State of the Universe

Observational indications of an apparent cosmic acceleration from the SNIa data

by Dr. Kerkyra Asvesta (Aristotle University of Thessaloniki)

Wednesday, May 15, 2024 from to (Asia/Kolkata)
at AG80 and https://us02web.zoom.us/j/82512956967?pwd=angyQ0ZDdHZUdzFUbjkybmxsWFNFUT09 Meeting ID: 825 1295 6967 Passcode: 384194
Description Although the ΛCDM model still remains the standard fit to the available cosmological data and provides an explanation for the late-time acceleration, there are still open questions that motivate alternative scenarios.

This work looks into the implications of bulk peculiar motions for the interpretation of the recent accelerated expansion. We employ a tilted cosmological model with two families of observers/frames. The first follows the Hubble flow and the second is the frame of real observers, moving relative to the universal expansion with non-relativistic peculiar velocities. Using the Pantheon compilation of Type Ia supernovae, we show that the tilted model can reproduce the late-time cosmic acceleration without the need of a Cosmological Constant, without modifying General Relativity and without abandoning the Friedmann models. We also discuss the predictions of the tilted scenario. Among them is the presence of an apparent dipolar anisotropy in the sky distribution of the deceleration parameter, with a redshift-decaying magnitude.