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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Leiden Fall 2019

November 8 @ 13:00 - 17:30

Leiden,  November 8th.

The meeting will take place in Leiden, at the Institute Lorentz for Theoretical Physics, Niels Bohrweg 2, Leiden in room Oort 276.

13:00 – 14:00: Talk by David Harvey (Institute Lorentz)

Title:Testing dark matter self-interactions with future all-sky surveys


Probing the interactions of dark matter provides a pathway to understanding its nature, however in the absence of any detection, we are being forced to diversify our search and look beyond the usual coupling between dark matter and the Standard Model of Particle Physics.
In the currently accepted cosmological model, dark matter is assumed to be collisionless, yet the self-interaction cross-section actually remains relatively unconstrained, with viable models able to modify the structure of galaxies and clusters of galaxies on an observable scale. In this talk I will present the cosmological manifestations of a finite self-interaction cross-section, what are the main hurdles we face in constraining this and how the advent of all-sky telescopes such as LSST and Euclid will revolutionise our view of the dark sector.

14:00 – 14:30: Coffee Break

14:30 – 15:30: Talk by Miguel Zumalacarregui(UC Berkeley & IPhT Saclay)

Title: No LIGO MACHO: bounds on primordial black holes as dark matter from gravitational lensing of supernovae


Black hole mergers detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) have revived dark matter models based on primordial black holes (PBH) or other massive compact halo objects (MACHO). These objects would be abundant in the mass range 1-100 M_Sun, where rather remarkably, previous bounds were the weakest. I will present constraints on the PBH abundance and mass using the gravitational lensing magnification of type Ia supernovae using current data. Our results rule out the hypothesis of MACHO/PBH comprising the totality of the dark matter at high significance in the mass range M > 0.01 M_Sun. Eliminating the possibility of a LIGO-mass MACHO constraints early-universe models that produce PBHs and further strengthens the case for lighter dark matter candidates.

15:30 – 16:30: Talk by Alexander Westphal(DESY)

Title: Flattened Axion Monodromy Beyond Two Derivatives


We study string inspired two-field models of large-field inflation based on axion monodromy in the presence of an interacting heavier modulus. This class of models has enough structure to approximate at least part of the backreaction effects known in full string theory, such as kinetic mixing with the axion, and flattening of the scalar potential. Yet, it is simple enough to fully describe the structure of higher-point curvature perturbation interactions driven by the adjusting modulus backreaction dynamics. We find that the presence of the heavy modulus can be described via two equivalent effective field theories, both of which can incorporate reductions of the speed of sound. Hence, the presence of heavier moduli in axion monodromy inflation constructions will necessarily generate some amount of non-Gaussianity accompanied by changes to n_s and r beyond what results from just from the well known adiabatic flattening backreaction.

16:30 – 17:30: Borrel


November 8
13:00 - 17:30
Event Category:


Ana Achucarro


Institute Lorentz Leiden
Niels Bohrweg 2
Leiden, 2333 CA Netherlands
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