REVIEW 1 major objections 5 minor 5 cited by
Rotating Topological Stars
T0 review · 1 major / 5 minor · reviewed 2026-08-16 · deepseek-v4-flash
Pith's one-line read Rotating Topological Stars are smooth, horizonless, ergoregion-free five-dimensional solitons obtained by analytic continuation of known rotating black string solutions, with separable geodesic and scalar perturbation equations.
desk verdict A credible first rotating generalization of topological stars, with a real but likely fixable gap in the no-CTC proof. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
The authors start with a known three-parameter family of rotating black-string solutions in five-dimensional supergravity, then analytically continue one parameter so that the square of the rotation becomes negative. In this new branch, the singularity is replaced by a smooth cap where the geometry ends. To make the cap perfectly regular, the angular momentum must be quantized, and the space at infinity becomes a finite quotient of flat space. They then verify that the time Killing vector is everywhere timelike, so no ergoregion exists, and argue that closed timelike curves are absent.
Finally, they show that particles moving on geodesics have a hidden conserved quantity, making the motion integrable, and that scalar waves separate into two ordinary differential equations of confluent Heun type, the same family of equations that appears in Kerr perturbation theory. This opens the door to computing quasinormal modes and echoes that could, in principle, distinguish these objects from black holes in gravitational-wave data.
Extended reading notes
Core claim
Quote from the abstract: "We show that for specific choices of the parameters and quantized values of the angular momentum the geometry terminates on a smooth five-dimensional cap, and it displays neither ergoregion nor closed timelike curves." If true, there exists a three-parameter family of smooth, horizonless rotating solutions of minimal 5D supergravity that interpolate between Kerr and static Topological Stars, with integrable geodesic motion and scalar perturbations separating into confluent Heun equations.
Load-bearing premise
The proof of absence of closed timelike curves in Section 3.3 (after eq. (3.50)) relies on the assertion that the unshown functions D^(0)(r), D^(1)(r), G^(0)(r), G^(1)(r), G^(2)(r) are everywhere positive except at the fixed points of the isometry B_yhat. The explicit forms are not displayed, so the reader cannot verify the positivity claim that underpins the 'no CTC' conclusion. If any of these functions changed sign inside the geometry, closed timelike curves could appear and the central claim would fail.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper constructs 'Rotating Topological Stars' (RTS) as a three-parameter family of solutions of five-dimensional minimal supergravity with Chern-Simons term, obtained by analytic continuation of the Compere-de Buyl-Jamsin-Virmani rotating black string to the branch a^2<0. In the regime r_b>r_s, and upon imposing the smooth-cap condition R_y=γ and the angular-momentum quantization (3.41), the solution is claimed to be horizonless, free of ergoregions and closed timelike curves, and to end on a smooth cap of topology R×S^2 while asymptoting to (R^{1,3}×S^1)/Z_q. The paper also computes five- and four-dimensional charges, discusses M-theory and type IIB embeddings in terms of brane intersections, proves separability of geodesic motion and of massless scalar perturbations, and connects the resulting confluent Heun equations to Seiberg-Witten curves.
Significance. If the unproved positivity assertion in Sec. 3.3 is confirmed, the paper delivers an explicit, horizonless, rotating soliton family in a minimal supergravity theory, continuously connected to Kerr (at r_b=0) and to the static topological star (at a=0), with integrable geodesic motion and separable scalar perturbations. This is a valuable step for the fuzzball/ECO program because the explicit metric makes concrete gravitational-wave phenomenology possible. Strengths of the presentation include the use of an independently constructed metric from [28] (so the smoothness and quantization conditions are derived rather than fitted), explicit analytic computations of charges and conserved quantities, and falsifiable predictions such as the absence of an ergoregion and the small-rotation light-ring behavior. The central no-CTC claim, however, currently rests on an unverified symbolic assertion, so the manuscript is not yet self-contained.
