The University of Southampton

- Event

Date:
28th of April, 2023  @  13:00 - 14:15
Venue:
46/5081 and on Teams

Event details

​Floccinihilipilification is defined by the Oxford English dictionary as "the action or habit of estimating something as worthless".
By cutting away worthless new physics models, we are left with a list of possibly valuable ones. To this end, we first describe a bottom-up list of all anomaly-free semi-simple gauge extensions of the Standard Model whose fermionic content is that of the Standard Model plus three right-handed neutrinos. Secondly, we discuss the B3-L2 Z' solution to b->s l+ l- anomalies, and whether or not recent LHCb data has rendered it worthless.

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- Event

Date:
17th of March, 2023  @  13:00 - 14:15
Venue:
46/5081 and on Teams

Event details

In this talk, I will discuss the importance of precisely constraining various anomalous couplings in the electroweak sector from an Effective Field Theory (EFT) standpoint upon considering various di-boson and Higgs-strahlung processes. I will emphasise the importance of considering higher order corrections in perturbation theory in obtaining such constraints. The importance of matching UV-complete models with EFTs will be discussed. Finally, I will shift gears and try to impress upon the audience the need for higher-order corrections in perturbation theory in physics beyond the Standard Model of particle physics. I will specifically focus on the importance of considering next-to-leading order electroweak corrections in the relic abundance calculations for an extended Higgs model.

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- Event

Date:
23rd of March, 2023  @  13:00 - 14:00
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- Event

Date:
24th of March, 2023  @  13:00 - 14:15
Venue:
46/5081 and on Teams

Event details

​Quantum gravity is undoubtfully one of the most important missing pieces in the understanding of the mathematical structure of our universe.

The impossibility of consistently quantizing gravity via perturbative quantum field theory has led to a plethora of different proposals, from asymptotically safe gravity to non-local gravity, loop quantum gravity, and string theory. Different approaches face different problems and have succeeded in different areas. Yet, on the conceptual side, it is not obvious that all these frameworks are inequivalent or unrelated: some theories may be low-energy approximations of others, or could even provide different mathematical descriptions of the same physics. On the technical side, the knowledge gained in an approach could be useful to investigate certain aspects of others.

In this spirit, I will review progress in connecting and contrasting two theories: asymptotically safe gravity and string theory. Specifically, I will discuss how to test asymptotic safety using stringy swampland constraints, and how techniques developed in the context of asymptotically safe gravity can be exploited to compute cosmological higher-derivative corrections to all orders in string theory.

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- Event

Date:
3rd of March, 2023  @  13:00 - 14:15
Venue:
46/5081 and on Teams

Event details

​Numerical lattice calculations provide a powerful method for systematically estimating finite-volume Euclidean correlators. To connect to physical observables, one must analyze the role of the Euclidean signature and finite volume, as well as other systematic effects. In this seminar, I will review work on interpreting multi-hadron observables as spectral functions, given by inverting the Laplace transform on a particular lattice correlator. I will describe methods for regulating this notoriously ill-posed problem by targeting a smeared spectral function. This “smearing" turns out to be of great physical importance, e.g. for defining the infinite-volume limit and for implementing the required i-epsilon pole prescription. I will further discuss how this can be understood as an extension of the famous work of Maiani and Testa on Euclidean correlators. These methods are expected to be most relevant in quantities with many hadronic intermediate states including long distance contributions to heavy meson mixing and decays.

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- Event

Date:
2nd of March, 2023  @  13:00 - 14:00
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- Event

Date:
4th of May, 2023  @  13:00 - 14:00
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- Event

Date:
24th of February, 2023  @  13:00 - 14:15
Venue:
46/5081 and on Teams

Event details

We consider the effective theory of perturbative quantum gravity coupled to a point particle, quantizing fluctuations of both the gravitational field and the particle's position around flat space. Using a recent relational approach to construct gauge-invariant observables, we compute one-loop graviton corrections to the invariant metric perturbation, whose time-time component gives the Newtonian gravitational potential. The resulting quantum correction consists of two parts: the first stems from graviton loops and agrees with the correction derived by other methods, while the second one is sourced by the quantum fluctuations of the particle's position and energy-momentum, and may be viewed as an analog of a ``Zitterbewegung''. As a check on the computation, we also recover classical corrections which agree with the perturbative expansion of the Schwarzschild metric. Based on joint work with C. Rein and R. Verch, arXiv:2109.09753 [JHEP 01 (2022) 180].
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- Event

Date:
17th of February, 2023  @  13:00 - 14:15
Venue:
Microsoft Teams

Event details

Lepton asymmetries present in the early universe can source helical hypermagnetic fields through the chiral plasma instability. If these hypermagnetic fields survive until the electroweak phase transition, they source a contribution to the baryon asymmetry of the universe. In this talk I will explain how this phenomenon can, one the one hand, be used to set the to date strongest bounds on primordial lepton flavour asymmetries and on the other hand, can play a key role in viable baryogenesis models.

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- Event

Date:
3rd of February, 2023  @  15:00 - 16:15
Venue:
Microsoft Teams

Event details

Whether neutrinos are Majorana or Dirac particles is an open question. Theoretically, it is also possible that neutrinos are pseudo-Dirac, which are fundamentally Majorana fermions, but essentially act like Dirac fermions in most experimental settings due to extremely small active-sterile mass splitting. However, they can be differentiated through active-sterile oscillations with an astrophysical baseline. In this talk, we will show that the recent identification of ultra-high energy neutrino sources by the IceCube Neutrino Observatory provides us with such an astrophysical baseline, thus improving the reach of terrestrial experiments by more than a billion for the mass-squared difference.

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