fpuk

Semi-In-Person Meeting 13 November 2021

events

 

 

Organisers: D. Berman, J. Gauntlett, P. Kumar, N. Lambert, S. Ross, S. Schafer-Nameki, M. Taylor and D. Tong

 

Tentative Schedule:

 

	November 13th
09:30	Registration
10:00	Cabo-Bizet
10:30	Roberts
11:00	Tennyson
11:30	Break
12:00	Legramandi
12:30	Gong Show
13:00	Lunch
14:00	Poole
14:30	Nguyen
15:00	Capone
15:30	Break
16:00	Bonneti
16:30	Hwang
17:00	End

 

The presentations will be held in the Safra Lecture Theatre in the main Strand Campus of King’s College London.

 

Refreshments and lunch will be provided and taken in the Great Hall.

 

You will also be expected to abide by the King’s College COVID rules including wearing a mask and social distancing:

 

https://www.kcl.ac.uk/coronavirus/campus

 

Talks:

 

Federico Bonetti (Oxford): Holographic Duals of Argyres-Douglas Theories (video)

Superconformal field theories (SCFTs) of Argyres-Dougles type are inherently strongly coupled and provide a window onto remarkable non-perturbative phenomena (such as mutually non-local massless dyons and relevant Coulomb branch operators of fractional dimension). In this talk, I will discuss the first explicit proposal for the holographic duals of a class of SCFTs of Argyres-Douglas type. The theories under examination are realised by a stack of M5-branes wrapped on a sphere with one irregular puncture and one regular puncture. In the dual 11d supergravity solutions, the irregular puncture is realised as an internal M5-brane source.

 

Alejandro Cabo-Bizet (King’s): Zero-temperature topological order in 4d SU(N) N=4 SYM (video)

 

We argue that under certain conditions, 4d SU(N) N=4 SYM exhibits zero-temperature topological order. The topological phases are characterized by the condensation of N bound states, each of them composed of two Dyonic surface operators/states. The bound states form an N-dimensional representation of a Z_N one-form global symmetry transformation. Effectively, they can be understood as the physical degrees of freedom of SU(N)_1/SU(N)_1 WZNW model on a two-torus.

 

Frederico Capone (Southampton): The problem of BMS superrotations in higher dimensions and flat holography (video)

 

Paths to build holographic descriptions of asymptotically flat spacetimes are fuelled by the discovery that the asymptotic BMS symmetries of such spacetimes are related to well-known Weinberg soft scattering theorems. New subleading soft theorems have been discovered assuming that the BMS symmetries are extended to include superrotations. The scattering theorems have been proven to hold in any number of spacetime dimensions greater or equal than four. On the other hand, the role of (the extensions of) BMS symmetries in higher dimensional gravity is poorly understood. We derive the most general set of boundary conditions that would allow for appropriate generalisation of the extended BMS symmetries. This necessarily requires an extension of the definition of asymptotic flatness. We discuss how this relates to the scattering problem and to a holographic viewpoint.

 

Chiung Hwang (Cambridge): Rethinking mirror symmetry as a local duality on fields (video)

In this talk, I will discuss novel aspects of 3d mirror symmetry and its 4d generalisation for linear quiver gauge theories. I will first introduce a family of new 4d N=1 IR dualities that, in a suitable 3d limit, reduce to mirror symmetry for unitary gauged linear quiver theories. One notable example of such 3d quivers is the so-called T[SU(N)] theory, which is self-mirror and also known to be associated with the S-duality domain wall in the 4d SU(N) SYM theory. Motivated by this, we claim that the 4d counterpart of T[SU(N)], called the E[USp(2 N)] theory, can be identified as a 4d version of the S-wall. Furthermore, such S-wall interpretations of T[SU(N)] and E[USp(2N)] lead to an intriguing algorithm translating mirror symmetry into a combination of local dualities acting on elementary fields. Remarkably, all the dualities used in this algorithm can be derived from a single fundamental Seiberg-like duality, which reveals a deep connection between mirror and Seiberg-like dualities.

