fpuk

First Virtual Meeting 7-8 January 2021

events

 

 

Orangizers: D. Berman, J. Gauntlett, T. Hollowood, N. Lambert, S. Ross, S. Schafer-Nameki, M. Taylor and D. Tong

 

 

 

Schedule:

 

	January 7th	January 8th
14:00	Apruzzi	Nagy
14:30	Poovuttikul	Legramandi
15:00	Lohitsiri	Prohazka
15:30	Break	Break
16:00	Gong Show	Crichigno
16:30	Poster Session	Galante
17:00	Poster Session	Withers
17:30	Wine and Cheese Reception

 

Note that at 18:00 on the 8^th there is a public online talk in honour of Stephen Hawking.

 

Talks:

 

Fabio Apruzzi (Oxford): The fate of discrete 1-form symmetries in 6d. 

 

Abstract: In this talk I will focus on 1-form symmetries of 6d supersymmetric gauge theories coupled to dynamical tensor multiplets. In a non-trivial background for the global 1-form symmetry, the low-energy theory partition function is ambiguous under large gauge transformation for the tensor fields. This anomaly is eliminated by the inclusion of BPS strings. However, the non-trivial 1-form symmetry background can induce fractional string charges which are not compatible with Dirac quantization. In this case the symmetry is absent. I will describe how the anomalous term serves as a tool to detect whether the discrete 1-form symmetries are realised in explicit examples originating from string theory compactifications. This is also corroborated by the presence of states, which are excitations of the 6d BPS strings and explicitly break the global 1-form symmetry. For 6d theories consistently coupled to gravity, this ambiguity of the partition function hints at the presence of a symmetry breaking tower of states. When the ambiguity is absent, the F-theory realisation of the theories points to the gauging of the 1-form symmetries.

 

Marcus Crichigno (Imperial): Supersymmetry and Computation

 

I will discuss some aspects on the interplay between supersymmetry and the theory of classical and quantum computation.

 

Damian Galante (KCL): De sitter horizons and holography

 

Observers in a de Sitter spacetime are surrounded by a cosmological event horizon. Even though its thermodynamic properties have been proposed long time ago, its microscopic origin remains elusive. In this talk I will describe recent progress towards understanding the emergence of cosmological horizons in the context of holography in two spacetime dimensions, both from a macro and a microscopic perspective.

 

Andrea Legramandi (Swansea): Extracting information from Hawking radiation

 

Recently, it has been discovered that semiclassical evaporating black holes can still evolve unitarily and reproduce the Page curve if a notion of entropy which includes the contribution of the so-called "island" is considered. Such islands start to dominate at late times and encode part of the black-hole interior in the early radiation. I will show that, in the JT-gravity framework, a plethora of islands appears depending on which subset of Hawking radiation is considered, leading to various competing entropy saddles. I will discuss how these results allow for a detailed analysis of the Hawking-radiation correlation confirming several hypotheses and conjectures, such as the A=R_B scenario and the Hayden-Preskill information-recovery protocol.

 

Nakarin Lohitsiri (Cambridge): Anomaly Interplay in U(2) Gauge Theories

 

In this talk I will discuss anomaly cancellation in U(2) gauge theories. Because the fifth spin bordism group of BU(2) vanishes, there should be no global anomaly in contrast with gauge group SU(2). I will show explicitly that the usual global anomaly in SU(2) is replaced by a local one when SU(2) is embedded in U(2). 

 

Silvia Nagy (QMUL): From symmetries to generalised double copy rules

 

I will give an overview of recent results in the derivation of gravitational symmetries from Yang-Mills symmetries, and how they inform the construction of solutions and Lagrangians via the double copy. I will also present a double copy construction of asymptotic symmetries, and some surprising new lessons one can learn from the self-dual sector.

 

Nick Poovuttikul (Durham): Holography and hydrodynamics of higher-group symmetry

 

Higher-form symmetry associated to extended operators are ubiquitous in quantum field theory. Together, these generalised global symmetry can be combined and form a larger structures known as higher-group. I will give a review of recent developments of hydrodynamic descriptions that describe QFTs with higher-form and higher-group (particularly 2-group) global symmetry in the deep IR. I will also discussed key features of minimal holographic model constructed from higher-form/higher-group gauge theory in the bulk and how it captures universal predictions from hydrodynamics. 

 

Stefan Prohazka (Edinburgh): Limits of JT gravity

 

Jackiw–Teitelboim gravity has been at the center of various recent advances in high energy physics (information paradox, matrix models, ...). Since it is based on anti-de Sitter space, a maximally symmetric lorentzian spacetime, one might wonder if there exist similar theories of flat, galilean and carrollian origin. We will answer this question in the affirmative and provide boundary graviton effective actions analog to the Schwarzian. I will comment on numerous applications and generalizations.

