Big Bang Nucleosynthesis in Constrained f ( Q,C ) Gravity: An Observational Analysis

The construction of gravity is based on symmetric teleparallel geometry, which involves the boundary term despite the Ricci scalar along with non‐metricity . In this article, we are devoted to assess the effects of gravity for the formation of light elements in the early‐universe known as big bang nucleosynthesis. For instance, we examine the big bang nucleosynthesis constraints in four distinct gravity models. Specifically, we investigate how the modifications by the boundary term and non‐metricity influence the freeze‐out temperature , comparing with the standard results. We focus on four distinct cosmological models of gravity involving linear, nonlinear, and composite terms of and . We further examine the implications of these modifications on the primordial helium abundance , constraining the model parameters using current observational limits and complement this analysis by studying the evolution of the expansion‐rate ratio , which provides a clear diagnostic of how each model departs from standard cosmology during the radiation‐dominated era. Overall, the considered models in the context of gravity meet the big bang nucleosynthesis constraints, establishing viable cosmologies, which are capable of describing the evolution of the universe properly.