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arxiv: 2606.30426 · v1 · pith:FS3QQVQCnew · submitted 2026-06-29 · 🌀 gr-qc

Comment on the "New Rotating Black Hole in Electromagnetic Fields: Cosmological Horizon without Cosmological Constant''

Hryhorii Ovcharenko This is my paper

Pith reviewed 2026-06-30 04:53 UTC · model grok-4.3

classification 🌀 gr-qc
keywords black holesKundt spacetimeselectrovacuum solutionstype D spacetimescoordinate transformationsgeneral relativityaccelerating chargesrotating solutions
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0 comments X

The pith

The claimed new rotating black hole spacetime matches known electrovacuum Kundt solutions of type D with charge.

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

This comment establishes that the background metric presented as novel is already contained in the class of electrovacuum Kundt spacetimes of algebraic type D carrying electric or magnetic charge. The demonstration proceeds by first determining the algebraic type of the curvature and then exhibiting explicit coordinate transformations that recover the standard form of the accelerating charged solution. A sympathetic reader cares because the identification places the rotating black hole inside an existing family rather than outside it, clarifying how Kerr-like solutions sit in backgrounds generated by accelerating charges.

Core claim

The background spacetime is an electrovacuum Kundt spacetime of type D with either electric or magnetic charge. This membership is shown by algebraic classification of the Weyl tensor followed by construction of coordinate transformations that map the metric exactly onto the known accelerating-charge family.

What carries the argument

Algebraic classification as type D Kundt electrovacuum spacetime together with the explicit coordinate transformation to the accelerating-charge family.

If this is right

  • The general solution belongs to the established family of electrovacuum Kundt spacetimes of type D.
  • Kerr-like black holes can be embedded in backgrounds produced by an accelerating electric or magnetic charge.
  • No independent cosmological horizon arises outside the acceleration parameter already present in the mapped solution.
  • Further members of the class inherit known properties of Kundt type D metrics.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Stability or geodesic results already derived for Kundt type D electrovacuum metrics apply directly to this background.
  • Similar claims of new rotating solutions in electromagnetic fields should first test membership in the Kundt type D charged family.
  • The reported cosmological horizon may be re-expressed as an acceleration horizon once the coordinate map is used.

Load-bearing premise

Both the algebraic classification of the spacetime as type D Kundt and the existence of a complete coordinate transformation onto the known accelerating-charge family must hold without gaps.

What would settle it

A calculation showing that the curvature invariants or Weyl scalars remain inequivalent to those of any member of the known Kundt type D electrovacuum family after exhaustive coordinate redefinitions.

read the original abstract

In this comment we discuss some properties of the novel spacetime, recently found in [L. Ma, H. L\"{u}, arXiv:2606.23782]. In particular, we draw attention to the background of this solution that the authors claim to be a new spacetime. We show that this is not the case because this background belongs to the special class of electrovacuum Kundt spacetimes of type D with either electric or magnetic charge. We show this by first analyzing the algebraic properties of this spacetime, and then by finding the explicit coordinate transformations. We hope that this analysis of the background allows for a better understanding of the structure of the general class of this type, namely as the Kerr-like black holes in the background generated by an accelerating electric or magnetic charge.

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

0 major / 1 minor

Summary. This comment paper examines the background metric of the rotating black hole solution proposed in Ma & Lü (arXiv:2606.23782). It claims that this background is not a new spacetime but belongs to the known class of electrovacuum Kundt spacetimes of Petrov type D carrying either electric or magnetic charge. The argument proceeds in two steps: (i) algebraic classification via the Weyl and Ricci scalars to establish the type-D Kundt property, and (ii) explicit coordinate transformations that map the metric onto the standard accelerating-charge family.

Significance. If the classification and coordinate mappings hold, the result correctly situates the solution inside an established family of exact electrovacuum solutions, thereby preventing an erroneous claim of novelty and clarifying the geometric structure for subsequent physical analysis.

minor comments (1)
  1. The abstract refers to 'the background of this solution'; a brief sentence in §1 or §2 clarifying which exact line element from Ma & Lü is under discussion would help readers locate the relevant equations without consulting the original paper.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of our comment and for recommending acceptance. Their summary correctly identifies the two main elements of our analysis: the algebraic classification establishing the electrovacuum Kundt type-D character and the explicit coordinate transformations that recover the standard accelerating-charge family.

Circularity Check

0 steps flagged

No significant circularity; identification via explicit classification and coordinate change

full rationale

The paper establishes its claim by first computing the Weyl and Ricci scalars to fix the algebraic type as D and the Kundt property, then exhibiting an explicit coordinate transformation mapping the metric onto the known accelerating-charge family. Both steps are standard, independent GR operations that do not reduce to self-definitions, fitted inputs, or self-citation chains; they are falsifiable against external exact solutions in the literature. No load-bearing premise relies on prior work by the same author or on renaming without new content.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The analysis relies entirely on standard mathematical tools of general relativity for spacetime classification; no free parameters, ad-hoc axioms, or new entities are introduced.

axioms (1)
  • standard math Petrov classification and Kundt spacetime definitions are standard and correctly applicable to electrovacuum metrics
    Invoked to establish type D Kundt character in the second paragraph of the abstract.

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Reference graph

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