Distinguishing Distance Duality breaking models using electromagnetic and gravitational waves measurements

TL;DR

This work investigates how upcoming gravitational-wave standard sirens, when combined with BAO and Type Ia supernovae, can test the distance duality relation (DDR) and distinguish whether potential violations arise from electromagnetic processes or gravitational physics. It explores phenomenological DDR deviations using constant $\epsilon$ and Padé parametrizations, within two frameworks: Universal Violation Scenario (UVS) and Independent Violation Scenario (IVS). Using synthetic data for the Einstein Telescope, SKA2 BAO, and LSST-like SNe, the study finds that GW distances provide constraining power comparable to SNe when BAO anchors are included, and that joint EM+GW observations can discriminate the physical origin of DDR violations. The Padé approach is shown to be robust within the redshift range considered, and the work highlights the value of multi-messenger data for identifying whether DDR breaking occurs in the electromagnetic sector or in the gravitational sector, guiding future theoretical and observational efforts.

Abstract

Several assumptions at the foundation of the standard cosmological model have as a direct consequence a specific relation between cosmological distances, known as the distance duality relation, whose violation would be a smoking gun of deviations from standard cosmology. We explore the role of upcoming gravitational wave observations in investigating possible deviations from the distance duality relation, alongside the more commonly used supernovae. We find that, when combined with baryon acoustic oscillations, gravitational waves will provide similar constraining power to the combination of baryon acoustic oscillations and supernovae. Moreover, the combination of observables with different sensitivities to electromagnetic and gravitational physics provides a promising way to discriminate among different physical mechanisms that could lead to violations of the distance duality relation.

Figures (6)

• Figure 1: Comparison of the behaviour of $\eta(z)$ using the Padé expression (blue) and the constant $\epsilon$ expression. The inset shows a zoomed-in view of the redshift range relevant for this work. The horizontal grey line marks $\eta = 1$, and the vertical dashed grey line indicates the redshift of the Last Scattering Surface $z_*$.
• Figure 2: (a) : Two-dimensional contours on $\Omega_m$ and $\epsilon_0^{EM}$ using BAO (green) and SN (orange). (b) : Two-dimensional contours on $\Omega_m$ and $\epsilon_0^{GW}$ using BAO (green) and GW (blue). Both results are obtained using the synthetic data described in \ref{['sec:data']} and the methodology described in \ref{['sec:method']}.
• Figure 3: Detected GW events as a function of redshift and inclination angle $\theta_\nu$, along with their corresponding peak flux. The events are simulated assuming a fiducial cosmology from Pantheon+SH0ES Riess_2022, with $H_0=73.4$ and $\Omega_m=0.306$. The grey points represent events detected by ET that survive the SNR cut, while the coloured points indicate events that would also be detected with an associated electromagnetic counterpart.
• Figure 4: (a) : Error associated with the UVS parameter $\epsilon_0$ for different combinations of observables, shown for both the $\Lambda$CDM case (solid blue) and the breaking case (dashed pink). (b) : Constraints in the $\epsilon_0$–$\Omega_m$ parameter space obtained assuming a universal violation scenario (UVS) affecting both the electromagnetic and gravitational sectors. If the true physical behavior instead involves a violation only in the electromagnetic sector, applying the UVS framework can artificially induce a tension in $\epsilon_0$ between the BAO+SN and BAO+GW datasets.
• Figure 5: Constraints in the $\epsilon_0^{\rm EM}$–$\epsilon_0^{\rm GW}$ parameter space for three different physical scenarios: $\Lambda$CDM (orange), violation in the electromagnetic sector only (pink), and violation in both the electromagnetic and gravitational sectors (blue). The black dashed line represents the case $\epsilon_0^{\rm EM} = \epsilon_0^{\rm GW}$.