# Theoretical Cosmology meetings

To actively encourage the field of theoretical cosmology and to set an informal stage for the exchange of ideas, the Dutch theoretical cosmology community organizes Friday afternoon meetings approximately 6 times a year — usually on the first Friday of the month. The meetings typically start in the afternoon with a main speaker, followed by a short break to continue with another seminar or journal club discussion on some topic of current interest. We end the afternoon with drinks. The supporting institutes in Leiden, Amsterdam, Groningen, Utrecht where recently joined by the strings and cosmology group in Leuven and take turns in hosting the event.

- This event has passed.

## Groningen Winter 2017

## January 12 @ 12:00 - 17:00

### Event Navigation

Groningen, January 12th, 2018

The meeting will take place at the Academy building downtown, Broerstraat 5, room A900, which you can find by entering a small building to the left (i.e. west) of the academy building itself, adjacent to the Kilroy store – or ask at the reception of the academy building.

11:45-12:00 Coffee

12:00-13:00 Talk by **Andrew Tolley** (Imperial College)

Title: * Positivity Constraints on Effective Field Theories of Gravity*

__Abstract: __

13:00-14:00 Lunch (not provided)

14:00-15:00 Talk by **Enrico Pajer** (Utrecht University)

Title: * From symmetries to cosmological observables*

__Abstract:__

I will discuss the two main paths from symmetry to cosmological observables: Effective Field Theories (EFT) and Ward-Takahashi identities. First, I will derive the restrictions on the well-known EFT of cosmological backgrounds (a.k.a. the EFT of Inflation) implied by a shift symmetry of the clock. The resulting EFT of shift-symmetric cosmologies describes, among other systems, perfect and imperfect superfluids coupled to gravity and driven superfluids in the decoupling limit. Second, I will derive new Ward-Takahashi identities for the squeezed limit of cosmological correlators using the language of adiabatic modes. I will conclude discussing the yet unexplored class of generalized adiabatic modes that arise from mixing spacetime diffeomorphism with internal symmetries.

15:00-15:30 Coffee

15:30-16:30 Talk by **Daan Meerburg** (Cambridge and Groningen University)

Title: * Cosmological Challenges: Neutrino Mass*

__Abstract:__