 

 

Andrea Legramandi (Swansea): Island in the stream of Hawking radiation (video)

 

We consider the island formula for the entropy of an arbitrary subset of the Hawking radiation in the adiabatic limit, including the effect of a grey-body factor. We find a simple concrete ‘on-shell’ formula for the generalized entropy which involves the image of the island out in thestream of radiation, the ‘island in the stream’.

The grey-body factor allows us to analyse the role of irreversibility in the evaporation. In particular, we show that irreversibility leads to multiple saddles to dominate the entropy, and we will match this result with a generalization of Page's theorem that involves a nested temporal sequence of unitary averages.

 

Nam Nguyen (Durham): Metastable Antibranes (video)

 

Despite their consequential applications, certain aspects of metastable state of antibranes in warped throats are not yet fully understood. In this talk, I will introduce the Kachru-Pearson-Verlinde (KPV) state, a frequently-discussed exemplar metastable antibranes configuration, and briefly recap the decade-long discussions on its existence. I will ``premiere'' (soon-to-appear in an upcoming publication) an approximate supergravity description for the KPV state. This perturbative description is obtained via matched asymptotic expansion and approximates the KPV configuration when there is a large separation of scale, i.e. when the length scale associated to the branes is much smaller than the length scale associated to the background/bending. I'll discuss how this approximate solution, taken in conjunction with previous results, serves as ``conclusive'' evidence in the discussion on the existence of the KPV state. If time permits, I will also introduce discussions on classical stability and discuss how our result can provide insights there.

 

Aaron Poole (Southampton): Charges and fluxes in de Sitter Space  (video)

In this talk I will discuss conserved quantities in asymptotically locally de Sitter (dS) spacetimes. I will begin by motivating this work within the aim of developing a framework for gravitational waves in dS for full nonlinear general relativity. I will then review the asymptotics of dS spacetimes, before showing that one can use the tools of the covariant phase space formalism, together with techniques from AdS/CFT, to derive expressions for conserved quantities. I will present flux formulae which capture the effects of outgoing gravitational radiation, illustrated via application to exact solutions of the field equations. This talk is based on work in collaboration with Kostas Skenderis and Marika Taylor.

 

Matt Roberts (Imperial): Bending graphene and curved space Dirac

 

Monolayer graphene, with its infrared spectrum of massless Dirac particles, naturally bends and ripples, providing a laboratory for realising three-dimensional field theories in curved space. We construct an explicit continuum limit of the lattice model of graphene in real space, which is non-linear in hopping strengths, which leads to a continuum Dirac equation in curved space coupled to a vector potential given by the lattice strain. We find that a finite continuum vector potential requires that the anisotropy of tunnelling amplitudes vanishes linearly in the lattice spacing. We find a Weyl flat metric in the lattice coordinates, independent of strain applied, along with the strain gauge field. Often in continuum descriptions of graphene it is assumed that the metric the Dirac fields couple to is the same as the induced metric on the graphene membrane, but we find this is not generally the case. If we assume our tight-binding model is embedded in flat space, and the tunnelling amplitudes depend only on inter-atomic distances, we derive a non-linear relation between the embedding metric and the electro-metric, which we emphasise may be very different for appreciable bending. 

 

David Tennyson(Imperial): Topological strings at 1-loop from double complexes

 

The topological A/B-model have been an important tool for studying both string theory and the geometry of Calabi-Yau manifolds. They provide both new geometric invariants of the Calabi-Yau, as well as calculating certain terms in the effective theory of string theory. While topological strings on other special holonomy manifolds have been postulated, they are far less understood. In my talk, I will examine the topological string on G2 and Spin(7) manifolds from the target space perspective. I will show that any special holonomy manifold has a double complex which generalises the Dolbeault complex of Calabi-Yau manifolds and provides the natural candidate for the BRST complex of the topological string. Through this, I will be able to identify the cohomology of operators and calculate the 1-loop partition functions of the G2 and Spin(7) topological strings.

