Amplifying Gravity at All Scales
from
Monday, June 26, 2023 (9:00 AM)
to
Friday, July 21, 2023 (6:00 PM)
Monday, June 26, 2023
9:00 AM
Registration
Registration
9:00 AM  10:00 AM
Room: Nordita, 6th floor
10:00 AM
Welcome  1st week
Welcome  1st week
10:00 AM  10:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
10:30 AM
Classical Double Copy: Solutions, Scattering, and Horizons

Cynthia Keeler
(
Arizona State University
)
Classical Double Copy: Solutions, Scattering, and Horizons
Cynthia Keeler
(
Arizona State University
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
We will review the classical double copy, beginning with the map between exact solutions. We will cover both the KerrSchild and Weyl formulations. Following a survey of known exact solutions, we will review why a positionspace classical solution double copy is even feasible. We will briefly discuss some perturbative approaches, and then close by relating several gravitational objects (including horizons) to their gauge theory analogues.
6:30 PM
Reception
Reception
6:30 PM  9:00 PM
Tuesday, June 27, 2023
10:30 AM
EFT Smatrix boostrap

Yutin Huang
(
NTU Taiwan
)
EFT Smatrix boostrap
Yutin Huang
(
NTU Taiwan
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
I will review the recent revival of Smatrix bootstrap in the context of massless EFTs. We will begin with the EFT of massless scalars, spinning and colored states and identify the data which we can hope to constrain. We will lay out the constraints of unitarity and locality in the UV and how it can be utilized to bound the low energy couplings through dispersion relations. We will focus in particular on gravitation systems, where the presence of massless poles requires a modern update to the bootstrap methods are required.
11:45 AM
ColorDual Constraints on Gravitational EFT

Nic Pavao
ColorDual Constraints on Gravitational EFT
Nic Pavao
11:45 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
I will discuss the recent developments regarding how colorkinematics duality places surprisingly rigid constraints on gravitational EFTs constructed from the double copy. We will begin with a review of colorkinematics and highlight the graphical simplicity that underlies the doublecopy construction. This background will pave the way for our main finding: the realization that colordual structure with factorization is sufficient to induce an infinite tower of constraints on higher derivative fourpoint operators. Remarkably, these colordual towers can be resummed, unveiling concealed particle residues, which are consistent with known UV completions of gravity.
Wednesday, June 28, 2023
10:30 AM
An introduction to flat space holography

Romain Ruzziconi
(
Vienna University of Technology
)
An introduction to flat space holography
Romain Ruzziconi
(
Vienna University of Technology
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
I will review some aspects of gravity in asymptotically flat spacetime and mention important challenges to obtain a holographic description in this framework. I will then present two important approaches towards flat space holography, namely Carrollian and celestial holography, and briefly explain how they are related to each other. Similarities and difference between flat and antide Sitter spacetimes will be emphasized throughout the talk.
11:45 AM
Celestial Soft Algebras

Walker Melton
Celestial Soft Algebras
Walker Melton
11:45 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
Gauge and gravity amplitudes have nearuniversal behavior in the limit where gravitons or gluons have low energies. In celestial CFT, these universal soft algebras imply the existence of higherspin current algebras. After discussing the origins of these celestial soft algebras from collinear limits of successive soft insertions, I will describe how gauge soft algebra of YangMills is extended when coupled to neutral complex scalars. Central extensions of the soft algebra for YangMills are generated by expanding around sourced scalar backgrounds.
Thursday, June 29, 2023
10:30 AM
Scattering amplitudes methods for gravitational waves

Andres Luna
(
NBI Copenhagen
)
Scattering amplitudes methods for gravitational waves
Andres Luna
(
NBI Copenhagen
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
I will review recent developments in techniques for the computation of scattering amplitudes in quantum field theory, and their application to the modelling of blackhole binaries and their waveforms. I will show the computation of a two body Hamiltonian, and a scattering angle in the second postMinkowskian approximation. Through this relatively simple example we will illustrate the use of spinor helicity, amplitudes bootstrap, double copy and unitarity, as well as diverse techniques to translate (the classical limit of) amplitudes into observables.
11:45 AM
On Massive Higher Spins and their Interactions

