List of talks

Ukraine Seminar in Fundamental Physics

1. Connecting quantum gravity and particle physics: why and how?

Prof. Astrid Eichhorn (Centre for Cosmology and Particle Physics Phenomenology, University of Southern Denmark, Odense, Denmark)

March 23, 2023, 4pm CET (3pm GMT, 5pm EET, 10 am EST)

Abstract: Proposals for quantum gravity theories must be tested by confronting them with observational data. I will argue that this is achievable by exploring the interplay of quantum gravity with matter, both in and beyond the Standard Model. At the same time, the interplay with quantum gravity may provide us with explanations for some of the mysteries of particle physics. For instance, free parameters of the Standard Model may become calculable from first principles in a quantum theory of gravity and matter. As a second example, the vast space of phenomenological models for dark matter may be reduced to just a small handful of possibilities, giving us insight into the nature of dark matter. To illustrate these ideas, I will introduce the theory of asymptotically safe quantum gravity with matter and review evidence that it could have explanatory power in and beyond the Standard Model.

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2.Cosmology as a probe of fundamental physics

Prof. Tamara Davis (School of Mathematics and Physics, The University of Queensland, Brisbane, Australia)

April 27, 2023, 4pm CEST (3pm BST, 5pm EEST, 10 am EDT, midnight April 28 EAST)

Abstract: The last few decades have been a golden age for observational astrophysics and cosmology, with the power of modern telescopes revealing surprising features of our Universe in ever more detail.  From explaining the mysteries of dark matter and dark energy, to measuring the mass of the neutrino and understanding nuclear physics through gravitational waves, modern astrophysics is now a key tool in studying fundamental physics.  In this talk Tamara Davis will summarize the main methods by which astrophysicists are pushing the boundaries of known physics, and discuss the cracks (“tensions”) that are emerging between different cosmological probes.

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3. Searching for high-frequency GWs with axion haloscopes

Dr. Valerie Domcke (CERN, Geneva, Switzerland)

May 27, 2023, 5pm CEST (4pm BST, 6pm EEST, 11 am EDT)

Abstract: Gravitational waves (GWs) generate oscillating electromagnetic effects in the vicinity of external electric and magnetic fields. I will discuss this phenomenon with a particular focus on reinterpreting the results of axion haloscopes based on lumped-element LC circuits, which probe GWs in the 100 kHz–100 MHz range. Measurements from ABRACADABRA and SHAFT already place bounds on GWs, although the present strain sensitivity is weak. However, the sensitivity scaling with the volume of such instruments is significant—faster than for axions—and so rapid progress will be made in the future. I will discuss opportunities at future facilities with a focus on the DMRadio program.

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4. Probing New Physics at the Pulsar Timing Array Frontier

Prof. Dr. Kai Schmitz (University of Münster, Münster, Germany), NANOGrav Collaboration November 23, 2023, 4pm CET (3pm GMT, 5pm EET, 10am EST)

Abstract:Pulsar Timing Array (PTA) collaborations around the globe recently announced compelling evidence for low-frequency gravitational waves permeating our entire Universe, that is, a gravitational-wave background (GWB) reaching us from all directions and at all times. This breakthrough achievement has important implications for astrophysics, as the GWB signal, if genuine, is likely to originate from a cosmic population of supermassive black holes orbiting each other at the centers of galaxies. As I will illustrate in this talk, the new PTA data is, however, also of great interest to the high-energy physics community, as it allows us to probe a broad range of particle physics models of the early Universe that predict the generation of a cosmological GWB in the Big Bang. In this sense, the PTA data opens a new window onto the very early Universe and enables particle physicists to constrain scenarios of new physics beyond the Standard Model at extremely high energies. In my talk, I will give an overview of these searches for new physics at the PTA frontier and highlight several cosmological scenarios that underline the relevance of PTA observations for fundamental problems such as dark matter, neutrino masses, and the matter-antimatter asymmetry of the Universe. Finally, I will conclude with a brief outlook on future measurements that may help in discriminating between a GWB signal of astrophysical origin and a GWB signal from the Big Bang.

See on YouTube: to be announced