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 2022

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


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

Talks - Spring 2022

Islands outside the horizon

Speaker: Filip Landgren

Abstract: By considering the entanglement wedge of the Hawking radiation of an evaporation black hole so called entanglement islands will appear. In this talk I will present how these islands can be used to derive the Page curve, thus solving one aspect of the information paradox. I will show where these islands come from and how they can be derived using a standard replica trick. This work was awarded the Breakthrough New Horizons prize in 2021 and gained huge traction. In this 2d toy model an AdS black hole was coupled to a flat heat bath in which the radiation could escape into. I will also present some pressing issues with this model as well as how to move beyond it.
Papers:

  • Islands outside the horizon 1910.11077
  • Replica Wormholes and the Entropy of Hawking Radiation 1911.12333

Date: 17 June 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Constraints from unitarity on q-strings

Speaker: Maor Ben-Shahar
Papers:

  • On the unitarity and low energy expansion of the Coon amplitude 2201.12331
  • Extremal Effective Field Theories 2011.02957

Date: 10 June 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Cobordism Classes and the Swampland

Speaker: Matthew Magill
Papers:

Date: 03 June 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Riding bubbles to take off from the swamp

Speaker: Daniel Panizo
Papers:

  • de Sitter cosmology on an expanding bubble 1907.04268
  • Curing with hemlock: escaping the swampland using instabilities from string theory 2103.17121
  • Daniel's notes for the talk: pdf, pdf

Date: 13 May 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Macaulay Matrix for Feynman Integrals: Linear Relations and Intersection Numbers

Speaker: Carlos Rodriguez
Papers:

  • Macaulay Matrix for Feynman Integrals: Linear Relations and Intersection Numbers 2204.12983

Date: 06 May 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Gaudin Models and Multipoint Conformal Blocks

Speaker: Simon Ekhammar
Papers:

  • Gaudin Models and Multipoint Conformal Blocks: General Theory 2105.00021

Date: 22 April 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Broken R-symmetry and defect conformal manifolds

Speaker: Charles Thull
Papers:

  • Broken R-symmetry and defect conformal manifolds 2203.17157

Date: 08 April 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Non-invertible Duality Defects

Speaker: Vladimir Bashmakov
Papers:

  • Kramers-Wannier-like duality defects in (3+1)d gauge theories 2111.01141
  • Non-invertible Duality Defects in 3+1 Dimensions 2111.01139

Date: 25 March 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Geometry-Kinematics Duality

Speaker: Lucia Garozzo
Papers:

Date: 18 March 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Localised magnetic field in the O(N) model

Speaker: Parijat Dey
Papers:

  • Localised magnetic field in the O(N) model 2112.10634

Date: 11 March 2022, 1.30 pm
Location: Å80127 or Zoom https://uu-se.zoom.us/j/69181515232


Classical Double Copy of Worldline Quantum Field Theory

Speaker: Filippo Balli
Papers:

  • Classical Double Copy of Worldline Quantum Field Theory 2109.10345

Date: 04 March 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Test black holes, scattering amplitudes and perturbations of Kerr spacetime

Speaker: Justin Vines (AEI Potsdam)
Papers:

  • Test black holes, scattering amplitudes and perturbations of Kerr spacetime 1909.07361

Date: 25 February 2022, 1.30 pm
Location: Å80101 or Zoom https://uu-se.zoom.us/j/69181515232


On-shell Correlators and Color-Kinematics Duality in Curved Symmetric Spacetimes

Speaker: Alex Edison
Papers:

  • On-shell Correlators and Color-Kinematics Duality in Curved Symmetric Spacetimes 2201.05147

Date: 18 February 2022, 1.30 pm
Location: Å80101 or Zoom https://uu-se.zoom.us/j/69181515232


AdS Bulk Locality from Sharp CFT Bounds

Speaker: Giulia Fardelli
Papers:

  • AdS Bulk Locality from Sharp CFT Bounds 2106.10274

Date: 04 February 2022, 1.30 pm
Location: Å4004 or Zoom https://uu-se.zoom.us/j/69181515232


Where is String Theory?

Speaker: Alessandro Georgoudis
Papers:

Date: 04 February 2022, 1.30 pm
Location: Å80115 or Zoom https://uu-se.zoom.us/j/69181515232


A Note on Complex Spacetime Metrics

Speaker: Rodolfo Panerai
Papers:

Date: 28 January 2022, 1.30 pm
Location: Å80121 or Zoom https://uu-se.zoom.us/j/69181515232


Automorphic Spectra and the Conformal Bootstrap

Speaker: Andrea Manenti
Papers:

  • Automorphic Spectra and the Conformal Bootstrap 2111.12716

Date: 21 January 2022, 1.30 pm
Location: Å4005 or Zoom https://uu-se.zoom.us/j/69181515232

Last modified: 2022-11-22