Speaker: Sam Homiller
Title: Zero Modes of Massive Fermions and Axion Strings
Room: 3024
Host: John Terning
Abstract: Axion strings have been the subject of a renewed interest in recent years, both as fundamental objects in higher-dimensional gauge theories, and as topological solitons that can play an important phenomenological role in Cosmology. It is well known that massless chiral excitations can arise between a fermion and an axion string, propagating along the string and allowing it to superconduct. The properties of these excitations, or zero modes, dictate how the string interacts with light and can thus have important phenomenological consequences. In this talk, I’ll revisit the story of these zero modes, and discuss how this story changes when a nowhere-vanishing Dirac mass for the fermion is added to the usual low-energy theory of axion electrodynamics. Using analytic, numerical and theoretical arguments, I will show that the zero modes exhibit an interesting phase structure, in which they delocalize from the string core as the mass increases, up until a critical value past which they disappear.
User:
High-Energy Seminars
Time:
1:30pm - 3:00pm
Send Reminder:
Yes - 0 days 6 hour 0 minutes before start
Description:
Speaker: Andrew Liddle
Title: Interpreting DESI's evidence for evolving dark energy
Room: 3024
Host: John Terning
Abstract: We are all bored with LambdaCDM and seeking new cosmological physics to explore. For a decade the Hubble tension has been motivating vast numbers of new physics proposals, while this year the DESI collaboration claimed `tantalising hints’ of dark energy evolution from combined cosmic microwave background, baryon acoustic oscillation, and supernova data. We analyse both these lines of evidence from a Bayesian perspective. We argue that reduced tension alone cannot be used a robust signature of new physics, and that the best-fit evolving dark energy models create a new form of cosmic coincidence. In each case careful assessment of model and parameter priors is crucial, and models capable of fitting the data appear a priori unlikely.
User:
High-Energy Seminars
Time:
1:30pm - 3:00pm
Send Reminder:
Yes - 0 days 6 hour 0 minutes before start
Description:
Speaker: Hsing-Yi Lai
Title: Phenomenlogy of Dark Monopoles
Room: 3024
Host: John Terning
Abstract: Dark magnetic monopole not only acts as a dark matter candidate but also gives important insights to the monopole problem. In this talk I will give an overview of the phenomenology on dark magnetic monopole, specifically its total cross-section at the LHC. I will also talk about how the spinor helicity techniques developed in the recent amplitude program can shed light on this topic.
Cinco de Mayo