Egypt

Tahia Dabash

United States

Moataz Emam

Germany

Lukas Schöppner

Reply to “Comment on: Symmetry and conserved quantities in $\textit{f}$($\textit{R}$)-gravity: Mei vs. Noether approaches”

We study the gravitational edge modes (GrEMs) and gauge edge modes (GaEMs) in Jackiw-Teitelboim (JT) gravity on a wiggling boundary. The wiggling effect manifests as a series of spacetime topological and bulk constraints for both conical and wormhole defect solutions. For the conical defect solution, we employ the generalized Fefferman-Graham (F-G) gauge to extend the boundary action, allowing for non-constant temperature and horizon position. We find that the infrared behavior of this boundary action is determined by the local dynamics of the temperature and horizon. For the wormhole defect solution, the boundary action can, in special cases, be described by a field with variable mass subject to a constant external force. We classify this corner system as a first-class constrained system influenced by field decomposition, confirming that the physical degrees of freedom are determined by constraints from the wiggling boundary information. We find that GrEMs and GaEMs can be linked at the corners by imposing additional constraints. Additionally, we show that the “parallelogram” composed of corner variables exhibits discreteness under a unitary representation. Finally, we explore that information from extrinsic vectors can be packaged into the GaEMs via a Maurer-Cartan form, revealing the boundary degrees of freedom as two copies of the $$ \mathfrak{sl}\left(2,\mathbb{R}\right) $$ algebra. By separating pure gauge transformations, we identify the gluing condition for gauge invariance and the corresponding integrable charges.

China

Kang Liu

Shoupan Liu

Xiao-Mei Kuang

Wiggling boundary and corner edge modes in JT gravity with defects

Testing Lorentz symmetry in strong gravitational fields provides a unique probe of extensions to standard model. The orbital motions of the S-stars around the supermassive black hole Sgr A* provide a natural laboratory for such tests. In this paper, we analyze the S2 orbital data focusing on a static and spherically symmetric black hole within Kalb–Ramond gravity, where the deviations from general relativity are encoded in a single Lorentz-violating parameter ℓ introduced by the Kalb–Ramond tensor field. Using a full 14-dimensional Markov Chain Monte Carlo analysis under uniform and Gaussian priors, we obtain <math altimg='si41.svg'><mrow><mi>&#8467;</mi><mo linebreak='goodbreak'>=</mo><msubsup><mrow><mn>1.60</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>5</mn></mrow></msup></mrow><mrow><mo>&#8722;</mo><mn>1.76</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow><mrow><mo>+</mo><mn>1.38</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow></msubsup></mrow></math> and <math altimg='si42.svg'><mrow><mi>&#8467;</mi><mo linebreak='goodbreak'>=</mo><msubsup><mrow><mo>&#8722;</mo><mn>1.02</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>5</mn></mrow></msup></mrow><mrow><mo>&#8722;</mo><mn>1.19</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow><mrow><mo>+</mo><mn>1.26</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow></msubsup></mrow></math> at 1 <italic>&#963;</italic> confidence level, respectively. These constraints are about three orders of magnitude tighter than those from Event Horizon Telescope imaging of Sgr A*. We also perform MCMC simulation by fitting data of S38 and S55 stars, as well as their joint analysis. Our results show that the best fit values of &#8467; in all simulations are always of <math altimg='si43.svg'><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>5</mn></mrow></msup></math> order, but S2 star provides the most stringent constraints on the parameters because S2 star has higher precision observational data comparing to the fewer public data for other two stars.

Qi Qi

Yu Sang

Detecting Lorentz-violation induced by a tensor field with S-star’s motion around Sgr A*

This study investigates the ultraviolet realization of semileptonic four-fermion operator $ O_{ledq}^{\alpha \beta 11} $ that incorporates Majorana dark matter (DM) in both lepton-flavor-conserving (LFC) and lepton-flavor-violating (LFV) scenarios at the one-loop level via box diagram, thereby effectively alleviating the lower bounds on the new physics scale. In addition, we investigate the interplay between model-independent constraints on the Wilson coefficients and DM direct detection, relic density, and collider searches in the context of fermion portal DM model with two mediators. We found that both the projected future constraint on the LFC Wilson coefficient $ C_{ledq}^{2211}/\Lambda^2 \lt $ $ (12.3\; \text{TeV})^{-2} $ from the measurements of neutrino non-standard interaction in the next-generation neutrino oscillation experiments, and the LFV constraint $ C_{ledq}^{1211}/\Lambda^2 \lt \left(2.2\times 10^3\; \text{TeV} \right)^{-2} $ from ongoing charged-lepton-flavor-violation searches, provide a complementary exploration of the parameter space encompassing the DM and scalar masses. With a colored mediator mass of approximately $ 2\; \text{TeV} $ , the sensitivity of the indirect constraints on the four-fermion operator can surpass those of collider searches and DM direct detection, in scenarios where the masses of the DM and scalar are close. By ensuring the correct DM relic density, however, we find that the collider searches and DM direct detection are more sensitive to the electroweak-scale DM and scalar than indirect constraints.

