The Cosmological principle and the frame that never was
Mohamed Rameez
Niels Bohr Institute, University of Copenhagen
Abstract: The largest anisotropic feature of the Cosmic Microwave Background is the dipole, believed to originate from the relative motion of the heliocentric frame with a velocity of ~369 km/s with respect to the ‘rest frame of the Universe’ in standard cosmology. This should cause a dipolar modulation in the number counts of distant sources, through special relativistic aberration and Doppler boosting effects. We test this with various all-sky catalogues: NVSS and SUMSS radio galaxies, WISE galaxies and AGNs as well as GAIA-unWISE AGNs and consistently find a significantly larger dipole than expected, implying velocities > 1000 km/s at conservative statistical significances as high as 3.3 sigma. These and other observations hint at a bulk flow of matter in the local Universe, extending out to scales larger than is typical in \Lambda CDM N-body simulations. Convergence to the CMB rest frame has never been demonstrated. An observational effect of such a bulk flow would be a scale dependent dipolar modulation in the deceleration parameter. We look for this in the SDSS-II/SNLS-III Joint lightcurve analysis compilation of SN1a data and find such a modulation at ~3.9 sigma statistical significance, while the evidence for any isotropic acceleration of the Universe simultaneously drops to <1.4 sigma. These observations suggest that dark energy is an artefact of our idealized cosmological model.
یکشنبه 26 مرداد 1399، ساعت 19:00
Sunday 16 August, 2020 – 19:00 Tehran Time
اتاق سمینار مجازی –Virtual Seminar Room
https://vclass.ecourse.sharif.edu/ch/cosmology
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