Lukas Lindwasser
On Massive Higher Spins and their Interactions
Lukas Lindwasser
11:45 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
There are several problems with modelling massive particles with spin higher than 1 coupled to electromagnetism or gravity. In this talk I will briefly outline these problems, and then show how gauge symmetry can solve some of them. I will also demonstrate that not every choice of gauge symmetry used in the formulation of massive higher spins is sufficient for this purpose.
6:30 PM
Dinner downtown
Dinner downtown
6:30 PM  9:00 PM
Friday, June 30, 2023
10:30 AM
Observables in expanding universes

Paolo Benincasa
(
MPI Munich
)
Observables in expanding universes
Paolo Benincasa
(
MPI Munich
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
The physics occurring in an expanding universe is encoded in correlation functions at his boundary. Part of its structure is inherited from the probability distributions of the field configuration at such boundary, or equivalently in the socalled wavefunction of the universe. I'll review the analytic structure of both the wavefunction and a certain class of correlation functions, their physical content their relation and how to compute the latter from the former. I'll finally discuss a geometrical picture which allows to talk about both quantities at once and to extract physical information that are obscure in the standard field theory language.
Saturday, July 1, 2023
Sunday, July 2, 2023
Monday, July 3, 2023
9:00 AM
Registration
Registration
9:00 AM  10:00 AM
Room: Nordita, 6th floor
10:00 AM
Welcome  2nd week
Welcome  2nd week
10:00 AM  10:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
10:30 AM
Double Copy in (A)dS

Arthur Lipstein
(
Durham
)
Double Copy in (A)dS
Arthur Lipstein
(
Durham
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
The double copy is a powerful theoretical tool which allows one to reduce complicated gravitational calculations to simpler ones in gauge theory. In this talk, I will describe recent progress in extending these techniques to (A)dS background. First I will explain how to formulate selfdual gravity in AdS4 in terms of a simple scalar theory which makes the double copy manifest and reveals some surprising new connections to celestial holography. I will then describe recent work which extends these ideas beyond the selfdual sector. In particular, I will present a compact new formula for the treelevel wavefunction coefficient of four gravitons in dS4, which was obtained by combining recently developed cosmological bootstrap methods with double copy intuition.
6:30 PM
Reception
Reception
6:30 PM  9:00 PM
Tuesday, July 4, 2023
10:30 AM
W algebras and ALE spaces

David Skinner
(
Cambridge
)
W algebras and ALE spaces
David Skinner
(
Cambridge
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
I’ll explain how the celestial chiral algebra of an ALE space can be easily read off from its twistor space. The simplest example is flat space, where the CCA is the loop algebra of the Poisson algebra of holomorphic functions on $\mathbb{C}^2$. We’ll also discuss the case of EguchiHanson space in some detail, where the CCA is related to a certain scaling limit of the family of Walgebras defined by Pope et al., where the scaling limit is controlled by the radius of the EguchiHanson core. The loop algebra of a general Walgebra (away from the scaling limit) similarly arises as the celestial chiral algebra of noncommutative selfdual gravity on EguchiHanson space. I’ll comment on the relevance of these results for potential topdown models of celestial holography in ALE spaces.
Wednesday, July 5, 2023
10:30 AM
On structures of celestial OPE and algebras

Lecheng Ren
(
Brown University
)
On structures of celestial OPE and algebras
Lecheng Ren
(
Brown University
)
10:30 AM  11:00 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
In this talk I will discuss several recent studies about soft OPE and algebra in celestial CFT. We first compute the deformation of the $w_{1+\infty}$ algebra of soft graviton, gluon and scalar currents in the Celestial CFT due to nonminimal couplings. We find that the Jacobi identity of the algebra, as well as the associativity of the OPE between these soft current operators, are satisfied only when the spectrum and couplings of the theory obey certain constraints. We also study the effect of these constraints on the amplitudes in the 4d bulk theory. We also determine tree level, allorder celestial operator product expansions (OPEs) of gluons and gravitons in the maximally helicity violating (MHV) sector from inverse soft recursion.
11:15 AM
Discussion on Celestial OPEs

Marcus Spradlin
(
Brown University
)
Discussion on Celestial OPEs
Marcus Spradlin
(
Brown University
)
11:15 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
I will lead a discussion on celestial OPE (non)associativity, effective field theories and their celestial duals, and related topics. The discussion is intended to be interactive, engaging, and provocative, so audience participation is expected.
Thursday, July 6, 2023
10:00 AM
Asymptotic symmetries and scattering amplitudes in flat space

