October 28, 2025

Speaker: Pedro Ferreira (Oxford)

Contact Information: 

Title:  Battling the underdetermination of dark energy

Abstract: Cosmological data has opened up new vistas on fundamental physics yet it is limited in its scope. While it has given us tantalizing hints at how the Universe might be expanding, it is unclear whether it can ever be used to find the microphysical structure of whatever is driving this expansion. I will discuss the evidence for one proposal, dynamical dark energy driven by a scalar field, pointing out what we can and cannot say about its fundamental nature. I will argue that it is unlikely to be thawing quintessence, that there is strong evidence that there is some type of non-minimal coupling but which brings with it a host of undesirable consequences. I will try to look at the various loopholes and present what I think is the current status of scalar fields as a source of dark energy.

Visitor's room: 123

Visit Schedule:

If you're not meeting in the visitor's office (Room 123), please indicate your office number.

Monday:

• 10:30 a.m.:  (optionally astro-coffee) 

• 11:00 a.m.:  Romain Teyssier (Peyton 134)

• 11:30 a.m.:  (busy)

• 12:00 p.m.: lunch

• 12:30 p.m.:  lunch

• 1:00 p.m.:  

• 1:30 p.m.:

• 2:00 p.m.: Nils Siemonsen

• 2:30 p.m.: 

• 3:00 p.m.: Lucia Perez (Peyton 123)

• 3:30 p.m.: Masa Yamamoto (Peyton 123)

• 4:00 p.m.: 

Wednesday:

• 9:30 a.m.:  

• 10:00 a.m.:  

• 10:30 a.m.:  (optionally astro-coffee) 

• 11:00 a.m.:  

• 11:30 a.m.:  

• 12:00 p.m.: 

• 12:30 p.m.: Wunch

• 1:00 p.m.: Wunch

• 1:30 p.m.: Paul Steinhardt (Jadwin 214)

• 2:00 p.m.: Frans Pretorius (Jadwin 311)

• 2:30 p.m.: Andrew Saydjari (Peyton 132)

• 3:00 p.m.: 

• 3:30 p.m.: Jo Dunkley/group (Jadwin 226)

• 4:00 p.m.: Susanna Azzoni (Jadwin 223)

• 4:30 p.m.: Jo Dunkley/group (Jadwin 226)

Dinner Sign-up - add your name here:

Day of week: Wednesday

1. Faculty Host: Alex Amon

2. Postdoc Host: Masa Yamamoto

3. Caleb Lammers

4. Amir Siraj

5. James Sunseri

6.  Azana Queen

7.  Andrew Saydjari

8.  Speaker

9. Susanna Azzoni (if possible or anyone cancels)

10. April Cheng (if possible or if anyone cancels)

STUDENTS HAVE PRIORITY.

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