Constraining interacting dark energy models with black hole superradiance

TL;DR

This work proposes black hole superradiance as a novel, independent probe of interacting dark-energy/dark-matter IDE models, motivated by hints of dynamical dark energy from DESI. It develops a general constraint framework that translates SR instability conditions for ultralight bosons into exclusion regions in IDE parameter spaces and applies it to two field-theoretic scenarios: (i) a DE scalar mediating a dark fifth force within the DM sector, and (ii) a DE field whose SR is induced by dense DM spikes around spinning black holes. The study demonstrates that current BH observations yield complementary, though currently loose, constraints on the DE-DM coupling and showcases how astrophysical black holes can test fundamental dark-sector physics beyond large-scale cosmology. It also establishes a methodological bridge between black hole physics and cosmology, paving the way for synergistic constraints as BH data improve. Overall, the results illustrate the viability and potential of BH superradiance as a high-sensitivity probe of dark-sector interactions.

Abstract

The recent preference for a dynamical dark energy (DE) from the Dark Energy Spectroscopic Instrument seems to call for interactions between DE and dark matter (DM), either from direct DM-DE interaction or indirect interaction induced by modified gravity. Therefore, an independent probe for these kinds of DE-DM interactions would be appealing from observational aspects. In this paper, we propose the black hole superradiance as a novel astrophysical probe for field-theoretic interacting DE-DM models, providing complementary constraints independent of large-scale cosmological observations. The core principle is that the DE-DM interaction can alter the effective mass of the superradiant ultralight boson, thereby modifying its superradiant instability rate around spinning black holes. We explore this connection through two distinct scenarios: a model where the DE field mediates a dark fifth force within the DM sector, affecting the superradiance from DM particles; and a novel mechanism where the DE field itself becomes superradiant due to the effective mass enhancement induced by dense DM spikes around supermassive black holes. By applying a statistical framework to black hole observations in both scenarios, we derive constraints on the fundamental DE-DM coupling strength. Although the current constraints are rather loose due to small samples and inaccurate measurements, our work provides new astrophysical constraints on these interacting DE-DM scenarios and establishes a new synergy between black hole physics and cosmology for probing the fundamental nature of the dark sector.

Figures (4)

• Figure 1: Normalised posterior probability density distributions for the DM mass $m_\chi$ and the coupling strength $\beta$, derived from observations of IRAS 09149-6206 (left) and M33 X-7 (right). The filled contours represent the results for our benchmark model with the DE mediator mass set to $m_\phi/H_0=1$, and the solid black lines indicate the corresponding 95% CRs at highest posterior density. For comparison, the dashed lines show the 95% CRs for models with alternative mediator masses of $m_\phi/H_0=2$ and $m_\phi/H_0=0.5$. Finally, the horizontal dashed line indicates the 95% C.L. cosmological upper limit on $\beta$ from Archidiacono et al. (2022) Archidiacono:2022iuu.
• Figure 2: Dark matter density profiles around a SMBH with the mass of M87* ($M = 6.5 \times 10^9 \mathrm{M}_{\odot}$). The solid line represents the DM spike profile resulting from an initial NFW halo ($\gamma=1$, $\gamma_{\mathrm{sp}}=7/3$), while the dashed line shows the steeper spike resulting from an initial $\gamma=2$ halo ($\gamma_{\mathrm{sp}}=5/2$). The density is shown as a function of the radial coordinate $r$. The density is shown as a function of the radial coordinate $r$, covering the range from the event horizon $r_+$ to the spike radius $R_{\mathrm{sp}}$.
• Figure 3: The real part $M\omega_R$ and imaginary part $M\omega_I$ of the frequency for the fundamental superradiant mode ($\ell=m=1$) and the $\gamma=1$ case. The frequencies are plotted as a function of the coupling parameter $\beta$ for three representative values of the BH spin: $\tilde{a}=0.95$ (top), $\tilde{a}=0.9$ (middle), and $\tilde{a}=0.85$ (bottom). A superradiant instability exists in the region where $\omega_I > 0$.
• Figure 4: The normalised posterior probability density distribution for the coupling parameter $\beta$, derived from M87* observations. A log-uniform prior was assumed for $\beta$. The shaded region represents the parameter space excluded at 95% confidence.