# 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:** Carlos Rodriguez (carlos.rodriguez@physics.uu.se)

## Talks - Fall 2023

**Unraveling the Holomorphic Twist: Central Charges**

**Speaker: **Charles Thull

**Papers:**

- Unraveling the Holomorphic Twist: Central Charges 2311.04304

**Date:** 17 November 2023, 1.30pm

**Location:** Å90101

**Machine learning phases of matter**

**Speaker: **Carlos Rodriguez

**Papers:**

- Machine learning phases of matter 1605.01735

**Date:** 10 November 2023, 1.30pm

**Location:** Å92110

**Generalized Landau Paradigm: A Consistency Check on the Abelian Higgs Model**

**Speaker: **Daniele Migliorati

**Abstract:** I will review various aspects of generalized symmetries and their application in characterizing the phase of a gauge theory. After introducing the general paradigm, I will apply this framework to the Abelian Higgs Model, exploring its infrared theory and deriving the constraints that generalized symmetries impose on the low-energy theory.

**Date:** 03 November 2023, 1.30pm

**Location:** Å80115

**Topological field theory and anomalies**

**Speaker: **Shani Nadir Meynet

**Abstract:** In the last years the paradigm for understanding the symmetries of quantum field theories has shifted towards the concept of the so called SymmetryTFT, a topological field theory encoding the data of all possible realizations of global and higher group structures. In this brief talk we will review some aspects of topological field theory and how standard techniques allow to reinterpret anomalies in term of topological invariants. As an example, we will discuss the case of 5d SCFT constructed via geometric engineering, commenting in particular the relation between wrapped branes, topological operators and generalized membranes link.

**Papers:**

- Symmetry TFTs and Anomalies of Non-Invertible Symmetries 2301.07112
- Symmetry TFTs for Non-Invertible Defects 2209.11062
- Braiding Statistics and Link Invariants of Bosonic/Fermionic Topological Quantum Matter in 2+1 and 3+1 dimensions 1612.09298

**Date:** 20 October 2023, 1.30pm

**Location:** Å80115

**Speaker: **Sam Wikeley

**Date:** 13 October 2023, 1.45pm

**Location:** Å101190

**On scale separation — or small extra dimensions — in string theory**

**Speaker: **Vincent Van Hemelryck

**Abstract:** Following a brief self-introduction, I will delve into the topic of scale separation within the realm of string theory. This concept revolves around the observation that compactifications of ten-dimensional string theory do typically not lead to genuine lower-dimensional effective field theories. Specifically, the KK length scale or the size of the extra dimensions tends to be the same magnitude as the cosmological scale, resulting in an absence of separation between these scales. However, there are a few models that do achieve scale separation. In this presentation, I will present a new construction of a 4d scale-separated vacuum in type IIA that alleviates some of the issues from the previous models. Finally, I will elaborate on how one can interpolate between the different type IIA vacua by the use of a new open-string scalar field.

**Date:** 15 September 2023, 1.45pm

**Location:** Å4004

**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

**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