March 21, 2023

Speaker: Colin Hill (Columbia University)

Contact Information: jch2200@columbia.edu

Title:  Searching for Cosmological Concordance with New Physics in the Dark Sector: Hints and Challenges

Abstract: I will discuss recent and ongoing work focused on attempts to restore concordance amongst cosmological data sets, motivated by discrepancies amongst some inferences of the cosmic expansion rate (H_0) and the matter clustering amplitude (S_8). I will explain why the most viable models to resolve the H_0 problem invoke new physics at or prior to the last scattering epoch. Such models include modified recombination scenarios, quasi-accelerating early dark energy (EDE) models (and extensions thereof, featuring EDE-dark matter interactions), or scenarios featuring new light particles with non-trivial interactions. I will present constraints on such scenarios derived using data from the Atacama Cosmology Telescope (ACT), the Planck satellite, and large-scale structure surveys. I will highlight newly obtained constraints on EDE models derived from Lyman-alpha forest data, which severely hinder the ability of this scenario to resolve the H_0 problem. I will conclude with a look ahead to forthcoming CMB analyses from ACT, which will provide a powerful test of these scenarios in the low-noise, high-resolution regime.

Visitor's room: Room 111A

Visit Schedule:

Tuesday (21 Mar. 2023):

• 9:30 a.m.: 

• 10:00 a.m:  

• 10:30 a.m.: 

• 11:00 a.m.: Colloquium 

• 11:30 a.m.: Colloquium 

• 12:00 p.m.: Bahcall lunch

• 12:30 p.m.: Bahcall lunch

• 1:00 p.m.: Bahcall lunch

• 1:30 p.m.:  Lyman Page (Jadwin)

• 2:00 p.m.: Tea Time with Grad Students in Grand Central

• 2:30 p.m.: Tea Time with Grad Students in Grand Central

• 3:00 p.m.: Jahmour Givans (108A)

• 3:30 p.m.: He Jia (013 Peyton)

• 4:00 p.m.: Rodrigo Cordova (111A)

• 4:30 p.m.: Jo Dunkley (111A)

• 5:00 p.m.:

Dinner Sign-up - add your name here:

Tuesday (21 Mar. 2023)

1. Faculty Host: Peter Melchior

2. Postdoc Host: Jahmour Givans

3.  He Jia

4. Jiaxuan Li

5. Roohi Dalal

6. Rodrigo Cordova

7. Robert Lupton

8. 
   

STUDENTS HAVE PRIORITY.

PLEASE NO MORE THAN 8 PEOPLE (it is more difficult to properly interact with the speaker in larger groups).