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Montani, G., De Angelis, M., Bombacigno, F., & Carlevaro, N. (2024). Metric f(R) gravity with dynamical dark energy as a scenario for the Hubble tension. Mon. Not. Roy. Astron. Soc., 527(1), L156–L161.
Abstract: We introduce a theoretical framework to interpret the Hubble tension, based on the combination of a metric f(R) gravity with a dynamical dark energy contribution. The modified gravity provides the non-minimally coupled scalar field responsible for the proper scaling of the Hubble constant, in order to accommodate for the local SNIa pantheon+ data and Planck measurements. The dynamical dark energy source, which exhibits a phantom divide line separating the low redshift quintessence regime (-1 < w < -1/3) from the phantom contribution ( w < -1) in the early Universe, guarantees the absence of tachyonic instabilities at low redshift. The resulting H-0(z) profile rapidly approaches the Planck value, with a plateau behaviour for z greater than or similar to 5. In this scenario, the Hubble tension emerges as a low redshift effect, which can be in principle tested by comparing SNIa predictions with far sources, like QUASARS and gamma ray bursts.
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Schiavone, T., Montani, G., & Bombacigno, F. (2023). f(R) gravity in the Jordan frame as a paradigm for the Hubble tension. Mon. Not. Roy. Astron. Soc., 522(1), L72–L77.
Abstract: We analyse the f(R) gravity in the so-called Jordan frame, as implemented to the isotropic Universe dynamics. The goal of the present study is to show that according to recent data analyses of the supernovae Ia Pantheon sample, it is possible to account for an effective redshift dependence of the Hubble constant. This is achieved via the dynamics of a non-minimally coupled scalar field, as it emerges in the f(R) gravity. We face the question both from an analytical and purely numerical point of view, following the same technical paradigm. We arrive to establish that the expected decay of the Hubble constant with the redshift z is ensured by a form of the scalar field potential, which remains essentially constant for z less than or similar to 0.3, independently if this request is made a priori, as in the analytical approach, or obtained a posteriori, when the numerical procedure is addressed. Thus, we demonstrate that an f(R) dark energy model is able to account for an apparent variation of the Hubble constant due to the rescaling of the Einstein constant by the f(R) scalar mode.
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