Theory Seminar

The seminar of the Theory Section takes place Fridays in E3-128 and on zoom, starting normally at 12.15

09.10.2020, David Mota (UiO): Cosmological and Astrophysical probes of Gravity Theories beyond General Relativity
Abstract: Several modifications to general relativity have been proposed with the aim to explain the nature of dark energy and the accelerated expansion of the Universe. In this talk I will review the present status of modified theories of gravity in the light of astrophysical probes of gravity in the weak-field regime, ranging from stars to cosmological scales. I begin by setting the scene for how theories beyond General Relativity are expected to behave in the different astrophysical systems, as well as their cosmological signatures. With these in hand, I present a range of observational tests with an eye to using the current and next generation of observations for tests of gravity. In particular, I will show how physical observables of the non-linear regime of structure formation are promising probes to constraining theoretical models in the nonlinear dynamics of stars, galaxies, clusters and large scale structure.

23.10.2020, Tim Linden (Stockholm U/OKC): Thermal WIMPs on the Brink
Abstract: Weakly Interacting Dark Matter Particles (WIMPs) are among the most well-motivated models for particle dark matter. While these particles can be detected through direct, indirect, or collider experiments, only their indirect annihilation produces a guaranteed signal. Intriguingly, experimental searches using both gamma-rays and cosmic-rays are beginning to close in on this coveted "thermal annihilation cross-section". Intriguingly, several excesses in Galactic center gamma-rays and cosmic-ray antiprotons have been discovered. Even more intriguingly, these excesses may be consistent with each other. In this talk, I will summarize the current state of the field, and argue that there is hope of resolving this puzzle within the next five years.

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