Forecasting gravitational wave tests of f(Q, T) modified gravity

Gravitational waves have become one of the most powerful independent probes of gravity beyond General Relativity, and a new theoretical study asks what future detections could reveal about a class of modified gravity known as f(Q, T) gravity. Because both quantities enter the field equations, the theory modifies how matter and geometry couple, altering the way gravitational waves propagate across an evolving universe. The research, published in General Relativity and Gravitation by S. Davood Sadatian, Zahra Davari and S. Mohamad Reza Hosseini, derives the gravitational wave propagation equation within a separable f(Q, T) framework and computes the corresponding modified gravitational wave luminosity distance induced by the altered cosmological background evolution.

Rather than analyzing real observations, the team conducted a forecast study built on a fiducial ΛCDM mock cosmology. They generated simulated gravitational wave standard-siren catalogs corresponding to three detector generations: current LIGO-Virgo instruments, the planned space-based LISA observatory, and the next-generation Einstein Telescope. The authors considered two representative functional forms of f(Q, T) and constrained their parameters using mock GW standard-siren datasets for each detector configuration.

The analysis emphasizes that the resulting parameter estimates are sensitivity indicators for the adopted mock realization rather than definitive observational constraints. This distinction matters: the numbers describe how well future catalogs could in principle pin down the model, given the assumed fiducial cosmology, not what the universe has actually been measured to do. The forecast results show that increasing the number of standard sirens substantially improves sensitivity to the background cosmological parameters, with an Einstein Telescope-like catalog delivering the most pronounced gains.

Significant degeneracies remain, however, among the parameters describing the non-metricity sector and the matter-geometry coupling. In practical terms, different combinations of the model's free functions can produce nearly indistinguishable gravitational wave signatures, meaning that even a rich standard-siren catalog may not fully disentangle the individual contributions of Q and T to the gravitational action. The study highlights the strong potential of next-generation gravitational wave cosmology to test the fundamental nature of gravity and assess the viability of f(Q, T) gravity.

Because the gravitational wave propagation equation and the luminosity distance are derived directly from the modified field equations, the framework connects detector-level observables to the deepest layer of the theory, where the roles of non-metricity and the energy-momentum trace are encoded. The authors note that their results demonstrate the prospective sensitivity of future observations to the model parameters, while the persistence of degeneracies in the non-metricity and coupling sectors marks the key challenge for turning mock forecasts into genuine tests of modified gravity.

Subject of Research: Gravitational wave signatures and forecasts in f(Q, T) modified gravity

Article Title: Gravitational wave signatures and forecasts in f(Q, T) modified gravity

Article References: Sadatian, S. D., Davari, Z., & Hosseini, S. M. R. (2026). Gravitational wave signatures and forecasts in f(Q, T) modified gravity. General Relativity and Gravitation, 58(10), Article 124. https://doi.org/10.1007/s10714-026-03628-w

Image Credits: AI Generated

DOI: 10.1007/s10714-026-03628-w

Keywords: Gravitational, wave, signatures, forecasts, modified, gravity, scientific research