Shamik Banerjee
(
Bhubaneswar, Inst. Phys.
)
Asymptotic symmetries and scattering amplitudes in flat space
Shamik Banerjee
(
Bhubaneswar, Inst. Phys.
)
10:00 AM  11:00 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
In this talk I will describe some works related to bootstrapping graviton ( and gluon) scattering amplitudes using asymptotic symmetries in four dimensional flat space time.
11:15 AM
Celestial holography on backgrounds

Bin Zhu
(
University of Edinburgh
)
Celestial holography on backgrounds
Bin Zhu
(
University of Edinburgh
)
11:15 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
The study of celestial holography on nontrivial backgrounds has recently gained interest. In this talk, I will give two specific examples. In the first example, I will show that the celestial MHV gluon amplitudes evaluated in the presence of a spherical dilaton shockwave are given by the correlation functions of primary field operators factorized into the holomorphic current operators times the “light” Liouville operators. They are evaluated in the semiclassical limit of Liouville CFT. A simple supersymmetric generalization in this context reveals celestial supersymmetry of the current sector. Then I will consider MHV amplitudes on selfdual radiative backgrounds as the second example. I will show that celestial soft gluon algebra and $w_{1+\infty}$ algebra are undeformed on these backgrounds.
6:00 PM
Dinner downtown
Dinner downtown
6:00 PM  8:30 PM
Friday, July 7, 2023
10:30 AM
The Kallen–Lehmann representation in de Sitter spacetime

Kamran Salehi Vaziri
(
Amsterdam University
)
The Kallen–Lehmann representation in de Sitter spacetime
Kamran Salehi Vaziri
(
Amsterdam University
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
We study twopoint functions of symmetric traceless local operators in the bulk of de Sitter spacetime. We derive the KallenLehmann spectral decomposition for any spin and show that unitarity implies its spectral densities are nonnegative. In addition, we recover the KallenLehmann decomposition in Minkowski space by taking the flat space limit. Using harmonic analysis and the Wick rotation to Euclidean Anti de Sitter, we derive an inversion formula to compute the spectral densities. Using the inversion formula, we relate the analytic structure of the spectral densities to the latetime boundary operator content. We apply our technical tools to study twopoint functions of composite operators in free and weakly coupled theories. In the weakly coupled case, we show how the KallenLehmann decomposition is useful to find the anomalous dimensions of the late time boundary operators. We also derive the KallenLehmann representation of twopoint functions of spinning primary operators of a Conformal Field Theory on de Sitter.
Saturday, July 8, 2023
Sunday, July 9, 2023
Monday, July 10, 2023
9:00 AM
Registration
Registration
9:00 AM  10:00 AM
Room: Nordita, 6th floor
10:00 AM
Welcome  3rd week
Welcome  3rd week
10:00 AM  10:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
10:30 AM
Stringbased vs. stringinspired in quantum gravity

Christian Schubert
Stringbased vs. stringinspired in quantum gravity
Christian Schubert
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
It has been understood since the eighties that string theory amplitudes are in various aspects better organised than amplitudes in ordinary quantum field theory. One can try to exploit this fact either by representing field theory amplitudes as the infinite stringtension limit of string amplitudes (``stringbased formalism’’), or by representing them by worldline path integrals and evaluating those in a way analogous to string theory (``stringinspired formalism’’). Here I review and compare both approaches with an emphasis on gravity amplitudes and aspects of YangMills theory that bear a relevance for gravity such as colorkinematics duality and multiparticle states. A central role is played by the cycleandtail decomposed worldline integrands of the oneloop Ngluon amplitudes that have recently tuned out to provide a natural route to the construction of BerendsGiele currents in BCJ gauge for YangMills theory as well as gravity.
11:45 AM
11D superfields and vertex operators in the pure spinor formalism

Maor BenShahar
(
Uppsala University
)
11D superfields and vertex operators in the pure spinor formalism
Maor BenShahar
(
Uppsala University
)
11:45 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
To compute observables in the pure spinor description of 11D supergravity we need vertex operators, a good handle on the pure spinor measure, and a prescription for constructing invariants in pure spinor superspace. In this talk I will describe recent work [2305.19898 ] on the construction of superfields and vertex operators. This entails obtaining recursion relations for the superfields by appropriately gauge fixing the linearized superspace equations of motion. At the end of the talk I will also discuss upcoming work on the pure spinor measure.
6:00 PM
Reception
Reception
6:00 PM  8:30 PM
Tuesday, July 11, 2023
10:30 AM
Modular constraints on N=4 SYM / type IIB holography