 

Apologies for the missing videos due to the internet failure.

 

Gong Show and Posters (Video):

 

Mohammad Akhond (Swansea):  Electrostatic description of 3d N=4 linear quivers

 

I will discuss the holographic duals of the IR fixed points of 3d N=4 linear quivers. I will use the holographic language to calculate various field theory quantities. In particular we will show how the holographic central charge computation matches the field theory calculation of the free energy. I will then show how mirror symmetry is realised in the holographic language.

 

Adam Chalabi (Southampton): Central Charges of Conformal Defects

 

In this talk I will explain how conformal defects can be characterised by their contributions to the trace anomaly of the stress tensor. I will give examples of 2d conformal defects where the trace anomaly can be computed exactly, without requiring any approximations or limits. I will discuss a simple example in free field theories. In another set of examples, I will explain how supersymmetry allows for straightforward computation of defect central charges in interacting conformal field theories. Finally, I will discuss some work in preparation on 4d conformal defects in which we determine the general form of the defect trace anomaly and study various examples.

 

Ziwen Kong (King’s): Conformal and Nonconformal Hyperloops

 

My poster is based on work in progress with Nadav Drukker, Malte Probst, Marcia Tenser and Diego Trancanelli. We present new circular Wilson loops in three-dimensional N = 4 quiver Chern-Simons-matter theory on S^3. We follow and further develop a method of finding new supersymmetric Wilson loops by starting from an operator known to preserve some supercharges, then add a deformation such that the resulting Wilson loops share at least one supercharge with the original operator. In our work we take as the starting point a 1/2 BPS operators, rather than the 1/4 BPS bosonic Gaiotto-Yin loops in the previous work. Having more supercharges to deform with results in many more new moduli spaces of loop operators. In particular, we find new supersymmetric Bosonic loops including some preserving 3 supercharges. We also find a new family of 1/4 BPS Fermionic loops that are not conformal.

 

Suvajit Majumder(City): Protected states in AdS3 backgrounds from integrability(based on 2103.16972)

 

We discuss a new method to construct the zero-momentum limit of Bethe states within the framework of algebraic Bethe ansatz, that is used to compute the protected spectrum in various AdS3 backgrounds. We get results consistent with SUGRA,CFT computations at special points of the moduli space, but hold true in much more generality(across entire moduli spaces).

 

Arshia Momeni(Imperial): Massive Double Copy in D=4

The double copy has been found to be more general than the relationship between Yang-Mills theory and gravity amplitudes. There are known examples of extensions of double copy relations between two non-gravitational theories for example non-linear sigma model and special Galileon theories as well as extended gravitational relations such as that between super Yang-Mills and supergravity theories. Almost all these developments are well established for massless theories, while the double copy for massive theories is far less understood. In this presentation, I will describe the recent application of the double copy to the scattering amplitudes of massive Yang-Mills theory.

 

Tristan Orchard (King’s):  A Path Integral for the Chiral Form Partition Function

 

Recently Sen made a prescription to form action princples of self dual forms in 4n + 2 dimensions by implementing two metrics in the action, one physical and one unphysical and invariant under diffeomorphisms. These actions have the undesirable property of non-unitarity of one of the scalar fields, which conveniently separates out in the Hamiltonian formalism. In this work we wick rotate the physical metric only, and leave the unphysical metric alone, to achieve a convergent path integral in the Lagrangian picture. Our result reproduces many desirable and historically important results when applied to the classic example of the 2d chiral boson. Giving  \Theta/ \eta without the need for holomorphic factorisation. Work to appear shortly with E. Andriolo ,N. Lambert, T. O and C. Papageorgakis

 

Sergei Ovchinnikov (Edinburgh): Uniqueness of supersymmetric black holes in AdS5

 

The classification of anti de Sitter black holes is an open problem of central importance in holography. In this talk, I will present new advances in classification of solutions to five-dimensional minimal gauged supergravity. In particular, we prove a black hole uniqueness theorem for supersymmetric solutions with SU(2) symmetry and an analytic horizon, which shows that the Gutowski-Reall black hole is the only solution in this class. We also show that a class of supersymmetric solitons with SU(2) symmetry and a bolt possess an enhanced U(1)xSU(2) symmetry, and we exhibit a family of asymptotically AdS5/Zp solitons for p ≥ 3  of this type.

