GGI Tea Break's Seminars

1 Jan 2022, 11:00 → 31 Dec 2022, 13:00 Europe/Rome

It is a new web-seminar series on the Theory of Fundamental interactions, covering a wide spectrum of arguments. The aim is to discuss the open questions in Fundamental Physics while offering to researches and Ph.D. Students a simple introduction to some of the hottest topics in the field. "GGI Tea Breaks" will include Theory Colloquia given by established experts as  well as Focus Meeting on special topics given by two or more scientists with different viewpoints. Ample space for questions and discussion will be allocated at the end of the Seminars.

If you wish to receive announcements please fill the form: https://docs.google.com/forms/d/e/1FAIpQLSezltPaSJJ6SiSSpxVq3H7Dt4AJx0SoKGDbL-8xsKcsFs5fOg/viewform

Wednesday, 19 January

1 GGI Tea Breaks' Special Edition "Steven Weinberg and his legacy"

"The effort to understand the universe is one of the very few things that lifts human life a little above the level of farce, and gives it some of the grace of tragedy." The Galileo Galilei Institute celebrates Steven Weinberg, a founding father of the theory of fundamental interactions and one of the greatest theoretical physicists of the last century. His work has been a source of inspiration and guidance for generations of physicists and is at the heart of current front-line research. This special GGI Tea Breaks'™ event is dedicated to the research of Steven Weinberg, its impact and legacy in theoretical physics. The programme includes four talks, each focused on a particular broad area of research where the work of Weinberg led to breakthrough progress. His contribution will be put into historical context and its relevance for present-day research will be discussed.

Speakers: Riccardo Barbieri (SNS, Pisa), Howard M. Georgi (Harvard University), Edward Witten (IAS Princeton), Nima Arkani-Hamed (IAS Princeton)

Wednesday, 2 February

2 Cosmic Birefringence

Polarised light of the cosmic microwave background, the remnant light of the Big Bang, is sensitive to parity-violating physics. In this presentation we report on new measurements of parity violation, called “cosmic birefringence”, from polarisation data of the European Space Agency (ESA)’s Planck satellite. The statistical significance of the measured signal is about 3 sigma. If confirmed with higher statistical significance in future, it would have profound implications for the elusive nature of dark matter and dark energy.

Speaker: Eiichiro Komatsu (MPI For Astrophysics, Garching)

Wednesday, 9 February

3 Scattering Amplitudes in Maximally Supersymmetric Gauge Theory and a New Duality

Scattering amplitudes are the arena where quantum field theory directly meets collider experiments. An excellent model for scattering in QCD is provided by N=4 super-Yang-Mills theory, particularly in the planar limit of a large number of colors, where the theory becomes integrable, and amplitudes become dual to light-like polygonal Wilson-loop expectation values. The first nontrivial case is the 6-gluon amplitude (hexagonal Wilson loop), which can be computed to 7 loops using a bootstrap which is based on the rigidity of the function space of multiple polylogarithms, together with a few other conditions. It is also possible to bootstrap a particular form factor for the chiral stress-tensor operator to produce 3 gluons, through 8 loops. Remarkably, the two sets of results are related by a mysterious “antipodal” duality, which exchanges the role of branch cuts and derivatives. I will describe how the bootstrapping works and what we know about this new duality.

Speaker: Lance Dixon (SLAC (Stanford University))

Wednesday, 2 March

4 FOCUS MEETING “Challenges and Opportunities of a Muon Collider”

Following the European strategy update, and as a part of the Snowmass studies in the US, high energy muon colliders have received a lot of interest. They have been integrated into the European Accelerator R&D Roadmap. This concept promises to reach very high energies and luminosities because the beam can be accelerated and collided in rings due to the suppression of synchrotron radiation.
On the one hand, the short muon life time, however, poses a number of challenges for the concept, ranging from muon cooling to acceleration, from neutrino radiation to detector design.
On the other hand, recent studies have painted a broad picture of the physics potential of such machines.
In this Focus Meeting, Daniel Schulte (CERN) and Lian-Tao Wang (U. Chicago) will give an overview of the muon collider concept, highlight the associated challenges and review its physics potential.

Speakers: Daniel Schulte ((CERN)), Lian-Tao Wang ((University of Chicago))

Wednesday, 30 March

5 Flavour Physics: Old problems and recent hopes

Flavour physics represents one of the most puzzling aspect of particle physics and, at present, is also one of the most active experimental frontiers. I present a brief introduction to this field, with special emphasis on the subject of Lepton Flavour Universality (LFU).
I review the present hints of LFU violations observed in B decays, discussing their phenomenological interest, and their possible interpretation in terms of physics beyond the Standard Model, both at the EFT level and beyond.

