Organisers: Liz Helfenberger & Patrick Fritzsch (TCD)
Next Colloquium: 15/10/25 - Antonio Gonzalez-Arroyo (UA Madrid)
Venue: 4 pm, HMI Seminar Room, Hamilton Building (top floor), Trinity College Dublin
Title: The large N limit of gauge theories.
Abstract: I will make a general introduction to the large N limit of gauge theories, including motivation and basic properties. Then I will focus on the property of volume independence leading to defining a strategy based on matrix models. The ingredients needed in understanding the finite N corrections will be explained. This part will be presented as much as possible in a non-technical manner. Next, after presenting the tests performed to ensure the validity of this approach, I will show the results obtained within the last few months/years by me and my collaborators.
2025/26 Colloquium schedule
2025
Sep 17th: David Berenstein (UC Santa Barbara)
Sep 24th: no colloquium
Oct 1st: Roberto Frezzotti (Tor Vergata & INFN)
Oct 8th: Matthew Mccullough (CERN)
Oct 15th: Antonio Gonzalez-Arroyo (UA Madrid)
Oct 22nd: Albrecht Klemm (U Bonn)
Oct 29th: READING WEEK
Nov 5th: Sergey Solodukhin (U Tours)
Nov 12th: Philine van Vliet (LPENS)
Nov 19th: Davide Polvara (U Hamburg)
Nov 26th: Georgios Papathanasiou (Athens U)
Dec 3rd: Sylvain Lacroix (Sorbonne U)
2026
Jan 28th: Shota Komatsu (CERN)
Feb 4th: Volker Schomerus (DESY & U Hamburg)
Feb 11th: Andrzej Pokraka (Amsterdam U)
Feb 18th: Sofia Villecorsa (CERN)
Feb 25th: Matthias Steinhauser (KIT)
Mar 4th: READING WEEK
Mar 11th: Gudrun Hiller (CERN)
Mar 18th: Sean Hartnoll (Cambridge)
Mar 25th: tba
Apr 1st: tba
Apr 8th: tba
PAST EVENTS:
Colloquium: 08/10/25 - Matthew Mccullough (CERN)
Venue: 4 pm, HMI Seminar Room, Hamilton Building (top floor), Trinity College Dublin
Title: Exploring the Boundaries of New Physics: Present and Future.
Abstract: I will discuss the general question of where we might expect new microscopic physics to show up at high energies, considering aspects of motivation versus what is possible from a broader perspective. I will then go on to examine the special role of present and future colliders in exploring and mapping the boundaries of new physics possibilities at high energies.
Colloquium: 01/10/25 - Roberto Frezzotti (Tor Vergata & INFN)
Venue: 4 pm, HMI Seminar Room, Hamilton Building (top floor), Trinity College Dublin
Title: Lattice study of Ds inclusive semileptonic decays -- Inclusive processes from lattice spectral densities.
Abstract: We present the results of a first-principles theoretical study of the inclusive semileptonic decays of the Ds meson. We have performed a state-of-the-art lattice QCD calculation by exploiting recent spectral reconstruction methods and accounting for all sources of systematic errors. We obtained results for the decay rate and lepton moments in agreement with experiment and with a comparable uncertainty. The error is statistically dominated, which allows for further improvement in the future about these observables and/or the extraction of |V_cs|. Our work shows that inclusive semileptonic meson decays can today be studied on the lattice at a phenomenologically relevant level of accuracy and thus paves the way for attacking the semileptonic inclusive decay of B mesons from first principles with the aim to extract e.g. |V_cb| and address the long standing inclusive-vs-exclusive tension. Similar methods can in principle be used to study other inclusive processes on the lattice, ranging from hadronic tau decay to deep inelastic scattering.
Colloquium: 17/09/25 - David Berenstein (UC Santa Barbara)
Venue: 4 pm, HMI Seminar Room, Hamilton Building (top floor), Trinity College Dublin
Title: Goldilocks and the bootstrap.
Abstract: I will describe how to solve certain simplified model problems associated to probability distributions on the infinite line and on a circle with bootstrap methods. The main idea is to show that given a solution, there is a positive definite matrix that can be constructed from the solution. The bootstrap method uses positivity constraints on a finite submatrix of this infinite matrix to find bounds on parameters/values via semidefinite programming. I will explain why this problem converges exponentially fast in the size of the submatrix and in what sense is a finely-tuned problem. For problems on the circle, I will show that with a simple ansatz one can essentially bypass the semidefinite programming part of the problem and obtain a certificate of positivity for an interior point instead. I will apply these methods to the numerical evaluation of orthogonal polynomials for unitary matrix model problems and I will show that numerically the strong coupling phase of the unitary matrix models is very simple, so that there are no 1/N corrections to various quantities.