In this study, we utilize a parametrization of the deceleration parameter within a tilted universe, namely a cosmological model equipped with two families of observers moving relative to each other with finite peculiar velocities. Using the Pantheon dataset, we study the redshift evolution of the deceleration parameter. We demonstrate that a tilted cosmological model can reproduce the recent acceleration history of the universe, without invoking a cosmological constant or dark energy, by simply accounting for the linear effects of peculiar motions. Additionally, we study the dipolar behavior in the deceleration parameter within this framework. Leveraging the Pantheon+SHOES Type Ia supernova dataset, we explore the potential anisotropies in the cosmic acceleration. Building on previous work, we adopt an exponentially decaying dipole model aligned with the direction of the Cosmic Microwave Background (CMB) dipole. A Bayesian statistical approach, employing a Markov Chain Monte Carlo (MCMC) method, is used to derive the posterior distributions of the model parameters. Our findings indicate that the dipole moment in the deceleration parameter is significant. This suggests that the anisotropic signatures could influence the interpretation of cosmic acceleration.

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Apparent Acceleration and Doppler-Like Dipole in the Observed q-Distribution

  • Kerkyra Asvesta

摘要

In this study, we utilize a parametrization of the deceleration parameter within a tilted universe, namely a cosmological model equipped with two families of observers moving relative to each other with finite peculiar velocities. Using the Pantheon dataset, we study the redshift evolution of the deceleration parameter. We demonstrate that a tilted cosmological model can reproduce the recent acceleration history of the universe, without invoking a cosmological constant or dark energy, by simply accounting for the linear effects of peculiar motions. Additionally, we study the dipolar behavior in the deceleration parameter within this framework. Leveraging the Pantheon+SHOES Type Ia supernova dataset, we explore the potential anisotropies in the cosmic acceleration. Building on previous work, we adopt an exponentially decaying dipole model aligned with the direction of the Cosmic Microwave Background (CMB) dipole. A Bayesian statistical approach, employing a Markov Chain Monte Carlo (MCMC) method, is used to derive the posterior distributions of the model parameters. Our findings indicate that the dipole moment in the deceleration parameter is significant. This suggests that the anisotropic signatures could influence the interpretation of cosmic acceleration.