Distinguishing coupled dark energy models with neural networks

Aims. We investigate whether neural networks (NNs) can accurately differentiate between growth-rate data of the large-scale structure (LSS) of the Universe simulated via two models: a cosmological constant and Λ cold dark matter (CDM) model and a tomographic coupled dark energy (CDE) model. Methods. We built an NN classifier and tested its accuracy in distinguishing between cosmological models. For our dataset, we generated fσ8(z) growth-rate observables that simulate a realistic Stage IV galaxy survey-like setup for both ΛCDM and a tomographic CDE model for various values of the model parameters. We then optimised and trained our NN with <ns0:monospace>Optuna</ns0:monospace>, aiming to avoid overfitting and to maximise the accuracy of the trained model. We conducted our analysis for both a binary classification, comparing between ΛCDM and a CDE model where only one tomographic coupling bin is activated, and a multi-class classification scenario where all the models are combined. Results. For the case of binary classification, we find that our NN can confidently (with > 86% accuracy) detect non-zero values of the tomographic coupling regardless of the redshift range at which coupling is activated and, at a 100% confidence level, detect the ΛCDM model. For the multi-class classification task, we find that the NN performs adequately well at distinguishing ΛCDM, a CDE model with low-redshift coupling, and a model with high-redshift coupling, with 99%, 79%, and 84% accuracy, respectively. Conclusions. By leveraging the power of machine learning, our pipeline can be a useful tool for analysing growth-rate data and maximising the potential of current surveys to probe for deviations from general relativity.