Journal Club
The target group of the Theoretical Physics Journal Club are PhD students and postdocs doing research on different topics of theoretical physics. Here we can meet to learn and discuss classical or new topics of theoretical physics.
Organizer: Giulia Fardelli (giulia.fardelli@physics.uu.se)
Talks - Fall 2023
Fun with E_{7+1/2}
Speaker: Kaiwen Sun
Papers:
- On intermediate Lie algebra E_{7+1/2} 2306.09230
Date: 15 September 2023, 1.45pm
Location: Å92110
Talks - Spring 2023
An exact solution to cosmological bootstrap
Speaker: Sourav Sarkar
Papers:
- A constructive solution to the cosmological bootstrap 2305.08939
Date: 26 May 2023, 1.30pm
Location: Å80121
Non-Invertible Global Symmetries in the Standard Model
Speaker: Roman Mauch
Papers:
- Non-invertible Global Symmetries in the Standard Model 2205.05086
Date: 12 May 2023, 1.30pm
Location: Å80121
Symmetry fractionalization, 't Hooft anomalies, and line operators
Speaker: Vladimir Bashmakov
Papers:
- Line Defect Quantum Numbers & Anomalies 2206.15401
- Anomalies and Symmetry Fractionalization 2206.15118
Date: 05 May 2023, 1.30pm
Location: Å80121
M-theory geometric engineering for 5d SCFTs: from rank 0 to "conformal matter" theories
Speaker: Andrea Sangiovanni
Abstract: We explore a novel technique to characterize the Higgs branch of rank 0 5d SCFTs from M-theory on non-compact Calabi-Yau threefolds. Building on this result, we propose higher-rank genuine "conformal matter" SCFTs in five dimensions.
Date: 28 April 2023, 1.30pm
Location: Å80121
Witten's iɛ for the string in practice: Convergent expansions for one-loop string amplitudes
Speaker: Carlos Rodriguez Fernandez
Abstract: String amplitudes are often expressed as asymptotic expansions defined on unphysical kinematics, and the exercise of analytically continuing these to physical kinematics is often left to the reader. In their work [2302.12733], Sebastian Mizera and Lorenz Eberhardt apply Witten's iɛ prescription [1307.5124] and achieve a convergent expansion of 4-point open string amplitudes in a physical region.
Papers:
- Evaluating one-loop string amplitudes 2302.12733
- The Feynman iε in String Theory 1307.5124
Date: 21 April 2023, 1.30pm
Location: Å80121
QCD strings
Speaker: Maor Ben-Shahar
Papers:
- Effective String Theory Revisited 1203.1054
- Towards a Theory of the QCD String 1511.01908
- 3D Yang-Mills Glueballs vs Closed Effective Strings 2104.02154
Date: 14 April 2023, 1.30pm
Location: Å80121
Heterotic strings in ALE spaces
Speaker: Muyang Liu
Papers:
- Back to Heterotic Strings on ALE Spaces: Part I -- Geometry of T-dual Little Strings 2209.10551
- Back to Heterotic Strings on ALE Spaces: Part II -- Geometry of T-dual Little Strings 2212.05311
- 6D Heterotic Little String Theories and F-theory Geometry: An Introduction 2303.13502
Date: 31 March 2023, 1.30pm
Location: Å80121
How to get rich
Speaker: Daniel Panizo
Abstract: pdf
Date: 17 March 2023, 1.30pm
Location: Å80121
Black hole microstate counting from the gravitational path integral
Speaker: Charles Thull
Papers:
- Black hole microstate counting from the gravitational path integral 2209.13602
Date: 10 March 2023, 1.30pm
Location: Å80121
Non-invertible Gauss Law and Axions
Speaker: Azeem Hasan
Papers:
- Non-invertible Gauss Law and Axions 2212.04499
Date: 03 March 2023, 1.30pm
Location: Å80121
Bananas of equal mass: any loop, any order in the dimensional regularisation parameter
Speaker: Yoann Sohnle
Papers:
- Bananas of equal mass: any loop, any order in the dimensional regularisation parameter 2212.08908
Date: 24 February 2023, 1.30pm
Location: Å80121
11D Pure spinor physical operators and the b-ghost
Speaker: Max Guillen
Papers:
- Taming the 11D pure spinor b-ghost 2212.13653
Date: 17 February 2023, 1.30pm
Location: Å80127
Scattering in black hole backgrounds and higher-spin amplitudes
Speaker: Kays Haddad
Papers:
- Scattering in black hole backgrounds and higher-spin amplitudes 2212.07965
Date: 10 February 2023, 1.30pm
Location: Å80121
Eikonal phase and classical gravitational bound states
Speaker: Carlo Heissenberg
Papers:
- Eikonal phase and classical gravitational bound states 2212.13269
Date: 03 February 2023, 1.30pm
Location: Å80127
Power Corrections to Energy Flow Correlations from Large Spin Perturbation
Speaker: Giulia Fardelli
Papers:
- Power Corrections to Energy Flow Correlations from Large Spin Perturbation 2301.03616
Date: 27 January 2023, 1.30pm
Location: Å90101
Higher Gauging and Non-invertible Condensation Defects
Speaker: Elias Riedel Gårding
Papers:
- Higher Gauging and Non-invertible Condensation Defects 2204.02407
Date: 20 January 2023, 1.30pm
Location: Å80127
Talks - Fall 2022
On-shell constructibility of tree amplitudes in general field theories
Speaker: Zhewei Yin
Papers:
- On-shell constructibility of tree amplitudes in general field theories 1010.0257
Date: 09 December 2022, 1.30pm
Location: Å80121
Defect RG flows
Speaker: Jacopo Sisti
Abstract: After a quick introduction to defect CFTs, I will review the state of the art about monotonicity theorems for defect RG flows. Then, I will discuss the case of line defects following 2108.01117 and, if time permits, new results about phases of Wilson lines reported in 2211.11775.