 

Benjamin Withers (Southampton): Holography and convergence of the hydrodynamic series

 

I will give a brief overview of recent developments in large-order relativistic hydrodynamics using properties gleaned from holographic theories. I will show that quasinormal mode dispersion relations, expanded for small momentum, have a finite radius of convergence set by a branch point singularity in the complex momentum plane. The location of this singularity is an intrinsic property of the microscopic theory under consideration, and once computed, gives rise to a precise condition on initial data for the convergence of the hydrodynamic expansion of its energy-momentum tensor, for arbitrary linear deviations from equilibrium.

 

Gong Show and Posters:

 

Mohammad Akhond (Swansea): Factorised 3d N=4 orthosymplectic quivers

 

We study the moduli space of 3d N = 4 quiver gauge theories with unitary, orthogonal and symplectic gauge nodes, that fall into exceptional sequences. We find that both the Higgs and Coulomb branches of the moduli space factorise into decoupled sectors. Each decoupled sector is described by a single quiver gauge theory with only unitary gauge nodes. These quivers serve as magnetic quivers for 5d N = 1 SCFTs which can be engineered in type IIB both with and without an O5 plane. We use the two constructions to postulate the dual pairs of unitary and orthosymplectic quivers by deriving them as magnetic quivers of the 5d theory. A non-trivial test of this proposal is the agreement between the Hilbert series computations on both sides.

 

Roland Bittleston (Cambridge):  Twistors, integrability, and 4d Chern-Simons theory

 

I will relate approaches to classical integrable systems via 4d Chern-Simons theory and via symmetry reductions of the anti-self-dual Yang-Mills equations. To achieve this I will obtain both from holomorphic Chern-Simons theory on twistor space, defined using a range of meromorphic (3,0)-forms.

 

Mathew Cheung (Oxford):  Spatially modulated and supersymmetric mass deformations of N=4 SYM

 

Mass deformations of 4d N=4 SYM theory that preserve some supersymmetry have been extensively studied and are associated with rich dynamical features under RG flow. Recently, we have studied mass deformations of N=4 SYM theory that are spatially modulated in one of the three spatial dimensions and still preserve some supersymmetry. Moreover they can preserve 3d conformal symmetry associated with a co-dimension one interface.  We construct rich classes of holographic solutions, including new Janus solutions, the first RG interface solutions (i.e. with different CFTs on either side of the interface) and a new supersymmetric AdS4xS1xS5 solution of type IIB supergravity. This is based on the work hep-th/2007.07891 and hep-th/2007.15095 with Igal Arav, Jerome Gauntlett, Matt Roberts and Chris Rosen.

 

Ed Hirst (City): Dessins d’Enfants & Machine-Learning

 

Dessins d’Enfants will be introduced, which are useful tools in both Galois theory and analysis of quiver gauge theories. Following this, work performed to classify a database of dessins d’enfants according to their Galois orbit size using machine-learning will be discussed.

 

Saghar Sophie Hosseini (Durham): Higher form symmetries of geometrically engineered field theories

 

I will discuss my research on the geometric origin of higher form symmetries of quantum field theories. These symmetries may be found systematically in terms of the defect groups from geometric engineering in various string theories. The flux non-commutativity in string theory gives rise to (mixed) 't Hooft anomalies for the defect group which constrains the corresponding global structures of the associated quantum fields.

 

Tommaso Macrelli (Surrey): The L-infinity origin of scattering amplitudes recursion relations

 

Higher algebraic structures are ubiquitous in fundamental physics. For instance, $A_{\infty}$- and $L_{\infty}$-algebras emerge in the context of string field theory. Importantly, via the Batalin-Vilkovisky formalism, any Lagrangian field theory admits an $L_{\infty}$-algebra that governs all of its physics including field equations, symmetries, and Noether identities. In the talk and in the poster session, I will explain the connection between higher algebraic structures and scattering amplitudes. In particular, I will prove that powerful recursive methods, such as the Berends-Giele gluon scattering recursion relation, emerge very naturally and straightforwardly in any Lagrangian field theory when using the $L_{\infty}$-algebra language.

 

Rishi Mouland (Kings): Exotic 5d Correlators and 6d (S)CFTs

 

I will present an outline of recent work investigating five-dimensional field theories with an SU(1,3) symmetry, in particular demonstrating the symmetry’s power in constraining correlators. The utility of these theories in the construction of 6d CFTs will be discussed, along with an explicit Omega-deformed Lagrangian example expected to lift to the (2,0) theory. During the poster session, I will contextualise these results within M-theory (in particular the DLCQ proposal for the M5-brane), and within the AdS7/CFT6 correspondence.

