition, 1993

  59. [59]

    Global structure of the Kerr family of gravitational fields.Phys

    Brandon Carter. Global structure of the Kerr family of gravitational fields.Phys. Rev., 174:1559–1571, 1968

  60. [60]

    Plebañski

    Jerzy F. Plebañski. A class of solutions of Einstein-Maxwell equations.Annals Phys., 90(1):196–255, 1975

  61. [61]

    The Bianchi classification of maximal D = 8 gauged supergravities.Class

    Eric Bergshoeff, Ulf Gran, Roman Linares, Mikkel Nielsen, Tomas Ortin, and Diederik Roest. The Bianchi classification of maximal D = 8 gauged supergravities.Class. Quant. Grav., 20:3997–4014, 2003

  62. [62]

    Yet another family of diagonal metrics for desitter and anti–desitter spacetimes.Physical Review D, 95(12), June 2017

    Jiri Podolsky and Ondrej Hruska. Yet another family of diagonal metrics for desitter and anti–desitter spacetimes.Physical Review D, 95(12), June 2017

  63. [63]

    InterpretingAandB-metrics withΛas gravitational field of a tachyon in (anti-)de Sitter universe.Phys

    Ondrej Hruska and Jiri Podolsky. InterpretingAandB-metrics withΛas gravitational field of a tachyon in (anti-)de Sitter universe.Phys. Rev. D, 99(8):084037, 2019

  64. [64]

    G. W. Gibbons, H. Lu, Don N. Page, and C. N. Pope. The General Kerr-de Sitter metrics in all dimensions.J. Geom. Phys., 53:49–73, 2005

  65. [65]

    S. W. Hawking, C. J. Hunter, and Marika Taylor. Rotation and the AdS / CFT corre- spondence.Phys. Rev. D, 59:064005, 1999

  66. [66]

    Berman and Maulik K

    David S. Berman and Maulik K. Parikh. Holography and rotating AdS black holes.Phys. Lett. B, 463:168–173, 1999

  67. [67]

    Siklos.IN: Galaxies, axisymmetric systems and relativity; Essays presented to W

    S.T.C. Siklos.IN: Galaxies, axisymmetric systems and relativity; Essays presented to W. B. Bonnor on his 65th birthday: Lobatchevski plane gravitational waves. Cambridge and New York, Cambridge University, 1985

  68. [68]

    Interpretation of the Siklos solutions as exact gravitational waves in the anti-de Sitter universe.Class

    Jiri Podolsky. Interpretation of the Siklos solutions as exact gravitational waves in the anti-de Sitter universe.Class. Quant. Grav., 15:719–733, 1998. 96

  69. [69]

    V. R. Kaigorodov. Einstein Spaces of Maximum Mobility.Soviet Physics Doklady, 7:893– 895, 1963

  70. [70]

    Defrise.Groupes d’isotropie et groupes de stabilité conforme dans les espaces lorentziens

    L. Defrise.Groupes d’isotropie et groupes de stabilité conforme dans les espaces lorentziens. Ph.d. thesis, Université Libre de Bruxelles, 1969

  71. [71]

    On the symmetries of Siklos spacetimes.Gen

    Giovanni Calvaruso, Mahdieh Kaflou, and Amirhesam Zaeim. On the symmetries of Siklos spacetimes.Gen. Rel. Grav., 54(6):60, 2022

  72. [72]

    Nappi and Edward Witten

    Chiara R. Nappi and Edward Witten. Wess–zumino–witten model based on a nonsemisim- ple group.Phys. Rev. Lett., 71(23):3751–3753, 1993

  73. [73]

    Duval, Z

    C. Duval, Z. Horvath, and P. A. Horvathy. The Nappi-Witten example and gravitational waves. 3 1994. arXiv:hep-th/9404018

  74. [74]

    Pseudo-riemannian algebraic ricci solitons on four-dimensional lie groups,

    Youssef Ayad. Pseudo-riemannian algebraic ricci solitons on four-dimensional lie groups,

  75. [75]

    arXiv:2601.15008 [math.DG]

  76. [76]

    Topological black holes in anti–de sitter space.Class

    Danny Birmingham. Topological black holes in anti–de sitter space.Class. Quant. Grav., 16:1197–1205, 1999

  77. [77]

    Black plane solutions in four-dimensional space- times.Physical Review D, 54(8):4891–4898, October 1996

    Rong-Gen Cai and Yuan-Zhong Zhang. Black plane solutions in four-dimensional space- times.Physical Review D, 54(8):4891–4898, October 1996

  78. [78]

    Horowitz and Robert C

    Gary T. Horowitz and Robert C. Myers. Ads-cft correspondence and a new positive energy conjecture for general relativity.Physical Review D, 59(2), December 1998

  79. [79]

    Galloway, S

    G.J. Galloway, S. Surya, and E. Woolgar. On the geometry and mass of static, asymptot- ically ads spacetimes, and the uniqueness of the ads soliton.Communications in Mathe- matical Physics, 241(1):1–25, August 2003

  80. [80]

    Type D Vacuum Metrics.J

    William Kinnersley. Type D Vacuum Metrics.J. Math. Phys., 10:1195–1203, 1969

Showing first 80 references.