Date: 02 December 2022, 1.30pm
Location: Å80121
Recursion Relations for 1-loop Goldstone Boson Amplitudes
Speaker: Christoph Bartsch (Prague)
Abstract: In recent years modern amplitude methods have been successfully applied to the study and classification of exceptional (scalar) effective field theories. In these theories tree-level amplitudes are completely fixed from consistent factorization and their soft behaviour (Adler zero). As a consequence, the tree-level S-Matrix can be recursively computed to all multiplicities from on-shell data alone. This is known as the soft bootstrap. In this talk I want to discuss the extension of these recursive techniques to the 1-loop planar integrand in the non-linear sigma model (NLSM). First, I will show that the integrand is no longer fixed by cuts and soft limits alone. Instead, the key to obtaining a unique integrand will be to study its single-cuts. I will propose two alternative criteria for the single-cuts that will both yield a unique definition of the integrand suitable for on-shell recursion. If time permits I will comment on preliminary work regarding the interpretation of the 1-loop single cuts and extending the procedure to two loops.
Date: 25 November 2022, 1.30pm
Location: Å80121
On continuous 2-category symmetries and Yang-Mills Theories.
Speaker: Giovanni Galati (SISSA)
Abstract: I will describe some interesting properties of continuous non-invertible symmetries enjoyed by some 4-dimensional free gauge theories. Thanks to a particular gauge fixing, I will explain how these theories can describe the kinematics of the UV limit of SU(N) Yang-Mills theories which therefore have an approximate non-invertible symmetry broken along the RG flow.
Date: 11 November 2022, 1.30pm
Location: Å80121
New recursions for tree-level correlators in (Anti) de Sitter space
Speaker: Lucile Cangemi
Papers:
- New recursions for tree-level correlators in (Anti) de Sitter space 2209.02709
Date: 28 October 2022, 1.30pm
Location: Å80121
Crossing Symmetric Dispersion Relations
Speaker: Ahmadullah Zahed (Indian Institute of Science, Bangalore)
Abstract: For 2-2 scattering in quantum field theories, the usual fixed t dispersion relation exhibits only two-channel symmetry. This paper considers a crossing symmetric dispersion relation, reviving certain old ideas in the 1970s. Rather than the fixed t dispersion relation, this needs a dispersion relation in a different variable z, which is related to the Mandelstam invariants s,t,u via a parametric cubic relation making the crossing symmetry in the complex z plane a geometric rotation. The resulting dispersion is manifestly three-channel crossing symmetric. We give simple derivations of certain known positivity conditions for effective field theories, including the null constraints, which lead to two sided bounds and derive a general set of new non-perturbative inequalities. We show how these inequalities enable us to locate the first massive string state from a low energy expansion of the four dilaton amplitude in type II string theory. We also show how a generalized (numerical) Froissart bound, valid for all energies, is obtained from this approach.
Date: 21 October 2022, 1.30pm
Location: Å80121
Towards the non-perturbative cosmological bootstrap
Speaker: Sourav Sarkar
Papers:
- Towards the non-perturbative cosmological bootstrap 2107.13871
Date: 14 October 2022, 1.30pm
Location: Å80121
Higher Form Symmetries: a review with application to 5d SCFT (from M-theory)
Speaker: Shani Nadir Meynet
Papers:
- Higher Form Symmetries and M-theory 2005.12831
- Generalized Global Symmetries 1412.5148
Date: 07 October 2022, 1.30pm
Location: Å80121
Speaker: Luca Cassia
Papers:
- When Does A Three-Dimensional Chern-Simons-Witten Theory Have A Time Reversal Symmetry? 2209.04519
Date: 30 September 2022, 1.30pm
Location: Å80121
Symmetry Protected Topological phases and Generalized Cohomology
Speaker: Matthew Magill
Papers:
- Symmetry Protected Topological phases and Generalized Cohomology 1712.07950
Date: 23 September 2022, 1.30pm
Location: Å80121
Heterotic Little String Theory, 2-groups and (Multi-)-T-duality
Speaker: Paul-Konstantin Oehlmann
Abstract: 6D Little String Theories (LSTs) share intriguing features of both SCFTs and SUGRA theories: They do have global symmetries but can also be related via T-duality. We are exploring novel 6D heterotic little strings related by T-duality using the geometry of F-theory and proofing the match of their Coulomb branch and global 2-group symmetries. We close by giving a general criterion on how to count T-dualities by enumerating elliptic fibrations of compact K3 surfaces that can have dozens of T-dual LSTs.
This talk is based on upcoming work with del Zotto & Liu from the 4th floor.
Date: 9 September 2022, 1.30pm
Location: Å80121