Webinar《On the kinematic cosmic dipole tension》

Our motion through the Universe generates a dipole in the temperature anisotropies of the Cosmic Microwave Background(CMB) and also in the angular distribution of sources. If the cosmological principle is valid, these two dipoles are directly linked, such that the amplitude of one determines that of the other. However, it is a longstanding problem that number counts of radio sources and of quasars at low and intermediate redshifts exhibit a dipole that is well aligned with that of the CMB but with about twice the expected amplitude, leading to a tension reaching up to 4.9 sigma. In this talk, the speaker revisits the theoretical derivation of the dipole in the sources number counts, explicitly accounting for the redshift evolution of the population of sources. He will argue that if the spectral index and magnification bias of the sources vary with redshift, the standard theoretical description of the dipole may be inaccurate. The speaker will provide an alternative expression which does not depend on the spectral index, but instead on the time evolution of the population of sources. He then determines the values that this evolution rate should have in order to remove the tension with the CMB dipole.

時間:2022.05.17(二) 21:00~22:20
頻道:(網上講授)Zoom ID:421-480-1692 ← cosmology
講者:Charles Dalang(University of Geneva)



“Copernicus Webinar and Colloquium Series”: To promote scientific discussions during this pandemic, they are organizing an online seminar series, i.e. Copernicus Webinar Series, seeking the most outstanding speakers to introduce innovative ideas and important progress in the field of gravity and cosmology. This series is named after the famous Polish Astronomer, Nicolaus Copernicus, whose discovery eventually marked the dawn of modern science.




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