major comments (1)
- [Sec. 3.3, Eqs. (3.49)-(3.50)] The proof of absence of closed timelike curves is incomplete. The positivity of D and g_haty_haty is reduced to the assertion that the five functions D^(0), D^(1), G^(0), G^(1), G^(2) are positive except at the fixed points of B_haty, but their explicit expressions are not displayed and no proof is supplied. Since a sign change in any of these functions inside r≥r_+, |χ|<1 would make the determinant or g_haty_haty negative and would create CTCs, this is a load-bearing gap in the abstract's central claim. Please provide the explicit rational forms, in an appendix if necessary, together with a verification of positivity over the full domain of parameters and coordinates; as the functions are rational in r and χ, this is a finite check that can be documented.
minor comments (5)
- [Eq. (3.46)] The inequality chain is not valid as written: from r≥r_+>r_b and 0<ξ_t<1 one cannot conclude ((1-ξ_t^2)r-r_b)/r>0, since r_+ may be smaller than r_b/(1-ξ_t^2); for example r_s=0.9, r_b=1, r_+=1.1 gives a negative value at r=r_+. The no-ergoregion conclusion nevertheless follows immediately from (3.45), where rb>rs makes all displayed terms nonnegative, so the faulty intermediate step should be corrected or deleted.
- [Sec. 3.1 and Eq. (3.30)] The phase-diagram paragraph refers to 'section ??' for a detailed discussion, and the text after Eq. (3.30) contains an unresolved '[?]' citation; both should be completed.
- [Fig. 1 caption] The caption uses t1 and t2 without defining these quantities in the text, so the reader cannot tell which projected line corresponds to which phase.
- [Sec. 4, Eq. (4.33)] The exact light-ring condition for general rotation is stated to be a quintic, but the small-a expansion (4.34) is carried only to first order; the text should state explicitly that existence and uniqueness of light rings for arbitrary a is left open.
- [Abstract] The phrase 'smooth five-dimensional cap' could be misread: the cap itself has topology R×S^2 and is a three-dimensional locus at which the y-circle shrinks; consider rephrasing to 'the five-dimensional geometry ends on a smooth cap'.
Assumptions & free parameters
assumptions (5)
- domain assumption The known G2-dual solution of Compere et al. (Eq. 3.4) solves the minimal 5D supergravity action (3.1).
- domain assumption Analytic continuation to imaginary a^2 preserves the field equations and yields a real Lorentzian metric via the symmetry (3.6).
- ad hoc to paper All undisplayed functions D^(0), D^(1), G^(0), G^(1), G^(2) in eqs. (3.49)-(3.50) are positive except at fixed points of B_yhat.
- domain assumption The asymptotic orbifold (R^{1,3} x S^1)/Z_q with the stated action (3.38) is an admissible boundary condition.
- domain assumption Equal-charge identification Q1=Q2=Q3 in brane systems gives the static TS limit and the stringy embeddings.
Cite this review
Pith. "Pith review of Rotating Topological Stars." pith.science (2026). https://pith.science/paper/HWUFRGHW
@misc{pith2026250412235,
author = {Pith},
title = {Pith review of: Rotating Topological Stars},
year = {2026},
howpublished = {\url{https://pith.science/paper/HWUFRGHW}},
note = {Machine review of arXiv:2504.12235}
}
read the original abstract
We construct a three-parameter family of smooth and horizonless rotating solutions of Einstein-Maxwell theory with Chern-Simons term in five dimensions and discuss their stringy origin in terms of three-charge brane systems in Type IIB and M-theory. The general solution interpolates smoothly between Kerr and static Topological Star geometries. We show that for specific choices of the parameters and quantized values of the angular momentum the geometry terminates on a smooth five-dimensional cap, and it displays neither ergoregion nor closed timelike curves. We discuss the propagation of particles and waves showing that geodetic motion is integrable and the radial and angular propagation of scalar perturbations can be separated and described in terms of two ordinary differential equations of confluent Heun type.
