Format of the Journal club

1) PGR seminar, usually about own work (30 min + questions)
2) OPTIONAL: Deep dive into a recent paper (30 min incl. questions and discussion)
3) arxiv Discussion. Please add these papers to this list.  

Schedule

Semester 1 

24/09/25 - 54 / 5025 (5B) (TBC) - Organizational group meeting

01/10/25 - 54 / 7035 (7B) - Rowan Wright (External speaker)

08/10/25 - 54 / 7035 (7B) - No Journal club (Maths Forum)

15/10/25 - 54 / 7035 (7B) - Radu Moga + arxiv discussion

22/10/25 - STAG Lecture - No Journal club

29/10/25 - 54 / 7035 (7B) - Orestis Papadopoulos + Deep dive (Javier Carballo) + short arxiv discussion

05/11/25 - 54 / 7035 (7B) - Dongsheng Ge (External speaker)

12/11/25 - 06 / 1083 - Ayngaran Thavanesan (External speaker)

19/11/25 - 06 / 1083 - Andrea Conti (External speaker)

26/11/25 - 06 / 1083 - Altay Etkin

03/12/25 - Location TBC - Tommaso Pedroni (External speaker)

10/12/25 - 54 / 7035 (7B) - Alex Ratcliffe

17/12/25 - 54 / 7035 (7B) - Arvind Shekar

[Winter break: 14 Dec 2025 - 4 Jan 2026]

[Exam period: 12-23 Jan 2026]

Semester 2 

28/01/26 - Javier Carballo

04/02/26 -  David Sola Gil

11/02/26 - Daniel Baig

18/02/26 - Giorgio Belleri

25/02/26 - James Ratcliffe

04/03/26 - Chen Huang

11/03/26 - Jan Becker

18/03/26 - Elisa Marieni

[Spring break: 22 March 2026 through 19 April 2026]

22/04/26 - 

29/04/26 - 

06/05/26 - 

13/05/26 - 

[Exam period 18 May 2026 - 6 June 2026]

Titles and Abstracts (reverse chronological order):

Dongsheng Ge (External speaker): How to get an interacting conformal line defect for free theories

Abstract: In this talk, I will argue that interacting conformal line defects in free quantum field theories can exist, provided that inversion symmetry is broken. Important for our demonstration is the existence of a special cross ratio for bulk-defect-defect three point functions that is invariant under the conformal group but picks up a sign under inversion. We examine the particular case of a free scalar field in detail, and provide a toy model example where this bulk field interacts via a Yukawa term with fermions on the line. We expect nontrivial line defects may also exist for free Maxwell theory in four dimensions and free bulk fermions. This talk is based on a recent work (2510.02871) with Chris Herzog and Sam Bartlett-Tisdall.

PGR Seminar Speaker: Orestis Papadopoulos
Title: Softening holographic nuclear matter

Abstract: The description of strongly interacting matter at large chemical potentials and/or temperatures is a difficult task. The AdS/CFT correspondence can provide insight into this regime. I will use a particular top-down construction, the Witten-Sakai-Sugimoto model, to describe nuclear matter at finite densities. Within this model, baryons can be described as instantonic solutions of a gauge theory living on D8 flavor branes in the bulk. At higher densities, multiple instantons can be approximated by a spatially homogeneous ansatz, with a topological baryon number being introduced via a discontinuity in the non abelian sector, along the holographic direction. I will present results of solutions with up to 4 discontinuities, which I check systematically, showcasing a new ground state, while also making the nuclear matter more realistic with a reduced incompressibility. I will also point out a connection between the homogeneous ansatz and pointlike instantons.

PGR Seminar Speaker: Rowan Wright

Title: Correlation functions of multiple light-like Wilson loops in maximally supersymmetric Yang-Mills theory

Abstract: Planar scattering amplitudes in N=4 Super Yang-Mills theory are famously dual to the expectation values of null polygonal Wilson loops. I will present ongoing work which shows that much of the same mathematical structure is also enjoyed by correlators of multiple light-like Wilson loops, such as a BCFW-like recursion relation and a simple generalisation of the Q-bar equation. I will also present a derivation of the leading singularities of one-loop scattering amplitudes/Wilson loops into products of tree level amplitudes from the perspective of twistor Wilson loop diagrams, and sketch out how the same procedure allows the one-loop leading singularities of multiple light-like Wilson loop correlators to be expressed in a similarly compact form.