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 Winter 2022
March 4 @ 13:30 - 17:00
Groningen, March 4th.
This meeting will take place in an hybrid format. Here the information for connecting:
Time: March 4th, 2022 01:30 PM Amsterdam Time
Join Zoom Meeting
Meeting ID: 814 0629 4208
13:30-14:30 CET: Talk by Sam Young (Leiden University)
Title: Primordial black holes in the early and late Universe
Primordial black holes (PBHs) are a hypothetical form of black hole (BH)
which may have formed from the collapse of large density perturbations
in the very early universe. Not only are they a viable and appealing
dark matter candidate, but they also provide a unique probe to study the
small-scale physics of the early universe, as well as potentially being
the progenitors for the merging binary BH systems observed by
LIGO/Virgo. To determine the validity of such models and derive accurate
constraints, we need a good understanding of how, when and where PBHs
form, and how this can depend on primordial non-Gaussianities and phase
transitions in the early universe. In this talk I will discuss the
motivation to study PBHs and their formation, before discussing recent
developments in the field for which I have made contributions. I will
focus on effects important for determining the merger rate of binary
PBHs observable today, include the effect of non-Gaussianities on the
abundance, mass and initial clustering of PBHs, as well as the
interactions of binary PBHs with nearby objects. This will be crucial in
determining whether the progenitor BHs of the LIGO/Virgo binaries are
primordial or astrophysical in origin.
14:30-14:45 CET: Break
14:45-15:45 CET: Talk by Marko Simonovic (CERN)
Title: Constraints on single-field inflation from the BOSS galaxy survey
The last decade has seen a large improvement in theoretical understanding of galaxy clustering on cosmological scales. The culmination of this program was recent CMB-independent measurement of cosmological parameters and optimal analysis of galaxy bispectrum which led to the first constraints on equilateral and orthogonal non-Gaussianity from spectroscopic galaxy surveys. In this talk I will review the main theoretical and practical developments which led to this progress, with the particular focus on primordial non-Gaussianity. I will also highlight the main lessons we learned so far and discuss further steps that have to be made in order to optimally extract information from the ongoing galaxy surveys such as DESI and Euclid.
15:45-16:00 CET: Break
16:00-17:00 CET: Talk by Vanessa Böhm (Berkeley University)
Title: Fast, accurate and differentiable simulations of weak cosmic lensing
Upcoming experiments such as the LSST survey (Vera Rubin Observatory) or the EUCLID satellite will probe the weak cosmic shear signal far into the non-gaussian regime. These new datasets mark the end of an era in which power spectra analyses and linear models were close to optimal for extracting cosmological information from weak lensing data. New datasets require non-linear models and inference schemes that can accurately extract information from non-Gaussian signals. In my talk I will explore new avenues for weak gravitational lensing analysis and argue that they all rely on fast and differentiable data models. I will show how automatic differentiation which lies at the heart of deep neural networks can be exploited to develop differentiable N-body simulations and present MADLens, a fully differentiable weak gravitational lensing simulator that produces non-Gaussian convergence maps at unprecedented accuracy and low computational cost.
17:00 CET: Borrel