Yuxuan He

Gang Li

Jia Liu

Xiao-Ping Wang

Xiang Zhao

Lepton flavor of four-fermion operator and fermion portal dark matter * Gang Li and Xiang Zhao are supported by the National Natural Science Foundation of China (12347105, 12505127), the Guangdong Basic and Applied Basic Research Foundation (2024A1515012668). The work of Jia Liu is supported by the National Science Foundation of China (12235001, 12475103) and State Key Laboratory of Nuclear Physics and Technology (NPT2025ZX11). The work of Xiao-Ping Wang is supported by National Science Foundation of China (12375095) and the Fundamental Research Funds for the Central Universities

We investigate quasi-periodic oscillations (QPOs) as a diagnostic tool for probing frame-dragging effects and accretion disk physics in the spacetime of a rotating regular magnetic black hole (BH). Specifically, we analyze the precession of bound orbits and the epicyclic oscillations of test-particles under small perturbations in the equatorial plane. We demonstrate how the BH’s nonminimal coupling parameter ( $$\lambda /M^4$$ ) and dimensionless magnetic charge ($\textit{Q}$/$\textit{M}$) significantly influence the three fundamental epicyclic frequencies. By applying the relativistic precession model and employing Markov Chain Monte Carlo simulations (MCMC), we constrain the BH’s characteristic parameters, including mass, spin, magnetic charge, and nonminimal coupling, with the use of observational QPO data from five X-ray binaries: $$GRO J1655-40$$ , $$XTE J1859+226$$ , $$H1743-322$$ , $$XTE J1550-564$$ , and $$GRS 1915+105$$ . Furthermore, we examine the Lense-Thirring, geodetic, and general spin precession frequencies of a test gyroscope attached to a stationary observer around the current BH. Our theoretical results indicate that the regular charged BH suppresses these precession frequencies compared with the Kerr BH case.

R. Ali

Meng-He Wu

South Korea

Hong Guo

Precessions and parameter constraints from quasiperiodic oscillations in a rotating charged black hole

In this paper, we analyze the light rays and thin accretion imaging of a Yukawa-like black hole using the ray-tracing approach. We first find that as the Yukawa-like parameters have significant influences on the black hole’s photon sphere, critical impact parameter, and ranges of photon ring and lensed ring emissions. However, for certain values of these parameters, these quantities coincide with those of a Schwarzschild black hole, indicating a degeneracy in the optical appearance. Then by illuminating this black hole by various static, thin accretion flows, we investigate the observed intensity distribution and construct its shadow and images for selected parameters. Overall, the optical appearance of the Yukawa-like black hole is closely resembles that of Schwarzschild black hole, but the parameters significantly influence the size and brightness of the shadow and the photon rings. This suggests the degeneracy in the observational appearance between Yukawa-like black hole with specific parameters and Schwarzschild black hole. We expect that our preliminary findings could promote some insights for the future study and observational tests of the Yukawa-like gravitational potential.

Jia-Hao Ren

Ming-Jie Mao

Yuan Meng

Shadow and image from static and thin accretions of Yukawa-like black hole

We review the recent work by T.F. Dabash, M. Emam, and L. Schöppner (Eur. Phys. J. C 85, 1341, 2025) and identify an essential error in their analysis.

South Africa

Chile

Andronikos Paliathanasis

Comment on: “Symmetry and conserved quantities in $$f\left( R\right) $$ -gravity: Mei vs. Noether approaches”

In this article, we investigate the bound orbits of the timelike particles and the gravitational waveforms emitted from these orbits around a renormalization group improved Kerr black hole in the framework of the asymptotic safety approach. The running Newton coupling in the metric is characterized by two free quantum parameters $$(\omega ,\,\gamma )$$ arising from the non-perturbative renormalization group theory and the appropriate cutoff identification, respectively. As expected, the radii of the horizon, the marginally bound orbits and the innermost stable orbit are all decrease as the quantum parameters increase. Under the extreme mass-ratio inspirals approximation the deviation of gravitational waveforms radiated by the periodic orbits from those in the classical Kerr background increases with the two quantum parameters. However, this effect is much smaller in the retrograde case compared to the prograde case. Especially, by comparing the characteristic strain of those gravitational wave with the sensitivity curve of several potential detectors, we find that their characteristic frequencies can fall within the sensitivity ranges of several planned gravitational wave observatories, suggesting that such signals may be detectable with sufficient instrumental sensitivity.

Yong-Zhuang Li

The bound orbits and gravitational waveforms of timelike particles around renormalization group improved Kerr black holes

In this paper, we perform small perturbations around the circular timelike orbit in the equatorial plane of the Horndeski rotating black hole, and analyze the effects of Horndeski hair on the three fundamental frequencies of the epicyclic oscillations. Since this operation can model the quasiperiodic oscillations (QPOs) phenomena of the surrounding accretion disc, we then employ the MCMC simulation to fit the theoretical results with three QPO events, including GRO J1655-40, XTE J1859+226 and H1743-322, and constrain the characteristic radius $\textit{r}$, black hole mass $\textit{M}$ and spinning parameter $\textit{a}$, and the Horndeski hair parameter $\textit{h}$. Our constraint on the Horndeski hair parameter is much tighter than QPOs simulation from the existed accretion models, suggesting slight deviation from classical Kerr black hole.

Parameter constraints on Horndeski rotating black hole through quasiperiodic oscillations

In this work, we demonstrate that the hyperboloidal foliation technique, applied to the study of black hole quasinormal modes, where the spatial boundary is shifted from spacelike infinity to the future event horizon and null infinity, is effectively equivalent to the continued fraction approach, in which the asymptotic wave function typically diverges at both ends of spatial infinity. Specifically, a given hyperboloidal slicing, corresponding to a particular choice of coordinates, always uniquely determines a scheme for extracting the asymptotic form of the wave function at the spatial boundary. Owing to the mathematical equivalence, it follows that the efficiency and precision observed using the hyperboloidal approach should be attributed, not to avoiding the pathological behavior at the spatial boundaries, but primarily to other factors, such as the use of Chebyshev grids.