Celestial Holography Summer School 2024

Jul 22, 2024, 8:00 a.m. → Jul 26, 2024, 5:00 p.m. America/Toronto

PI/1-100 - Theatre (Perimeter Institute for Theoretical Physics)

Perimeter Institute is happy to host the inaugural summer school for the Simons Collaboration on Celestial Holography July 22-26 in Waterloo, ON. The program will feature lectures on background material relevant for graduate students and postdocs interested in this emerging subfield, paired with vision talks on exciting future research directions.

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Celestial Holography (1a-1b) Ana-Maria Raclariu.pdf

Monday, July 22

8:00 a.m. Registration

1 OPENING REMARKS

2 Lecture - Celestial Holography Ia

Speaker: Ana-Maria Raclariu (King's College London)

Celestial Holography (1a-1b) Ana-Maria Raclariu.pdf

3 Lecture - Canonical a

Speaker: Prahar Mitra (University of Amsterdam)

11:00 a.m. Break

4 Lecture - Celestial Holography Ib

Speaker: Ana-Maria Raclariu (King's College London)

Celestial Holography (1a-1b) Ana-Maria Raclariu.pdf

12:30 p.m. Lunch

5 Lecture - Amplitudes a

Speaker: Sebastian Mizera (Institute for Advanced Study)

3:30 p.m. Break

6 Vision Talk - Celestial symmetries from twistor theory

Celestial symmetry algebras arise from the OPEs of soft gravitons giving rise to the so-called `Lw_{1+\infty} algebra'. This talk will explain how this algebra can be can be understood as the local structure preserving local diffeomorphisms of twistor space. This can be naturally deformed to yield analogues with cosmological constant following https://arxiv.org/abs/2403.18011. We also give a brief introduction to twistor space actions to show how Noether arguments can be used to obtain improved associated charge and flux integrals as originally found by Friedel, Pranzetti and Raclariu; this is joint work with Adam Kmec, Romain Ruzziconi and Akshay Yelleshpur-Srikant https://arxiv.org/abs/2407.04028. If there is time there will be some further open-ended discussion of open questions in celestial holography via twistor theory.

Speaker: Lionel Mason (University of Oxford)

4:45 p.m. Free Time

6:45 p.m. TA Session - Celestial Holography (Sruthi Narayanan / Adam Ball)

Tuesday, July 23

7 Lecture - Celestial Holography IIa

Speaker: Andrea Puhm (Ecole Polytechnique - CPHT)

8 Lecture - Canonical b

Speaker: Prahar Mitra (University of Amsterdam)

11:00 a.m. Break

9 Lecture - Celestial Holography IIb

Speaker: Andrea Puhm (Ecole Polytechnique - CPHT)

12:30 p.m. Group Photo

12:40 p.m. Lunch

10 Lecture - Amplitudes b

Speaker: Sebastian Mizera (Institute for Advanced Study)

3:30 p.m. Break

11 Vision Talk - Taking Λ out of It?

Speaker: Rob Myers (Perimeter Institute)

4:45 p.m. Poster Session

6:45 p.m. TA Session - Canonical/Carollian (Luca Ciambelli)

Wednesday, July 24

12 Lecture - Carrollian Physics a

Speaker: Romain Ruzziconi (University of Oxford)

13 Lecture - IR S-matrix a

Speaker: Hofie Hannesdottir (Institute for Advanced Study)

11:00 a.m. Break

11:30 a.m. TA Session - Amplitudes

12:30 p.m. Lunch

2:30 p.m. // Free Time

Lightning Talks

14 Asymptotic symmetries for logarithmic soft theorems

In the last few years, a remarkable link has been established between the soft theorems and asymptotic symmetries of quantum field theories: soft theorems are Ward identities of the asymptotic symmetry generators. In particular, the tree-level subleading soft theorems are the Ward identities of the subleading asymptotic symmetries of the theory, for instance divergent gauge transformation in QED and superrotation in gravity. However, it is known that the subleading soft theorems receive quantum corrections with logarithmic dependence on the soft photon/graviton energy. It is therefore natural to ask how the quantum effects affect the classical (tree-level) symmetry interpretation. In this talk, we explore this question in the context of scalar QED and perturbative gravity. We show that the logarithmic soft theorems are the Ward identities of subleading asymptotic symmetries that arise from relaxed boundary conditions which take long-range interactions into account.

