# Upcoming seminars

01/08/2019, 16:00 **Andrei Frolov, **Cosmic dust is everywhere

12/08/2019, 14:00 **Camilo Garcia-Cely, **Self-interacting Spin-2 Dark Matter

30/09/2019, 14:00 **Antoine Bourget, **TBA

01/10/2019, 14:00 **Poulami Nandi, **Field Theories with Conformal Carrollian Symmetry

10/10/2019, 14:00 **Cosimo Bambi, **TBA

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**01/08/2019 -- Andrei Frolov (Simon Fraser University)**

Time: 16:00

Place: 226

The simple story of primordial gravitational waves produced by inflation sourcing B-modes of Cosmic Microwave Background polarization in reality is complicated by the fact that we are looking through the coloured glass of astrophysical foregrounds originating much closer to home. I will talk about amplitude of primordial B-modes we expect from inflation, characterization of polarized dust foregrounds from Planck Legacy data, and where do we go from here. In particular, I will show new reconstruction of the large-scale galactic magnetic field responsible for the patterns we see in the dust polarization, and explain how it allows accurate modelling of the polarized dust emission for design and analysis of future CMB experiments.** **

**12/08/2019 -- Camilo Garcia-Cely (DESY, Hamburg)**

Time: 14:00

Place: 226

In this talk, I will discuss MeV spin-2 dark matter. In particular, I will show that such a particle typically self-interacts and undergoes self-annihilations via 3-to-2 processes. I will discuss its production mechanisms and also identify the regions of the parameter space where self-interactions can alleviate the discrepancies at small scales between the predictions of the collisionless dark matter paradigm and cosmological N-body simulations.** **

**01/10/2019 -- Poulami Nandi ()**

Time: 14:00

Place: 117

Conformal Carrollian groups are known to be isomorphic to Bondi-Metzner-Sachs (BMS) groups that arise as the asymptotic symmetries at the null boundary of Minkowski spacetime. The Carrollian algebra is obtained from the Poincare algebra by taking the speed of light to zero, and the conformal version similarly follows. In this paper, we construct explicit examples of Conformal Carrollian field theories as limits of relativistic conformal theories, which include Carrollian versions of scalars, fermions, electromagnetism, Yang-Mills theory and general gauge theories coupled to matter fields. Due to the isomorphism with BMS symmetries, these field theories form prototypical examples of holographic duals to gravitational theories in asymptotically flat spacetimes. The intricacies of the limiting procedure lead to a plethora of different Carrollian sectors in the gauge theories we consider. Concentrating on the equations of motion of these theories, we show that even in dimensions d = 4, there is an infinite enhancement of the underlying symmetry structure. Our analysis is general enough to suggest that this infinite enhancement is a generic feature of the ultra-relativistic limit that we consider.