{
  "abstract": "We construct the Kaluza-Klein electric dressing of the Tomimatsu-Sato $δ=2$ vacuum spacetime by uplifting to five dimensions, boosting along the compact direction and reducing to Einstein-Maxwell-dilaton theory with coupling $a=\\sqrt3$. It carries a nontrivial dilaton, unlike the known Einstein-Maxwell charged and magnetized Tomimatsu-Sato solutions. At leading order it shares the mass-charge-dilaton relations and gyromagnetic ratio $g=2-\\tanh^2α$ of the boosted Kerr black hole; the seed first shows up in the quadrupole. Using Mayerson's non-vacuum Geroch-Hansen multipoles, we derive the exact law $M_2(α)=\\frac12(1+\\cosh^2α)M_2^{(0)}$, so the $δ=2$ quadrupole excess $ΔM_2=-\\frac14p^2m^2M$ survives every boost. In the Kodama-Hikida picture the Weyl segment $ρ=0$, $|z|<κ$ is a singular rod with degenerate Killing horizons at its endpoints. There the boost function equals $\\coshα$, so the near-horizon geometry is a constant rescaling of the seed's: the horizons stay degenerate and non-rotating, their areas and Komar angular momenta scale by $\\coshα$, and the electric potential is $\\frac12\\tanhα$. The electric flux through any closed surface is $\\sinhα\\coshα$ times the enclosed seed Komar mass, so the horizons and the ring singularity are uncharged and the rod carries all the charge; the boost-invariant identity $M-Φ_eQ=m$ follows. The ergosurface stays at $f=0$; a new curvature-singular boundary appears at $f=\\coth^2α$, where the Kaluza-Klein circle becomes null. As the seed potential $f$ is unbounded above near the ring, it exists for every nonzero boost: unlike for Kerr, no Kaluza-Klein boost of TS$_2$ is a spacelike reduction everywhere. The excised region is compact, has the ring on its boundary and never reaches the horizons. Charging pointwise strengthens the causality violation near the rod.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.29277",
  "author_total": 2,
  "authors": [
    {
      "name": "Haryanto M. Siahaan"
    },
    {
      "name": "Masoud Ghezelbash"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/63t8jaapz17dd.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.29277",
  "fulltext_url": null,
  "id": "63t8jaapz17dd",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.29277",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "gr-qc"
    ],
    [
      "openalex",
      "3106|Black Holes and Theoretical Physics"
    ]
  ],
  "openalex": "W7223225804",
  "pdf_url": "https://arxiv.org/pdf/2610.29277",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-21",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/63t8jaapz17dd.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:19Z",
      "native_id": "2610.29277",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.29277"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "Tomimatsu--Sato $δ=2$ Solution in Kaluza--Klein Theory",
  "title_text": "Tomimatsu--Sato δ=2 Solution in Kaluza--Klein Theory",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:19Z",
  "url": "https://research.draconitic.com/paper/63t8jaapz17dd",
  "venue": "arXiv",
  "versions": []
}