Cosmology of Quadratic Metric-Affine Gravity

Abstract

We investigate the cosmological aspects of the most general parity preserving Metric-Affine Gravity theory quadratic in torsion and non-metricity in the presence of a cosmological hyperfluid. The equations of motion are obtained by varying the action with respect to the metric and the independent affine connection. Subsequently, considering a Friedmann-Lemaître-Robertson-Walker background, we derive the most general form of the modified Friedmann equations for the full quadratic theory. We then focus on a characteristic sub-case involving only two quadratic contributions given in terms of torsion and non-metricity vectors. In this setup, studying the modified Friedmann equations along with the conservation laws of the perfect cosmological hyperfluid, we provide exact solutions both for purely dilation and for purely spin hypermomentum sources. We then discuss the physical consequences of our model and the prominent role of torsion and non-metricity in this cosmological setup.

arXiv comment29 pages. Accepted for publication in Phys. Rev. D

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• Coupling Metric-Affine Gravity to a Higgs-Like Scalar Field
• Vector stability in quadratic metric-affine theories
• Describing metric-affine theories anew: alternative frameworks, examples and solutions
• Metric-Affine Vector-Tensor Correspondence and Implications in $F(R,T,Q,\mathcal{T},\mathcal{D})$ gravity
• Quadratic Metric-Affine Gravity: Solving for the Affine-Connection
• Friedmann-like universes with non-metricity
• Cosmology of Metric-Affine $R+\beta R^2$ Gravity with Pure Shear Hypermomentum