Looking for extra dimensions in the observed quasi-periodic oscillations of black holes

TL;DR

This study investigates how extra spatial dimensions could influence black hole quasi-periodic oscillations, using observational data to estimate a tidal charge parameter that signals the presence of extra dimensions.

Contribution

It introduces a method to analyze QPOs in rotating braneworld black holes and constrains the tidal charge parameter using observational data, indicating potential evidence for extra dimensions.

Findings

Most models predict a negative tidal charge parameter.

Observations are consistent with negative tidal charge within 1-sigma confidence.

Eight out of eleven models favor negative tidal charge values.

Abstract

Quasi-periodic oscillations, often present in the power density spectrum of accretion disk around black holes, are useful probes for the understanding of gravitational interaction in the near-horizon regime of black holes. Since the presence of an extra spatial dimension modifies the near horizon geometry of black holes, it is expected that the study of these quasi-periodic oscillations may shed some light on the possible existence of these extra dimensions. Intriguingly, most of the extra dimensional models, which are of significant interest to the scientific community, predicts the existence of a tidal charge parameter in black hole spacetimes. This tidal charge parameter can have an overall negative sign and is a distinctive signature of the extra dimensions. Motivated by this, we have studied the quasi-periodic oscillations for a rotating braneworld black hole using the available theoretical models. Subsequently, we have used the observations of the quasi-periodic oscillations from available black hole sources, e.g., GRO J1655 -- 40, XTE J1550 -- 564, GRS 1915 + 105, H 1743 + 322 and Sgr A* and have compared them with the predictions from the relevant theoretical models, in order to estimate the tidal charge parameter. It turns out that among the 11 theoretical models considered here, 8 of them predict a negative value for the tidal charge parameter, while for the others negative values of the tidal charge parameter are also well within the 1-$\sigma$ confidence interval.