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Peer-reviewedCC BY 4.0The European Physical Journal C

Equatorial periodic orbits and gravitational wave phenomenology around spherically-symmetric vacuum solution in Freund–Nambu scalar–tensor gravity

  • Dhruba Jyoti Gogoi1,2
  • Jyatsnasree Bora1
  • Himanshu Chaudhary3
  • M. Yousaf4,5
  • G. Mustafa6
6 affiliations
  1. 1Madhabdev University
  2. 2Khazar University
  3. 3Babeş-Bolyai University
  4. 4Virtual University of Pakistan
  5. 5University of Management and Technology
  6. 6Zhejiang Normal University
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Abstract

We investigate test particle dynamics and gravitational wave (GW) phenomenology in an exact spherically symmetric vacuum solution of Freund–Nambu scalar–tensor gravity. This framework generalizes the Janis–Newman–Winicour (JNW) naked singularity via a geometric non-linear coupling q and a direct scalar-particle coupling gs g s . We demonstrate that these parameters systematically modify the Innermost Stable Circular Orbit (ISCO) – which shifts inward for gs > 0 g s > 0 – and the Marginally Bound Orbit (MBO). Furthermore, we classify bound periodic trajectories to isolate extreme zoom–whirl orbits exhibiting intense periapsis precession. By applying the Numerical Kludge method to Extreme Mass-Ratio Inspirals (EMRIs), we reveal that scalar–tensor corrections induce a macroscopic temporal dephasing in high-frequency GW bursts, even when the orbit’s spatial topology is preserved. These unique phase shifts offer a robust diagnostic signature for future space-based observatories like LISA to probe the strong-field regime and constrain scalar–tensor extensions of general relativity.

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Cite

BibTeXRIS
BibTeX
@article{gogoi2026equatorial,
  title = {{Equatorial periodic orbits and gravitational wave phenomenology around spherically-symmetric vacuum solution in Freund–Nambu scalar–tensor gravity}},
  author = {Dhruba Jyoti Gogoi and Jyatsnasree Bora and Himanshu Chaudhary and M. Yousaf and G. Mustafa},
  journal = {The European Physical Journal C},
  year = {2026},
  month = oct,
  doi = {10.1140/epjc/s10052-026-16451-z},
  url = {https://link.springer.com/article/10.1140/epjc/s10052-026-16451-z},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Equatorial periodic orbits and gravitational wave phenomenology around spherically-symmetric vacuum solution in Freund–Nambu scalar–tensor gravity
AU  - Dhruba Jyoti Gogoi
AU  - Jyatsnasree Bora
AU  - Himanshu Chaudhary
AU  - M. Yousaf
AU  - G. Mustafa
PY  - 2026
DA  - 2026/10/19
JO  - The European Physical Journal C
DO  - 10.1140/epjc/s10052-026-16451-z
UR  - https://link.springer.com/article/10.1140/epjc/s10052-026-16451-z
AB  - We investigate test particle dynamics and gravitational wave (GW) phenomenology in an exact spherically symmetric vacuum solution of Freund–Nambu scalar–tensor gravity. This framework generalizes the Janis–Newman–Winicour (JNW) naked singularity via a geometric non-linear coupling q and a direct scalar-particle coupling g_s g s . We demonstrate that these parameters systematically modify the Innermost Stable Circular Orbit (ISCO) – which shifts inward for g_s > 0 g s > 0 – and the Marginally Bound Orbit (MBO). Furthermore, we classify bound periodic trajectories to isolate extreme zoom–whirl orbits exhibiting intense periapsis precession. By applying the Numerical Kludge method to Extreme Mass-Ratio Inspirals (EMRIs), we reveal that scalar–tensor corrections induce a macroscopic temporal dephasing in high-frequency GW bursts, even when the orbit’s spatial topology is preserved. These unique phase shifts offer a robust diagnostic signature for future space-based observatories like LISA to probe the strong-field regime and constrain scalar–tensor extensions of general relativity.
SN  - 1434-6044
SN  - 1434-6052
ER  -