Dartmouth Events

Physics & Astronomy Cosmology Seminar - Vivian Poulin, CNRS

Title: "CMB, LSS and the Distance Ladder: Cosmic Discordance?"

9/9/2021
12 pm – 1 pm
Zoom: Email for link and password
Intended Audience(s): Public
Categories: Lectures & Seminars
Abstract: The Lambda-cold-dark-matter (LCDM) model has established itself as a fantastic —yet parametric—  concordance model able to adjust a wide variety of observables (BBN, CMB, BAO most notably).  However as the precision of data has increased over the past few years, a number of predictions of the LCDM model are challenged by recent observations.
First and foremost, the infamous 'Hubble tension’ is a strong mismatch between the value of the Hubble constant measured using the classical distance ladder method and that inferred from the ΛCDM model. Second, the ‘S8 tension’ is a longstanding discrepancy between the determination of the amplitude of matter fluctuations on a 8 Mpc/h scale, parameterized as S8 ≡ σ8(Ωm/0.3)0.5, by galaxy (weak lensing) surveys and its prediction within the LCDM model.  

After a brief review of the various measurements (and some potential short-comings), I will discuss potential implications that such measurements could have. I will argue that current data favor the possibility that our Universe has undergone anomalous expansion just before recombination and present an overview of the most promising models (early dark energy, exotic recombination, curvature, additional dark radiation and new neutrino properties), and their current limitations.  I will present guidelines to resolving these tensions simultaneously and suggest what it would take to establish a new `concordance model’ beyond LCDM.

For more information, contact:
Tressena Manning
tressena.a.manning@dartmouth.edu
603-646-2854
Permanent URL to this event: https://physics.dartmouth.edu/events/event?event=64631

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