 

Justinas Rumbutis (Imperial): Massive Double Copy in D=3

 

Recently found difficulties in looking for double copy relations between massive Yang-Mills and massive gravity theories in D=4 led to exploration of double copy in lower dimensions. It was found that in D=3 topological massive Yang-Mills can be double copied to topological massive gravity. This double copy formalism in D=3 has some unusual features, for example, the form and the number of BCJ relations can be different from that in D>3. In this presentation I will describe this massive double copy formalism in D=3 and how it can relate topological massive gauge and gravity theories.

 

Andreas Schachner (Cambridge) : The Standard Model Quiver in de Sitter String Compactifications

With the advent of the string landscape, the realisation of the Standard Model in general string theory compactifications to 4D has become a primary focus. This talk concerns novel constructions of the Standard Model in global set-ups of type IIB Calabi-Yau compactifications. We argue that the Standard Model quiver can be embedded into compact Calabi-Yau geometries through orientifolded D3-branes at del Pezzo singularities dP_n with n ≥ 5 in a framework including moduli stabilisation. To illustrate our approach, we explicitly construct a local dP_5 model via a combination of Higgsing and orientifolding. This procedure reduces the original dP_5 quiver gauge theory to the Left-Right symmetric model with three families of quarks and leptons as well as a Higgs sector to further break the symmetries to the Standard Model gauge group. We embed this local model in a globally consistent Calabi-Yau flux compactification with tadpole and Freed-Witten anomaly cancellations. The model features closed string moduli stabilisation with a de Sitter minimum from T-branes, supersymmetry broken by the Kähler moduli, and the MSSM as the low energy spectrum. We further discuss phenomenological and cosmological implications of this construction.

 

Jake Stedman (King’s): Four-Dimensional Chern-Simons Theory and Gauged Sigma Models

Several years ago, a new gauge theory called four-dimensional Chern-Simons was introduced by Costello in an attempt to explain the integrability of various two-dimensional models using techniques in gauge theory. My work focuses on the use of four-dimensional Chern-Simons to explain the integrability of two-dimensional sigma models. I will begin by reviewing the construction of the Wess-Zumino-Witten (WZW) model as the boundary theory of three-dimensional Chern-Simons theory as was introduced by Moore and Seiberg. This will allow me to introduce the analogous construction of Costello and Yamazaki, in which two-dimensional sigma models appear as theories on defects in four-dimensional Chern-Simons. This naturally leads to a discussion of my work in which I construct a large class of gauge sigma models by coupling together two four-dimensional Chern-Simons theories. I will argue that the structure of four-dimensional Chern-Simons suggests that these models are integrable. I will finish by constructing the gauged WZW model and conformal Toda theories. This is based on research in: https://arxiv.org/abs/2109.08101.

 

 

Zhenghao Zhong (Imperial): Higgs branches of U/SU Quivers via Brane Locking

 

We solve a long standing problem on the computation of the Higgs branch of linear quivers with 8 supercharges with both unitary and special unitary gauge groups. The solution uses the idea of magnetic quivers where the  Higgs branches are described as 3d N=4 Coulomb branches. The magnetic quivers are obtained from studying the brane web for an auxiliary 5d theory, constrained by a new notion called brane locking where a set of branes are forced to move together. If the starting quiver is good, the magnetic quiver is also the 3d mirror and we extend the analysis to include non-linear quivers as well, thus allowing us to construct a very large family of new 3d mirror pairs.