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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Amsterdam Spring 2020

08/05/2020 @ 15:00 - 17:00

Amsterdam, May 8th.

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

Time: May 8, 2020 03:00 PM Amsterdam

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Meeting ID: 939 4974 3367

15:00 – 15:45: Talk by Enrico Pajer (DAMPT, Cambridge)

Title:Boostless Boostrap


The space of inflationary models is vast, containing wide varieties of mechanisms, symmetries, and spectra of particles. Consequently, the space of observational signatures is similarly complex. Hence, it is natural to look for boundaries of the space of models and their signatures.

In the first part of the talk, I’ll prove three theorems about the possible symmetries of cosmological correlators. First, correlation functions of scalar metric fluctuations are uniquely characterized by the soft theorems that generalize Maldacena’s consistency relations and are free from ambiguity under field redefinitions. Second, whatever the particle content and interactions, when the standard soft theorems apply, invariance under de Sitter boosts is only possible if all connected correlators vanish identically, i.e. if the theory is free. Third, conformal invariance is the largest set of linearly realized (bosonic) symmetries of the correlators of any single scalar, irrespectively of any soft theorems or particle content.

In the second part of the talk I’ll discuss some ongoing work on describing cosmological perturbations from “the boundary”, without explicit reference to the time evolution in the “bulk” for popular models of inflation where boost are broken by some condensate.

Link to Recording here.

15:45 – 16:00: Break/Discussion

16:00 – 16:45: Talk by Mustafa Amin (Rice University)

Title: Observables from a Complex Early Universe


Can we tell if the very early universe was simple or complex? What if the early universe was complex — with many fields interacting non-adiabatically with the inflaton during and after inflation? How can we calculate observables if we only have some coarse grained information about the microphysics of such systems? I will present a calculational framework and some general results regarding repeated, non-adiabatic and stochastic particle production in spectator fields, and the resulting curvature perturbations. I will discuss observational implications in the form of nontrivial features, and scale dependence in the curvature power spectrum. The calculational framework is motivated by the phenomenon of current conduction in disordered wires (Anderson Localization), where relatively universal results are obtained independent of the details of the microphysics.

16:45 – 17:00: Final Discussion


15:00 - 17:00
Event Category:


Jan Pieter van der Schaar


Zoom Meeting