Forward citations
Cited by 5 Pith papers
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5d Schwarzschild-Tangherlini spacetime: MST-like formalism for a Reduced Confluent Heun Equation
An original MST-like formalism is constructed for the reduced confluent Heun radial equation of 5D Schwarzschild-Tangherlini scalars, validated by matching the renormalized angular momentum to the quantum Seiberg-Witt...
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"Waveforms" at the Horizon
A probe scattering off a Schwarzschild black hole transfers a definite leading-order post-Minkowskian angular momentum to the horizon, given by new closed formulas (3.24b), (3.29), (3.36).
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Characterizing geodesic deviations in a Topological Star spacetime: massive, charged, spinning and stringy-like objects
Nearby geodesics, spinning particles, magnetically charged particles and string probes all deviate from geodesic motion in a topological star, reducing to Schwarzschild plus small alpha-dependent corrections.
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Probing the multipolar structure of Myers-Perry black holes with scattering amplitudes
A Kerr-Schild gauge computation gives analytic scattering amplitudes and eikonal phases for Myers-Perry black holes, exposing spin-induced stress multipoles that have no four-dimensional counterpart.
-
Extreme mass ratio inspirals around topological stars
A scalar charge orbiting a topological star produces fluxes that deviate from the black hole case and can dephase by up to 10^4 radians over a year, while QNM resonances are too narrow to be observable.
Reference graph
Works this paper leans on
-
[28]
G. Compere, S. de Buyl, E. Jamsin and A. Virmani, G2 Dualities in D=5 Supergravity and Black Strings, Class. Quant. Grav. 26 (2009) 125016 [ 0903.1645]
arXiv 2009
-
[1]
Mathur, The Fuzzball proposal for black holes: An Elementary review , Fortsch
S.D. Mathur, The Fuzzball proposal for black holes: An Elementary review , Fortsch. Phys. 53 (2005) 793 [ hep-th/0502050]
arXiv 2005
-
[2]
A. Einstein and W. Pauli, On the Non-Existence of Regular Stationary Solutions of Relativistic Field Equations , Annals Math. 44 (1943) 131
work page 1943
-
[3]
S. Giusto, S.D. Mathur and A. Saxena, Dual geometries for a set of 3-charge microstates , Nucl. Phys. B 701 (2004) 357 [ hep-th/0405017]
arXiv 2004
-
[4]
S. Giusto, S.D. Mathur and A. Saxena, 3-charge geometries and their CFT duals , Nucl. Phys. B 710 (2005) 425 [ hep-th/0406103]
arXiv 2005
-
[5]
I. Bena and N.P. Warner, Bubbling supertubes and foaming black holes , Phys. Rev. D 74 (2006) 066001 [ hep-th/0505166]
arXiv 2006
-
[6]
I. Bena and N.P. Warner, Black holes, black rings and their microstates , Lect. Notes Phys. 755 (2008) 1 [ hep-th/0701216]
arXiv 2008
-
[7]
I. Bena, S. Giusto, R. Russo, M. Shigemori and N.P. Warner, Habemus Superstratum! A constructive proof of the existence of superstrata , JHEP 05 (2015) 110 [ 1503.01463]
arXiv 2015
Show all 62 references
-
[8]
