Talks - Spring 2023
Eikonal phase and classical gravitational bound states
Speaker: Carlo Heissenberg
- Eikonal phase and classical gravitational bound states 2212.13269
Date: 03 February 2023, 1.30pm
Power Corrections to Energy Flow Correlations from Large Spin Perturbation
Speaker: Giulia Fardelli
- Power Corrections to Energy Flow Correlations from Large Spin Perturbation 2301.03616
Date: 27 January 2023, 1.30pm
Higher Gauging and Non-invertible Condensation Defects
Speaker: Elias Riedel Gårding
- Higher Gauging and Non-invertible Condensation Defects 2204.02407
Date: 20 January 2023, 1.30pm
Talks - Fall 2022
On-shell constructibility of tree amplitudes in general field theories
Speaker: Zhewei Yin
- On-shell constructibility of tree amplitudes in general field theories 1010.0257
Date: 09 December 2022, 1.30pm
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
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
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
New recursions for tree-level correlators in (Anti) de Sitter space
Speaker: Lucile Cangemi
- New recursions for tree-level correlators in (Anti) de Sitter space 2209.02709
Date: 28 October 2022, 1.30pm
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
Towards the non-perturbative cosmological bootstrap
Speaker: Sourav Sarkar
- Towards the non-perturbative cosmological bootstrap 2107.13871
Date: 14 October 2022, 1.30pm
Higher Form Symmetries: a review with application to 5d SCFT (from M-theory)
Speaker: Shani Nadir Meynet
Date: 07 October 2022, 1.30pm
When Does A Three-Dimensional Chern-Simons-Witten Theory Have A Time Reversal Symmetry?
Speaker: Luca Cassia
- When Does A Three-Dimensional Chern-Simons-Witten Theory Have A Time Reversal Symmetry? 2209.04519
Date: 30 September 2022, 1.30pm
Symmetry Protected Topological phases and Generalized Cohomology
Speaker: Matthew Magill
- Symmetry Protected Topological phases and Generalized Cohomology 1712.07950
Date: 23 September 2022, 1.30pm
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