Michael Green
Modular constraints on N=4 SYM / type IIB holography
Michael Green
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
11:45 AM
The Road to Seven Loops in N=8 SUGRA

Alex Edison
(
Northwestern University
)
The Road to Seven Loops in N=8 SUGRA
Alex Edison
(
Northwestern University
)
11:45 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
I'll provide a brief history of the multiloop N=8 integrand program: how three and four loops were relatively straightforward, what goes wrong at five loops, and why that means going further requires new insights. I'll then discuss some recent, inprogress, and nearfuture calculations at lower loops that are searching for these insights.
2:15 PM
KawaiLewellenTye relations / constructions

Johannes Broedel and Stephan Stieberger .
KawaiLewellenTye relations / constructions
Johannes Broedel and Stephan Stieberger .
2:15 PM  3:45 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
Wednesday, July 12, 2023
10:30 AM
Higherorder calculations: Recent developments from Feynman integrals

Stefan Weinzierl
Higherorder calculations: Recent developments from Feynman integrals
Stefan Weinzierl
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
In this talk I will review recent developments in the field of analytical Feynman integral calculations. In particular, I will discuss Feynman integrals related to nontrivial geometries like an elliptic curve, or more general a CalabiYau manifold, and methods how to compute these Feynman integrals.
Thursday, July 13, 2023
10:30 AM
Revisiting Hyperelliptic Feynman Integrals

Andrew McLeod
Revisiting Hyperelliptic Feynman Integrals
Andrew McLeod
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
While Feynman diagrams that give rise to elliptic curves and higherdimensional CalabiYau manifolds have received a great deal of attention in recent years, much less attention has been paid to examples that involve hyperelliptic curves. In this talk, I will revisit some of the simplest Feynman diagrams that are known to be hyperelliptic, and show that the curves these diagrams give rise to satisfy a hidden involution symmetry that allow them to be mapped to curves of lower genus. This represents a significant simplification in the types of functions that these diagrams are expected to evaluate to. I will then go on to motivate the importance of studying hyperelliptic Feynman diagrams by constructing an allloop class of vacuum diagrams that give rise to hyperelliptic curves of every genus.
11:45 AM
New probes of the string spectrum

Chrysoula Markou
(
University of Mons
)
New probes of the string spectrum
Chrysoula Markou
(
University of Mons
)
11:45 AM  12:15 PM
Room: Albano 3: 4204  SU Conference Room (56 seats)
As is well known, the string spectrum comprises infinitely many states that can collectively be visualised along Regge trajectories of increasing mass and spin. Its massless level, low spins as well as certain higher spins including the leading Regge trajectory have been the focus of past studies. In this talk, we will discuss new probes beyond the leading Regge, starting with recent work on the interactions of subleading massive spin2 superstring states and proceeding to ongoing work on whole families of subleading Regge trajectories as well as their interactions using string scattering amplitudes.
6:00 PM
Dinner downtown
Dinner downtown
6:00 PM  8:00 PM
Friday, July 14, 2023
10:30 AM
SevenPoint Singularities and the OneLoop ngon Integral

Anastasia Volovich
(
Brown University
)
SevenPoint Singularities and the OneLoop ngon Integral
Anastasia Volovich
(
Brown University
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
This talk will cover two separate topics on the mathematical structure of Feynman integrals and scattering amplitudes. In the first part, I will discuss an attempt to determine what can be said, on general grounds, about the singularities of sevenpoint amplitudes in massless planar theories. One motivation is that this provides essential input into the bootstrap program that has allowed the computation of these amplitudes to high loop order in N=4 YangMills. In the second part, I will explain how a recent mathematical result on volumes of orthoschemes can be used to provide an explicit analytic result for the oneloop scalar ngon Feynman integral in n dimensions, for even n, with massless or massive internal and external edges.
Saturday, July 15, 2023
Sunday, July 16, 2023
Monday, July 17, 2023
9:00 AM
Registration
Registration
9:00 AM  10:10 AM
Room: Nordita, 6th floor
10:10 AM
Welcome  4th week
Welcome  4th week
10:10 AM  10:30 AM
Room: Albano 2: C2207  Auditorium 4 (80 seats)
10:30 AM
Gravitational Waveforms from Amplitudes