Speaker: Sangmin Choi (University of Amsterdam)

15 Quantum Corrections to the Thermodynamics of Cold Black Holes

I will review an old puzzle related to the breakdown of the semiclassical description of the thermodynamics of very cold (ultraspinning) black holes. Then, I will discuss recent work where we resolved this puzzle by properly accounting for quantum corrections arising from graviton loops, which dominate the low-temperature thermodynamics.

Speaker: Ahmed Sheta

16 Celestial Chiral Algebras of self-dual Black Holes

This talk is based on work in progress with Giuseppe Bogna. We consider the twistor description of classical self-dual Einstein gravity in the presence of a cosmological constant and a defect operator wrapping a certain $\mathbb{CP}^1$. The backreaction of this defect deforms the flat twistor space to that of quaternionic Taub-NUT space, a certain self-dual limit of a family of Kerr Taub-NUT AdS black holes. We discuss a 2-parameter family of Lie-algebras depending on the mass of the black hole and the cosmological constant. In various limits it reduces to algebras which were previously studied in the context of celestial holography and are closely related to $w_{1+\infty}$.

Speaker: Simon Heuveline (University of Cambridge)

17 A Celestial Dual for MHV Amplitudes

We show that a 2D CFT consisting of a central charge c Liouville theory, a chiral level one, rank N Kac-Moody algebra and a weight −3/2 free fermion holographically generates 4D MHV leaf amplitudes associated to a single hyperbolic slice of flat space. Celestial amplitudes arise in a large-N and semiclassical large-c limit, according to the holographic dictionary, as a translationally-invariant combination of leaf amplitudes. A step in the demonstration is showing that the semiclassical limit of Liouville correlators are given by contact AdS3 Witten diagrams.

Speaker: Mr Walker Melton (Harvard University)

18 Collinear singularities from a double cover of twistor space

Based on an idea of Kevin Costello, I will show how to construct a double cover of the twistor space of $\mathbb{R}^4$, $X = \pi^*(\mathcal{O}(1)\oplus\mathcal{O}(1))\to\Sigma$ where $\Sigma$ is an (hyper)elliptic curve. I then discuss how holomorphic theories such as BF and Chern-Simons theory on $X$ descend to theories on ordinary twistor space. Once on twistor space, compactifying along the $\mathbb{CP}^1$ direction of twistor space produces a corresponding 4d theory where we can study the algebra of collinear singularities. I will present my calculations which show that this algebra lives on the elliptic curve defining the double cover of twistor space.

Speaker: Seraphim Hsieh Jarov (Perimeter Institute)

19 The Bulk Model of Dissipative Dynamics On Lie Group

Speaker: Mr Afshin Besharat (McMaster University and Perimeter Institute)

20 Higher-Spin Charges in Gravity

I will describe shortly what the higher-spin charges are and why they are relevant from a holographic point of view. Besides, I will emphasize the recent result according to which they are realized as Noether charges in a non-linear regime.

Speaker: Nicolas Cresto (Perimeter Institute)

4:45 p.m. // Free Time

6:00 p.m. Banquet

Thursday, July 25

21 Lecture - Carrollian Physics b

Speaker: Romain Ruzziconi (University of Oxford)

22 Lecture - IR S-matrix b

Speaker: Hofie Hannesdottir (Institute for Advanced Study)

11:00 a.m. Break

11:30 a.m. TA Session - IR S-matrix

12:30 p.m. Lunch

23 Lecture - Twistors a

Speaker: David Skinner (University of Cambridge)

3:30 p.m. Break

24 Vision Talk - Celestial holography: past, present and future

Speaker: Andy Strominger (Harvard University)

4:45 p.m. // Free Time

6:45 p.m. TA Session - Twistors / Twisted Holography (Roland Bittleston / Kasia Budzik)

Friday, July 26

25 Lecture - Twistors b

Speaker: David Skinner (University of Cambridge)

26 Lecture - Twisted Holography a

Speaker: Davide Gaiotto (Perimeter Institute)

11:00 a.m. Break

27 Lecture - Twisted Holography b

Speaker: Davide Gaiotto (Perimeter Institute)

12:30 p.m. Lunch

28 Panel Discussion

Speakers: Andrea Puhm (Ecole Polytechnique - CPHT), David Skinner (University of Cambridge), Kevin Costello, Laurent Freidel (Perimeter Institute), Sabrina Pasterski

29 CLOSING REMARKS