I. Bah, I. Bena, P. Heidmann, Y. Li and D.R. Mayerson, Gravitational footprints of black holes and their microstate geometries , JHEP 10 (2021) 138 [ 2104.10686]
2021 arXiv
-
[9]
Bah and P
I. Bah and P. Heidmann, Topological Stars and Black Holes , Phys. Rev. Lett. 126 (2021) 151101 [2011.08851]
2021 arXiv
-
[10]
Bah and P
I. Bah and P. Heidmann, Topological stars, black holes and generalized charged Weyl solutions, JHEP 09 (2021) 147 [ 2012.13407]
2021 arXiv
-
[11]
I. Bah, P. Heidmann and P. Weck, Schwarzschild-like topological solitons, JHEP 08 (2022) 269 [2203.12625]
2022 arXiv
-
[12]
Chakraborty and P
S. Chakraborty and P. Heidmann, Microstates of Non-extremal Black Holes: A New Hope , 2503.13589
-
[13]
Heidmann, I
P. Heidmann, I. Bah and E. Berti, Imaging topological solitons: The microstructure behind the shadow, Phys. Rev. D 107 (2023) 084042 [ 2212.06837]
2023 arXiv
-
[14]
Bianchi, G
M. Bianchi, G. Di Russo, A. Grillo, J.F. Morales and G. Sudano, On the stability and deformability of top stars , JHEP 12 (2023) 121 [ 2305.15105]
2023 arXiv
-
[15]
Heidmann, N
P. Heidmann, N. Speeney, E. Berti and I. Bah, Cavity effect in the quasinormal mode spectrum of topological stars, Phys. Rev. D 108 (2023) 024021 [ 2305.14412]
2023 arXiv
-
[16]
I. Bena, G. Di Russo, J.F. Morales and A. Ruip´ erez, Non-spinning tops are stable , JHEP 10 (2024) 071 [ 2406.19330]
2024 arXiv
-
[17]
Melis, F
M. Melis, F. Corelli, R. Croft and P. Pani, Black hole spectroscopy and nonlinear echoes in Einstein-Maxwell-scalar theory, Phys. Rev. D 111 (2025) 064072 [ 2412.14259]
2025 arXiv
-
[18]
A. Dima, M. Melis and P. Pani, Nonradial stability of topological stars , 2502.04444
-
[19]
Bianchi, D
M. Bianchi, D. Bini and G. Di Russo, Scalar perturbations of topological-star spacetimes, Phys. Rev. D 110 (2024) 084077 [ 2407.10868]
2024 arXiv
-
[20]
Bianchi, D
M. Bianchi, D. Bini and G. Di Russo, Scalar waves in a topological star spacetime: Self-force and radiative losses , Phys. Rev. D 111 (2025) 044017 [ 2411.19612]. – 27 –
2025 arXiv
-
[21]
Di Russo, M
G. Di Russo, M. Bianchi and D. Bini, Scalar waves from unbound orbits in a TS spacetime: PN reconstruction of the field and radiation losses in a self-force approach , 2502.21040
-
[22]
Bianchi, D
M. Bianchi, D. Consoli, A. Grillo, J.F. Morales, P. Pani and G. Raposo, Distinguishing fuzzballs from black holes through their multipolar structure , Phys. Rev. Lett. 125 (2020) 221601 [2007.01743]
2020 arXiv
-
[23]
Bena and D.R
I. Bena and D.R. Mayerson, Multipole Ratios: A New Window into Black Holes , Phys. Rev. Lett. 125 (2020) 221602 [ 2006.10750]
2020 arXiv
-
[24]
Bianchi, D
M. Bianchi, D. Consoli, A. Grillo, J.F. Morales, P. Pani and G. Raposo, The multipolar structure of fuzzballs , JHEP 01 (2021) 003 [ 2008.01445]
2021 arXiv
-
[25]
Bena and D.R
I. Bena and D.R. Mayerson, Black Holes Lessons from Multipole Ratios , JHEP 03 (2021) 114 [2007.09152]
2021 arXiv
-
[26]
Ikeda, M
T. Ikeda, M. Bianchi, D. Consoli, A. Grillo, J.F. Morales, P. Pani et al., Black-hole microstate spectroscopy: Ringdown, quasinormal modes, and echoes , Phys. Rev. D 104 (2021) 066021 [ 2103.10960]
