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.

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Groningen Spring 2021

May 7 @ 14:30 - 17:00

Groningen, May 7th.

This meeting will take place via remote connection. Here the information for connecting:

Time: May 7, 2021 02:30 PM Amsterdam Time

Join Zoom Meeting
Zoom Link
Meeting ID: 890 4133 2437
Password: 506154

14:30-15:10 CET: Talk by David Stefanyszyn (DAMTP)

Title: From locality and unitarity to cosmological correlators


The on-shell approach to computing scattering amplitudes has lead to tremendous progress in particle physics. The combination of symmetries, locality and unitarity allows one to efficiently explore the space of consistent effective theories of massless particles without using Lagrangians or introducing gauge redundancies. Effort has recently turned to applying a similar logic to “bootstrap” the fundamental observables in cosmology, namely cosmological correlators that live on the late-time boundary of an approximately de-Sitter spacetime. After outlining the success of the on-shell approach for particle physics, I will explain how we can efficiently bootstrap three and four point functions in the effective field theory of inflation by using a small number of physical principles.

15:15-15:55 CET: Talk by Gonzalo Palma (Chile University)

Title: Seeding primordial black holes in multifield inflation 


The inflationary origin of primordial black holes (PBHs) relies on a large enhancement of the power spectrum of the primordial curvature fluctuation ζ at wavelengths much shorter than those relevant for CMB anisotropies. This is typically achieved in models where ζ evolves without interacting significantly with additional scalar degrees of freedom. However, quantum gravity inspired models are characterized by moduli spaces with highly curved geometries and a large number of scalar fields that could vigorously interact with ζ. In this talk I will discuss how isocurvature fluctuations can mix with ζ inducing large enhancements of its amplitude. This occurs whenever the inflationary trajectory experiences rapid turns in the field space of the model leading to amplifications that are exponentially sensitive to the total angle swept by the turn, which induce characteristic observable signatures on the power spectrum of ζ. I will also discuss other characteristic signatures, such as the generation of gravity waves.

16:00-16:40 CET: Talk by Katelin Schutz (MIT)

Title: Making dark matter out of light: the cosmology of sub-MeV freeze-in


Dark matter could be a “thermal-ish” relic of freeze-in, where the dark matter is produced by extremely feeble interactions with Standard Model particles dominantly at low temperatures. In this talk, I will discuss how sub-MeV dark matter can be made through freeze-in, accounting for a dominant channel where the dark matter gets produced by the decay of plasmons (photons that have an in-medium mass in the primordial plasma of our Universe). I will also explain how the resulting non-thermal dark matter velocity distribution can impact cosmological observables.

16:45 CET: social virtual borrel and socializing


May 7
14:30 - 17:00
Event Category:


Daan Meerburg
Giorgio Orlando