fpuk and the City 2 December 2022 City University 
Local Organiser: B. Stefanski
Organising Committee: D.
Berman, J. Gauntlett, P. Kumar, N. Lambert, S. Ross,
S. SchaferNameki, M. Taylor and D. Tong
Schedule:

December 2^{nd} 


09:45 
Registration 
10:00 

10:20 

10:40 

11:00 
Break 
11:30 

11:50 

12:10 

12:30 

13:00 
Lunch and posters 
14:30 

14:50 

15:10 

15:30 
Break 
16:00 

16:20 

16:40 
Wine and cheese 
Registration for talks and posters has closed.
You are still welcome to attend but please let us know by email
Directions:
The talks will take place in room BG03 in the University Building, with
the poster session and lunch in C302 in Tait building.
The buildings are connected internally and can both be accessed through
the card less main entrance in Northampton
square.
The nearest tube stops are Farringdon and Angel. King’s Cross/St Pancras train
station is about 20 a minute walk.
Talks:
Connor Behan (Oxford):
Coupled Minimal
Models Revisited
It is widely believed that
two copies of the 3d Ising model, coupled via their
energy operators, will flow to the O(2) model in the
IR. In two dimensions, one also has the option of coupling higher minimal
models together. These offer a number of underexplored
possibilities for triggering RG flows that are arbitrarily weakly coupled. I
will give an overview of the zoo of fixed points one can obtain. Importantly,
some of the tools most helpful for analyzing them did
not exist ten years ago. I will focus on multiplet
recombination and how it provides strong evidence for the irrationality of
these CFTs.
Mariana Carrillo Gonzalez (Imperial):
Massive
gravitons from the double copy
The double copy is a
relation that allows us to write gravitational phenomena as the
"square" of the analog YangMills
phenomena. This simplifies involved gravitational calculations and gives an
insight into hidden symmetries of gravity. Given the possibility of having a
massive graviton that can explain the acceleration of the Universe, it is
interesting to understand whether this relationship extends to this case. In my
talk I will introduce the BCJ double copy and the colorkinematics
duality, and I will explain how to start generalizing this to massive
gravitons. I will focus on the 3dimensional case of topologically massive
gravity and will give examples of different realizations of the topologically
massive double copy. This presentation will be based on 2111.15405 and
2207.04431.
Andrea Ferrari
(Durham): Noninvertible
symmetries and higher representation theory
There has recently been a lot
of excitement surrounding noninvertible global symmetries and their potential
applications. An important question is how to systematically construct theories
whose noninvertible symmetry categories we can control well. In this talk I
will suggest that higher representation theory can help us to answer this
question when the symmetries are nonintrinsically noninvertible. In particular, I will explain how the topological defects
obtained after gauging finite groups and 2groups in 3 dimensions form the
category of 2representations of the original 2group, and how this fact can be
applied to some gauge theories with disconnected gauge groups. The same
techniques can be extended to more general higher groups and subgroups in
higher dimensions.
Sagar Hosseini
(Durham): Generalised
Symmetries and anomalies from higher dimensions
Recently, there has been
much interest in the study of symmetries in physical systems as they
characterise topological aspects of quantum field theories. An important
realisation is that symmetries, their anomalies and BF
theory in a given QFT may be characterised in one higher dimension by a
symmetry topological field theory (SymTFT) via inflow
mechanics. Such descriptions can naturally emerge whenever we can construct
quantum field theories from string theory. In this talk, I will introduce SymTFTs and explain how to construct them from geometry.
Julius Julius (KCL): Bootstrability for 1d
defect CFT
I will describe the bootstrability program, which
combines integrability techniques in 4d N = 4 SYM and the conformal bootstrap
to study beyondthespectrum observables in a CFT.
I will start with a quick review of the quantum spectral curve (QSC), a
powerful integrability based method to compute the nonperturbative planar
spectrum of N = 4 SYM. I will show how it is modified to capture the spectrum
of operator insertions on a 1/2BPS MaldacenaWilson line in the theory, thus
solving the spectral problem of the associated defect CFT.
Then, I will show how the boostrability approach
allows us to access previously unreachable quantities such as correlation
functions at finite coupling ‚Äî we used this method
to compute with good precision a nonsupersymmetric structure constant for a
wide range of the ‘t Hooft coupling in the defect CFT.
Finally, I will present recent results, where we included further spectral
input, in order to derive novel integral constraints for our bootstrap
procedure, which allows us to improve the precision of our results by several
orders of magnitude.
Avner Karasik
(Cambridge): On
anomalies and gauging of U(1) noninvertible
symmetries in 4d QED.
I will present a way to
promote the anomalous axial U(1) in 4d QED to an exact
symmetry, with the price of losing its invertibility. I will then discuss some
applications of this noninvertible U(1) symmetry. In
particular, I will show how to gauge this symmetry and how to study its
'tHooft anomalies.Based on
2211.05802
Rifath Khan (Cambridge): Cauchy Slice Holography
In the Canonical theory of
Quantum Gravity (CQG), states are given by the superposition of geometries on a
Cauchy slice, called the WheelerDeWitt (WDW) states. On the other hand, the
