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.
Utrecht Spring 2020
June 5 @ 14:00 - 17:00
Utrecht, June 5th.
This meeting will take place via remote connection. Here the information for connecting:
Time: June 5, 2020 02:00 PM Amsterdam
Join Zoom Meeting
Meeting ID: 939 4974 3367
14:00 – 14:30: Talk by Emanuele Castorina (CERN)
Title:Could quasar lensing time delays hint to a core component in halos, instead of H0 tension?
There is a growing tension between measurements of the Hubble parameter H0 based on the classic cosmic distance ladder method and measurements obtained through a fit of the standard ΛCDM model to the CMB or LSS data. Measurements of the time delay between the images of gravitationally lensed objects provide an alternative way to measure H0, and thus far the results of the H0LiCOW collaboration have been in agreement with the distance ladder.
It is therefore of uttermost importance to study all possible systematic effects, both observational and theoretical, that could reconcile the early and late Universe constraints.
In this talk I will focus on a well known systematic uncertainty associated with the choice of the family of models used to reconstruct the lens potential in time delay cosmography. I will show how current measurements of the H0LiCOW collaboration do not allow to distinguish between the most widely used lens profiles and an entire class of models which exhibit a subdominant core component. The latter would return a value of H0 in agreement with the CMB and LSS.
I will show how external datasets, like stellar kinematics, do not exclude the presence of a inner core. Finally I will speculate on what kind of dark matter models could generate such a core.
14:45 – 15:15: Talk by Drazen Glavan (UCLouvain)
Title: Loop corrections to E&M fluctuations in inflation
Vector fields are insensitive to the rapid expansion of the primordial inflating universe due to the conformal coupling to gravity. However, they may couple to other light fields that are sensitive to the expansion and experience huge gravitational particle production, such as the complex scalar. In that case the vector field can develop large electric and magnetic field fluctuations induced by the gravitationally enhanced charge fluctuations. I will present a computation of the one-loop corrections to the electric and magnetic field correlators of SQED in power-law inflation. One-loop corrections show secular enhancement and spatial running at superhorizon separations, and easily dwarf the tree-level contributions. The correlators satisfy a hierarchy due to Faraday’s law in inflation, which dictates that electric fields are always larger than magnetic ones.
15:30 – 16:00: Talk by Macarena Lagos (KICP – University of Chicago)
Title: Testing dark energy with standard sirens
As we enter the era of precision cosmology, the behavior of gravity on large scales and the nature of the main constituents of the universe still remain debatable. Future data from the Cosmic Microwave Background and galaxy surveys, along with the advent of gravitational waves (GW) will provide us precise constraints that will help uncover some cosmological puzzles. In this talk, I will focus on testing the nature of dark energy with GW. In particular, I will argue that in the LCDM there is a universal gravitational coupling —given by Newton’s gravitational constant— but if dark energy is dynamical then it can induce a time evolution in the gravitational coupling, which can be tested with direct GW detections. I will discuss some forecasts for LIGO, and mention how these observations will complement present constraints on time-varying gravitational couplings from cosmology and solar system observations.
16:00 – 16:45: Virtual Borrel