Causal viscous-fluid driven non-singular cosmological bounces in modified gravity

The resolution of cosmological singularities remains a central challenge in the physics of the dark Universe, where dissipative effects may provide a natural alternative to exotic matter fields. We demonstrate that causal bulk-viscous fluids, governed by the Israel–Stewart theory, can generate non-singular cosmological bounces that remain stable and thermodynamically consistent. Starting from the Eckart no-go theorem, we derive analytical bounce conditions and confirm their validity through numerical integrations of parametrized scale factors. The finite relaxation time induces a controlled violation of the null energy condition while ensuring positive entropy production and finite viscous pressure at the bounce. When extended to [Formula: see text] gravity and Loop Quantum Cosmology (LQC), higher-curvature and quantum-geometry corrections further enhance the robustness of these causal bounces. The framework thereby establishes dissipative transport as a physically motivated mechanism for singularity resolution, potentially linking early-Universe dynamics to observable imprints on primordial perturbations.