Holographic principle states that quantum gravity in d+1 spacetime dimensions
is the same as a quantum field theory in d spacetime dimensions. In this talk,
I will briefly review both of these and will explain
how to reformulate CQG as a holographic theory by defining a new holographic
dictionary that maps any state of the boundary field theory to a bulk WDW
state. This dictionary is an isomorphism between the Hilbert space of CQG and
holographic CFT. This also reformulates the holographic principle in a way that
the dual field theory now lives on Cauchy slices of the bulk, hence applicable
to dS and flat spacetimes too. I will then explain
why this is a manifestly background independent theory of effective quantum
gravity. Time permitting, I will also discuss UV completion of quantum gravity,
and holographic cosmology. Based on work with Goncalo AraujoRegado and Aron C. Wall: arXiv:2204.00591.
Sujay Nair
(Oxford): Chiral
algebras for twisted class S
The SCFT/VOA correspondence
of BeemLemosLiendoPeelaersRastellivan Rees
leads to a particularly rich family of vertex algebras when applied to the
theories of class S. A remarkably uniform construction of these, so called,
'chiral algebras of class S' has been put forward by Arakawa in
arxiv:1811.01577. This construction takes a simple Lie algebra as an input and
applies equally well in the nonsimply laced case. However, the nonsimply
laced construction does not correspond, in any clear way, to known
fourdimensional theories.
Physically, the
incorporation of nonsimply laced symmetry algebras requires the inclusion of
outer automorphism twists. I will detail an extension of Arakawa's construction
to this twisted setting. The resulting, novel vertex algebras have interesting
mathematical properties and can be used to make nontrivial predictions about
the low energy limits of these SCFTs. Based on joint work with C. Beem, arXiv:2201.13435
Praxitelis Ntokos
(Edinburgh): On the
uniqueness of supersymmetric AdS_5 black holes with toric
symmetry
In this talk, I will describe recent progress on the
classification of supersymmetric AdS_5 black holes to minimal gauged supergravity.
For solutions with a torus symmetry, this classification reduces to a problem
in toric Kahler geometry which is most conveniently
formulated in terms of a symplectic potential. The
singular behaviour of the latter at the boundary of the orbit space encodes the
horizon and axis structure of any possible BPS black hole spacetime within the toric class. I will also present the first uniqueness
theorem(s) for supersymmetric AdS_5 black holes: any supersymmetric and toric solution that is timelike
outside a smooth horizon, with a Kahler base metric of Calabi
type, must be the BPS limit of the (Chong, Cvetic,
Lu, Pope) CCLP black hole solution or its nearhorizon geometry, based on arXiv: 2208.00896
Enrico Parisini
(Southampton): An embedding
formalism for CFTs in general backgrounds and states
Conformal field theories exhibit a high level of control provided
by conformal symmetry. However, in many relevant situations conformal symmetry
is broken by either the state or the background of the theory, and most of the
mathematical control is lost. In this talk I will present a framework
generalising the embedding space formalism to compute the observables of CFTs
in nontrivial states and on generic backgrounds. In this construction (d+2)dimensional
Minkowski is replaced by a more general Ricciflat
metric, the ambient space by Fefferman and Graham. As
an example, I will apply this formalism to the case of 2point functions in
CFTs at finite temperature. I will also comment on the relations with flat
holography.
Maxim Trepenier
(KCL): Bootstrapping
string dynamics in the 6d N = (2, 0) theories
The 6d (2, 0) theories are superconformal field theories believed to describe the
lowenergy dynamics of N coincident M5branes. These theories don‚Äôt have a known lagrangian
description and remain largely mysterious, so it is an interesting question how
one might calculate observables there. In this talk I will present two
complementary approaches to a case study, the calculation of the 2point function
of stress tensors in the presence of a 1/2 BPS surface defect defined over a
plane. First, we use analytical bootstrap techniques at large N to obtain the
first nontrivial correction to this correlator, from which we extract the
defect CFT (dCFT) data characterising the 2d dCFT
of the 1/2 BPS plane. Along the way we derive a supersymmetric inversion
formula and obtain the relevant superconformal
blocks. Notably our result features a holomorphic function whose appearance is
related to the chiral algebra construction of Beem et
al. Second, we use that chiral algebra description to obtain exact results for
the BPS sector of the dCFT, valid at any N and for
any choice of surface operator. The setup we present here is remarkably simple
and the same techniques can be applied to many more nonlagrangian
theories.
Thomas Bartsch (Durham): Noninvertible
symmetries and higher representation theory
Andrea Boido
(Oxford): A
gravitational block formula for spindle geometries
David Bonomi (City): Analytic bootstrap
for defect CFTs
Calvin Chen (IC): Causality and
Gravitational EFTs
Arpit Das
(Durham): Chiral
magnetohydrodynamics, Symmetries and Holography
Mang Hei
Gordon Lee (Cambridge): Analytic
Structure of Wavefunction Coefficients
Suvajit Majumder (City): Protected states and
excited state TBA in AdS3xS3xT4
Rishi Mouland (Cambridge): Black Hole Entropy
from Quantum Mechanics
James Pearson (Durham): Noninvertible Symmetries
and Higher Representation Theory
Torben Skrzypek
(Imperial): Integrability
of type 0 and other Orbifolds of AdS5xS5