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.
- This event has passed.
Amsterdam Summer 2023
07/07/2023 @ 13:00 - 17:00
Amsterdam, July 7th.
13:00 CET: Coffee and tea
13:15-14:15 CET: Talk by Dražen Glavan (CEICO, FZU)
Title: Even photons break de Sitter symmetry
Abstract:
It is commonly held that the propagator for the massless vector field in de Sitter in the general covariant gauge has to respect all the symmetries of the maximally symmetric background. However, this
is precluded by the Ward-Takahashi identity that has gone unnoticed thus far. I will present the recent construction of the photon propagator that satisfies all the conditions of a consistently quantized theory, and that maintains all de Sitter symmetries except spatial special conformal transformations. This propagator vanishes in the infrared, opposed to previously reported solutions to just the propagator equation of motion. Even though the de Sitter breaking pertains to the gauge sector, it is important when interactions are considered. I will discuss the energy-momentum tensor as the simplest one-loop observable to demonstrate further problems arising from failing to account for the Ward-Takahashi identity and the de Sitter breaking it requires.
14:30-15:30 CET: Talk by Adri van Duivenvoorden (Flatiron Institute, New York)
Title: Cosmology with the Atacama Cosmology Telescope
Abstract:
The Atacama Cosmology Telescope (ACT) collaboration is preparing to release the results of a 6-year-long survey covering 40% of the microwave sky at arcminute resolution. The dataset, referred to as DR6, provides a vast jump in sensitivity compared to previous ACT data releases and will deliver some of the strongest constraints on early universe physics, the cosmological parameters and extensions to the Lambda-CDM model. After a brief introduction I will give an overview of the first results of DR6: the recently released CMB lensing papers. I will summarize the novel analysis techniques used for the analysis and discuss implications for the growth of structure. Following that, I will present ACT’s upcoming map of the spectral distortions due to galaxy clusters and end with a short overview of future DR6 results.
15:45-16:45 CET: Talk by Suddhasattwa Brahma (Higgs Centre, University of Edinburgh)
Title: Entanglement Entropy and Complexity in de Sitter
Abstract:
Abstract: Quantum information techniques are playing a crucial role in our understanding of quantum aspects of spacetime. In particular for de Sitter space, I will illustrate this through two different examples. Firstly, I will show why momentum-space entanglement is an essential concept in early universe cosmology, as a quantifier for non-unitary evolution, and derive its conceptual ramifications for quantum corrections to cosmological observables. On the other hand, I will discuss why one needs to go beyond entanglement entropy and explore complexity for the Euclidean vacuum in de Sitter. Finally, I will briefly highlight why this quantum informatic measure is pivotal for establishing cosmic ER=EPR.
17:00 CET: Drinks