Donal O'Connell
(
University of Edinburgh
)
Gravitational Waveforms from Amplitudes
Donal O'Connell
(
University of Edinburgh
)
10:30 AM  11:30 AM
Room: Albano 2: C2207  Auditorium 4 (80 seats)
Scattering amplitudes are useful for computing many quantities in gravitational wave physics. In this talk I I will discuss the determination of gravitational waveforms in scattering encounters at LO and NLO in the postMinkowskian expansion. I will explain some of the methods which can be used to simplify the calculation, and comment on links to more classical methods.
6:30 PM
Reception
Reception
6:30 PM  9:00 PM
Tuesday, July 18, 2023
10:30 AM
Highprecision gravitational wave physics from a worldline quantum field theory

Jan Plefka
(
Humboldt University
)
Highprecision gravitational wave physics from a worldline quantum field theory
Jan Plefka
(
Humboldt University
)
10:30 AM  11:30 AM
Room: Albano 2: C2207  Auditorium 4 (80 seats)
I will review the worldline approach to reach high order PM results for the general relativistic twobody scattering problem thereby importing powerful multiloop techniques from quantum field theory. We will discuss the simple structure of the classical limit amounting to the need to evaluate onepoint functions in worldline quantum field theory at the treelevel, the inclusion of spin degrees of freedom via a worldline supersymmetry, the need to use the SchwingerKeldysh formalism leading to the use of retarded propagators, as well as a discussion of the integration pipeline used in our approach. I will report on the recent completion of the 4PM spinorbit computation for the impulse, scattering angle and spinkick — both in the conservative and disspative cases. The later confirming the 4PM radiation reaction nonspinning results of Porto, Källen, Dlapa, Neff and Liu.
Wednesday, July 19, 2023
10:30 AM
Selfforce in hyperbolic scattering

Leor Barack
(
University of Southampton
)
Selfforce in hyperbolic scattering
Leor Barack
(
University of Southampton
)
10:30 AM  11:30 AM
Room: Albano 3: 4204  SU Conference Room (56 seats)
The first part will review the foundations of gravitational selfforce theory in classical GR: a perturbative approach to the 2body problem based on a systematic expansion of the field equations in the mass ratio, assumed small. The second part will describe recent work to apply selfforce methods to the blackhole scattering problem, including a comparison with postMinkowskian results from Amplitude calculations in a scalarcharge toy model.
Thursday, July 20, 2023
10:30 AM
Massive gravity in the Swampland

Giulia Isabella
(
Geneva University
)
Massive gravity in the Swampland
Giulia Isabella
(
Geneva University
)
10:30 AM  11:00 AM
Room: Albano 2: C2207  Auditorium 4 (80 seats)
I will discuss new positivity bounds at finite momentum transfer, showing that massive gravity parametrically violates these bounds unless the cutoff is within one order of magnitude of the graviton mass. These results effectively rule out massive gravity as a long distance theory consistent with a causal and unitary UV completion.
11:15 AM
Higher spins, the Teukolsky equation and SuperExtremal Kerr Binary Systems

Fabian Bautista
(
IPhT Saclay
)
Higher spins, the Teukolsky equation and SuperExtremal Kerr Binary Systems
Fabian Bautista
(
IPhT Saclay
)
11:15 AM  11:45 AM
Room: Albano 2: C2207  Auditorium 4 (80 seats)
In this talk, we will review the extraction of a higher spin gravitational Compton amplitude from lowenergy solutions of the Teukolsky equation in the superextremal (SE) Kerr region (a/Gm ≫ 1), for the scattering of a gravitational wave off the Kerr black hole (BH). We will then use this amplitude to study the nonradiative dynamics for binary systems formed by SE Kerr BHs with their spin oriented in generic directions, up to second order in the postMinkowskian expansion.
7:00 PM
Dinner downtown
Dinner downtown
7:00 PM  9:00 PM
Friday, July 21, 2023
10:30 AM
Kerr black holes from amplitudes and effective field theory

Andreas Helset
(
Caltech
)
Kerr black holes from amplitudes and effective field theory
Andreas Helset
(
Caltech
)
10:30 AM  11:30 AM
Room: Albano 2: C2207  Auditorium 4 (80 seats)
Spin effects for Kerr black holes can be included systematically in fieldtheoretic calculations of the twobody problem. I will discuss one approach to incorporate spin which uses the synergy between onshell scattering amplitudes and heavy particle effective theory (HPET). This framework is tailored to extract the classical parts of the computation and it exposes structure in the spinmultipole expansion. Some results from this approach include recent calculations to all orders in the spins of the black holes.