## National Seminar Theoretical High Energy Physics

The National Seminar THEP will take place on Friday, March 15 th 2024.

- DATE:
Friday, 15th March 2024

- SPEAKERS:
Jorinde van de Vis (UL)

Gavin Salam (Oxford U)

Andrea Puhm (UvA)

Eric Bergshoeff (RUG)

- ABSTRACTS:
**Jorinde van de Vis (UL) – Gravitational waves from cosmological phase transitions**In many extensions of the Standard Model, the universe underwent one or several first order phase transitions. Such phase transitions proceed via the formation and collision of bubbles. The bubble collisions can source a stochastic gravitational wave background signal. In the case of the electroweak phase transition, the characteristic frequency would fall right in the sensitivity band of LISA. We can thus use data from gravitational wave experiments to probe physics beyond the standard model. In this talk, I will give a brief overview of the relevant contributions to the gravitational wave signal, and then focus on the contribution to the gravitational wave signal from sound waves.

Predictions of the gravitational wave spectrum typically rely on hydrodynamic lattice simulations of the scalar-plasma system. Hydrodynamic solutions of a single expanding bubble provide a bridge between the particle physics model and the hydrodynamic lattice simulation. An important quantity in this computation is the bubble expansion velocity. I will discuss the computation of the bubble wall velocity, and present recent progress in the computation of this quantity, obtained in the limiting cases of local thermal equilibrium and a large enthalpy jump between the two phases.**Gavin Salam (Oxford U) – A Perspective on the Future of High-Energy Physics**

The discovery of the Higgs boson opened the door to the investigation of new fundamental interactions of nature unlike any studied before. After a reminder about how certain essential features of the Higgs mechanism matter for the world around us, this talk will examine (a) what we actually know about the Higgs sector of the Standard Model (much more than we expected to, much less than is written in textbooks); (b) some key questions that could be investigated in the near and more distant futures; and (c) how we might view the wider landscape of high-energy particle physics.**Andrea Puhm (UvA) – Dual descriptions for black holes and the sky**Key to advancing our understanding of quantum gravity in the past quarter century has been the insight that gravitating systems appear to admit dual descriptions of very different nature which can in turn be exploited to study them. Much progress has been made on quantum gravity in asymptotically Anti-de Sitter spacetimes which admit a dual conformal field theory description, and on the microphysics of black holes which are supersymmetric or near-extremal. In this talk I will highlight recent advances that go beyond these limitations. I will report recent progress on formulating a holographic principle for quantum gravity in spacetimes with flat asymptotics which approximate well the physics in our universe below the cosmological scale. Our universe contains rotating black holes which are non-supersymmetric and non-extremal and I will discuss a proposed dual description as fundamental strings which are the basic ingredients of string theory.

**Eric Bergshoeff (RUG)**–**Three-dimensional Massive Gravity and the Fractional Quantum Hall Effect**

In this talk I will compare the massive spin-2 modes that have been observed in the Fractional Quantum Hall effect with the Fierz-Pauli description of massive spin-2 modes in quantum field theory.

Subsequently, I will discuss the generalization to massive higher-spin modes both in the Fractional Quantum Hall effect and quantum field theory. In the final part of the talk I will discuss how new developments in three-dimensional massive gravity could affect the description of massive modes in the Fractional Quantum Hall effect. - LOCATION:
Nikhef colloquium room, Nikhef, Science Park 105, Amsterdam

(A zoom connection is available for those that wish to join remotely: https://go.nikhef.nl/colloquium)

- SCHEDULE:
10:00 Coffee/tea

10:30 Jorinde van de Vis (UL)

11:15 Gavin Salam (Oxford U) –Nikhef colloquium–

12:15 Lunch

14:00 Andrea Puhm (UvA)

14:45 Eric Bergshoeff (RUG)

15:30 Borrel/drinks - LOCAL ORGANIZERS:
For questions or suggestions, please contact one of the organizers:

Wouter Waalewijn (NIKHEF)

e-mail: wouterw@nikhef.nlMarieke Postma (Nikhef)

e-mail: mpostma@nikhef.nlTimothy Budd (RU)

e-mail: T.Budd@science.ru.nl