2021 arXiv
-
[27]
Staelens, D.R
S. Staelens, D.R. Mayerson, F. Bacchini, B. Ripperda and L. K¨ uchler, Black hole photon rings beyond general relativity , Phys. Rev. D 107 (2023) 124026 [ 2303.02111]
2023 arXiv
-
[29]
Horowitz and A
G.T. Horowitz and A. Strominger, Black strings and P-branes , Nucl. Phys. B 360 (1991) 197
1991
-
[30]
Sierra, N=2 MAXWELL MATTER EINSTEIN SUPERGRAVITIES IN D = 5, D = 4 AND D = 3 , Phys
G. Sierra, N=2 MAXWELL MATTER EINSTEIN SUPERGRAVITIES IN D = 5, D = 4 AND D = 3 , Phys. Lett. B 157 (1985) 379
1985
-
[31]
Gueven, Black p-brane solutions of D = 11 supergravity theory , Phys
R. Gueven, Black p-brane solutions of D = 11 supergravity theory , Phys. Lett. B 276 (1992) 49
1992
-
[32]
Ortin, Gravity and Strings , Cambridge Monographs on Mathematical Physics, Cambridge University Press, 2nd ed
T. Ortin, Gravity and Strings , Cambridge Monographs on Mathematical Physics, Cambridge University Press, 2nd ed. ed. (7, 2015), 10.1017/CBO9781139019750
2015 doi
-
[33]
Gunaydin, G
M. Gunaydin, G. Sierra and P.K. Townsend, The Geometry of N=2 Maxwell-Einstein Supergravity and Jordan Algebras, Nucl. Phys. B 242 (1984) 244
1984
-
[34]
Gibbons and S.W
G.W. Gibbons and S.W. Hawking, Classification of Gravitational Instanton Symmetries , Commun. Math. Phys. 66 (1979) 291
1979
-
[35]
Friedman, Ergosphere instability, Commun
J.L. Friedman, Ergosphere instability, Commun. Math. Phys. 63 (1978) 243
1978
-
[36]
Cardoso, O.J.C
V. Cardoso, O.J.C. Dias, J.L. Hovdebo and R.C. Myers, Instability of non-supersymmetric smooth geometries, Phys. Rev. D 73 (2006) 064031 [ hep-th/0512277]
2006 arXiv
-
[37]
Gibbons and N.P
G.W. Gibbons and N.P. Warner, Global structure of five-dimensional fuzzballs , Class. Quant. Grav. 31 (2014) 025016 [ 1305.0957]
2014 arXiv
-
[38]
Eperon, H.S
F.C. Eperon, H.S. Reall and J.E. Santos, Instability of supersymmetric microstate geometries, JHEP 10 (2016) 031 [ 1607.06828]
2016 arXiv
-
[39]
Jejjala, O
V. Jejjala, O. Madden, S.F. Ross and G. Titchener, Non-supersymmetric smooth geometries and D1-D5-P bound states , Phys. Rev. D 71 (2005) 124030 [ hep-th/0504181]
2005 arXiv
-
[40]
Bianchi, C
M. Bianchi, C. Di Benedetto, G. Di Russo and G. Sudano, Charge instability of JMaRT geometries, JHEP 09 (2023) 078 [ 2305.00865]. – 28 –
2023 arXiv
-
[41]
Elvang, R
H. Elvang, R. Emparan, D. Mateos and H.S. Reall, Supersymmetric black rings and three-charge supertubes, Phys. Rev. D 71 (2005) 024033 [ hep-th/0408120]
2005 arXiv
-
[42]
Gregory and R
R. Gregory and R. Laflamme, Black strings and p-branes are unstable , Phys. Rev. Lett. 70 (1993) 2837 [ hep-th/9301052]
1993 arXiv
-
[43]
Miyamoto, Analytic evidence for the Gubser-Mitra conjecture , Phys
U. Miyamoto, Analytic evidence for the Gubser-Mitra conjecture , Phys. Lett. B 659 (2008) 380 [0709.1028]
2008 arXiv
-
[44]
Aminov, A
G. Aminov, A. Grassi and Y. Hatsuda, Black Hole Quasinormal Modes and Seiberg–Witten Theory, Annales Henri Poincare 23 (2022) 1951 [ 2006.06111]
2022 arXiv
-
[45]
Bianchi, D
