Journalklubb

Målgruppen för journalklubben är doktorander och postdocs som forskar om olika ämnen inom teoretisk fysik. Idén är att vi möts för att lära oss och diskutera klassiska och intressanta ämnen inom teoretisk fysik.
Organisatör: Giulia Fardelli (giulia.fardelli@physics.uu.se)

Talks - Spring 2023

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:

Date: 07 October 2022, 1.30pm
Location: Å80121


When Does A Three-Dimensional Chern-Simons-Witten Theory Have A Time Reversal Symmetry?

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

Senast uppdaterad: 2023-01-30