Speaker: Gino Isidori (Univ. of Zurich)

Wednesday, 6 April

6 Berry phases, wormholes and factorization in AdS/CFT

Within the AdS/CFT correspondence, the entanglement properties of the CFT are related to wormholes in the dual gravity theory. This gives rise to questions about the factorisation properties of the Hilbert spaces on both sides of the correspondence. We review these issues and show how
the Berry phase, a geometrical phase encoding information about topology, may be used to reveal similarities between the Hilbert space structure on both sides of the correspondence. Mathematical concepts such as coadjoint orbits play an important role. In addition to its relevance for quantum gravity, this analysis also suggests how to experimentally realise the Berry phase and its relation to entanglement in table-top experiments involving photons or electrons. This provides a
new example for relations between very different branches of physics that follow from the AdS/CFT correspondence and its generalisations.

Speaker: Johanna Erdmenger (University of Würzburg)

Wednesday, 13 April

7 Neutrinos: from surprising past results, to current unexplained anomalies and questions for the future

In the past twenty years, the discovery of neutrino oscillations has changed our understanding of neutrinos and proved that the Standard Model of particle physics is incomplete. We now know that neutrinos have mass and mix. An impressive progress has been made, thanks to a broad experimental programme, and most of their properties have been determined with precision. In this colloquium, I will briefly review the current knowledge of neutrino properties, highlighting the still open questions, with emphasis on the nature of neutrinos, their masses and leptonic CP violation. I will then discuss the hints for a richer structure beyond three-neutrino mixing, which have been interpreted in terms of sterile neutrinos and/or new neutrino interactions. I will review the experimental status and the expected near future developments and their possible theoretical implications.

Speaker: Silvia Pascoli (Università di Bologna)

Wednesday, 27 April

8 Pulling yourself up by your bootstraps in quantum gravity

The bootstrap program leverages symmetry and mathematical consistency to study strongly coupled quantum systems. Its flagship result has been the solution of the 3D critical Ising model from abstract principles alone. In this talk I will outline how universal properties of quantum gravity can also be studied from a bootstrap perspective. A surprising discovery has been a connection between black hole thermodynamics and the sphere packing problem, a venerable question in pure mathematics.

Speaker: Leonardo Rastelli (Yang Institute, Stony Brook)

Wednesday, 11 May

9 Exactly solved models of many-body quantum chaos

I will discuss the problem of unreasonable effectiveness of random matrix theory for description of spectral fluctuations in extended quantum lattice systems. A class of locally interacting spin systems has been recently identified where the spectral form factor is proven to match with gaussian or circular ensembles of random matrix theory, and where spatiotemporal correlation functions of local observables as well as some measures of dynamical complexity can be calculated analytically. These, so-called dual unitary systems, include integrable, non-ergodic, ergodic, and generically, (maximally) chaotic cases. After reviewing the basic results on dual unitary Floquet circuits, I will argue that correlation functions of these models are generally perturbatively stable with respect to breaking dual-unitarity, and describe a simple result within this framework.

Speaker: Tomaz Prosen (University of Ljubljana)

Wednesday, 8 June

10 Why entanglement matters

One century ago Erwin Schrödinger called entanglement "... the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought".
However, only in the last two decades the study of quantum entanglement in many body systems (i.e. field theories) reached such a mature stage to lead to an unprecedented exchange of ideas and concepts between fields that were previously unrelated like quantum information, high-energy physics, statistical mechanics, general relativity, condensed matter and many more.
In this colloquium-style tea break, I will discuss a number of examples taken from different fields in which many-body entanglement is the characteristic physical trait.

Speaker: Pasquale Calabrese (Sissa)

Wednesday, 22 June

11 Bound States in Heavy Dark Sectors: from WIMPonium to Squeezeout

The nature of dark matter remains one of the great puzzles of fundamental physics, with potential connections to a plethora of deep questions. While dark matter is often assumed to be collisionless, dark matter particles may interact with each other through either the known forces of the Standard Model of particle physics, or new "dark" forces, while remaining consistent with current constraints. In either case, dark matter may form bound states similar to those we observe in ordinary matter. I will discuss a range of possible implications of the existence of such bound states, including observational signatures in gamma-ray telescopes, and modifications to the history of the cosmos allowing for strikingly heavy dark matter in strongly-interacting dark sectors.

Speaker: Tracy Slatyer (MIT)