# Institute for Advanced Study/Princeton University Early Universe/Cosmology Lunch Discussion

## Topic 1: Seeking solutions for the Hubble tension Topic 2: Likelihood approximations for (future) large angular scale CMB data

Abstract 1: Despite the success of LCDM model, there is a growing tension between measurements of the current expansion rate from the local distance ladder and from the cosmic microwave background (CMB). Known as the $H_0$ tension, this observational discrepancy presents a possible challenge to LCDM and has become an increasingly significant mystery to solve in recent years.
In this seminar, I will talk about the currently proposed solutions for the Hubble tension, and particularly focus on Acoustic Dark Energy (an Early Dark Energy-like) model. Acoustic Dark Energy model could provide the high H0 solution with a simple scalar field realization. The possible paths to better solutions in the future will also be talked about.

Abstract 2: In this seminar, I will talk about challenges arising in cosmological data analysis: an accurate representation of the likelihood, as well as the ability to model systematics are crucial in order to make reliable inference. Exact likelihoods are either unknown or intractable. I will discuss how we can make reliable inference from noise and systematics dominated signals, such as the optical depth to reionization (tau) or primordial gravitational waves, parametrised by the tensor-to-scalar ratio (r), from large-scale CMB data. The presented methods range from likelihood-approximations to simulation-based approaches to constrain cosmological parameters. The developed methods will be required for next-generation CMB surveys.

REGISTRATION

### Date & Time

December 06, 2021 | 12:30pm – 2:00pm

### Location

Zoom; PU, Peyton Hall 205

### Speakers

Meng-Xiang Lin and Roger de Belsunce

### Speaker Affiliation

KICP, University of Chicago and KICP, Cambridge