M. Bianchi, D. Consoli, A. Grillo and J.F. Morales, QNMs of branes, BHs and fuzzballs from quantum SW geometries , Phys. Lett. B 824 (2022) 136837 [ 2105.04245]
2022 arXiv
-
[46]
Bianchi, D
M. Bianchi, D. Consoli, A. Grillo and J.F. Morales, More on the SW-QNM correspondence , JHEP 01 (2022) 024 [ 2109.09804]
2022 arXiv
-
[47]
Bonelli, C
G. Bonelli, C. Iossa, D. Panea Lichtig and A. Tanzini, Exact solution of Kerr black hole perturbations via CFT2 and instanton counting: Greybody factor, quasinormal modes, and Love numbers, Phys. Rev. D 105 (2022) 044047 [ 2105.04483]
2022 arXiv
-
[48]
Bonelli, C
G. Bonelli, C. Iossa, D. Panea Lichtig and A. Tanzini, Irregular Liouville Correlators and Connection Formulae for Heun Functions , Commun. Math. Phys. 397 (2023) 635 [2201.04491]
2023 arXiv
-
[49]
Bianchi and G
M. Bianchi and G. Di Russo, 2-charge circular fuzz-balls and their perturbations , 2212.07504
-
[50]
Consoli, F
D. Consoli, F. Fucito, J.F. Morales and R. Poghossian, CFT description of BH’s and ECO’s: QNMs, superradiance, echoes and tidal responses , JHEP 12 (2022) 115 [ 2206.09437]
2022 arXiv
-
[51]
Bautista, G
Y.F. Bautista, G. Bonelli, C. Iossa, A. Tanzini and Z. Zhou, Black Hole Perturbation Theory Meets CFT2: Kerr Compton Amplitudes from Nekrasov-Shatashvili Functions , 2312.05965
-
[52]
Bianchi, G
M. Bianchi, G. Dibitetto and J.F. Morales, Gauge theory meets cosmology, 2408.03243
-
[53]
Di Russo, F
G. Di Russo, F. Fucito and J.F. Morales, Tidal resonances for fuzzballs , 2402.06621
-
[54]
Cipriani, G
A. Cipriani, G. Di Russo, F. Fucito, J.F. Morales, H. Poghosyan and R. Poghossian, Resumming Post-Minkowskian and Post-Newtonian gravitational waveform expansions , 2501.19257
-
[55]
Dowker, J.P
F. Dowker, J.P. Gauntlett, G.W. Gibbons and G.T. Horowitz, The Decay of magnetic fields in Kaluza-Klein theory , Phys. Rev. D 52 (1995) 6929 [ hep-th/9507143]
1995 arXiv
-
[56]
Bianchi, D
M. Bianchi, D. Consoli and J.F. Morales, Probing Fuzzballs with Particles, Waves and Strings, JHEP 06 (2018) 157 [ 1711.10287]
2018 arXiv
-
[57]
Bianchi, D
M. Bianchi, D. Consoli, A. Grillo and J.F. Morales, The dark side of fuzzball geometries , JHEP 05 (2019) 126 [ 1811.02397]
2019 arXiv
-
[58]
Bianchi, A
M. Bianchi, A. Grillo and J.F. Morales, Chaos at the rim of black hole and fuzzball shadows , JHEP 05 (2020) 078 [ 2002.05574]
2020 arXiv
-
[59]
Bacchini, D.R
F. Bacchini, D.R. Mayerson, B. Ripperda, J. Davelaar, H. Olivares, T. Hertog et al., Fuzzball Shadows: Emergent Horizons from Microstructure , Phys. Rev. Lett. 127 (2021) 171601 [2103.12075]
2021 arXiv
-
[60]
Cipriani, A
A. Cipriani, A. De Santis, G. Di Russo, A. Grillo and L. Tabarroni, Hamiltonian Neural Networks approach to fuzzball geodesics , 2502.20881. – 29 –
-
[61]
Cipriani, C
A. Cipriani, C. Di Benedetto, G. Di Russo, A. Grillo and G. Sudano, Charge (in)stability and superradiance of Topological Stars, JHEP 07 (2024) 143 [ 2405.06566]
2024 arXiv
-
[62]
A. Dima, M. Melis and P. Pani, Spectroscopy of magnetized black holes and topological stars , 2406.19327. – 30 –
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