 

Dominik Rist (Heriot-Watt): Towards an M5-Brane Model

 

I will present recent progress in constructing a six-dimensional N = (1, 0) supersymmetric higher gauge theory in which self-duality is consistently implemented by physically trivial Lagrange multipliers. Our action contains both N = (1, 0) tensor and vector multiplets and is non-trivially interacting. The tensor multiplet part is loosely related to a recently proposed action by Sen that leads to on-shell self-duality in an elegant way. This talk is based on our recent paper arXiv:2012.09253v1.

 

Paul Rodgers (Southampton): Hairy black holes and solitons in a Minkowski box.

 

Reissner-Nordstrom black holes (RN BH's) are stable to linearised scalar and gravitoelectromagnetic perturbations. However, if one were to place a confining box/mirror around the RN BH and probe again with linear perturbations (we consider a charged scalar field), the system can be driven unstable for certain values of the scalar field charge. This is the charged BH version of Press and Teukolsky's "rotating BH bomb". Numerical time evolutions indicate that the endpoint of these instabilities is described by a charged black hole with scalar hair. Based on the above observations, perturbative constructions of these hairy solutions have been carried out which are only valid for small energies/charges. Motivated by this we study the solutions to the full, non-linear Einstein-Maxwell-scalar field theory by numerically solving the equations of motion. I will summarise and illuminate key features of the phase diagram, which depends sensitively on the scalar field charge.

 

Maximilian Ruep (York): Weakly coupled local particle detectors cannot harvest entanglement

 

Entanglement harvesting is the process in which two particle detectors, initially in an uncorrelated product state, (e.g. two Unruh detectors in their respective Gaussian pure ground states) are coupled to a quantum field in two spacelike separated regions and end up in an entangled final state. Due to the intrinsic non-relativistic nature of, for instance, the Unruh detector, the coupled structure is non-local. In this gong show and poster session I will explain the notion of local particle detectors, given by a local Bosonic mode of a scalar probe field (a proxy for a truly local measurement

device) and I will show that they cannot harvest entanglement at weak coupling when initially prepared in a physically reasonable state.

 

Andreas Schachner (Cambridge): Systematics of higher-derivative terms in F/M-theory compactifications

 

In this talk, I summarise a project in collaboration with M. Cicoli, F. Quevedo, R. Savelli and R. Valandro. The main open technical problem to extract EFTs for string compactifications is deriving corrections to the tree level supergravity actions. Even though progress has been made over the years, a systematic approach has not yet emerged. From a low energy perspective, perturbative corrections to the Kähler potential have a direct impact on moduli stabilisation simply because the scalar potential vanishes at tree level due to a no-scale property. To this end, we systematically analyse α′-effects in F-theory from higher-derivative terms in M-theory utilising the impressive machinery of string dualities. Applying an approach based on a parametric volume scaling analysis, we claim that conventional Kaluza-Klein reductions on elliptically fibered Calabi-Yau fourfolds can only give rise to (α′)even-corrections. Furthermore, we argue that all contributions from 8-derivative terms in the M-theory action vanish upon compactification on a trivially fibered fourfold. Since (α′)odd-effects play a dominant role in moduli stabilisation of type IIB/F-theory, new techniques are required for recovering them.

 

Marieke van Beest (Oxford): 5d Higgs Branches in the Tropical Rain Forest

 

We derive the structure of the Higgs branch of 5d SCFTs from their realization as a generalized toric polygon (GTP). The Higgs branch is accessed by a refined Minkowski sum decomposition of the GTP, generalizing the decomposition that determines the deformation space of strictly convex toric polygons. Analogously to the dual brane-web description, we compute the magnetic quiver that encodes the Higgs branch of 5d SCFTs  from this decomposition. In a 5d SCFT, successive decoupling of hypermultiplet matter and RG-flow generates a tree of descendant SCFTs. Decoupling in a GTP straightforwardly generalizes standard flop transitions of curves in toric polygons. We apply this approach to a large class of 5d KK-theories, and determine the magnetic quiver and Hasse diagram, that characterise the Higgs branch, for entire descendant trees, in particular for all rank 2 5d SCFTs. For each tree, we also identify the flavor symmetry algebras from the magnetic quivers, including non-simply-laced flavor symmetries.

 

Daniel Zhang (Cambridge): Boundaries, Vermas and Factorisation in 3d N=4 Theories

 

I will discuss a recent work on the factorisation of closed 3-manifold partition functions and indices of 3d N=4 gauge theories. The building  blocks are hemisphere partition functions equipped with a class of UV  N=(2,2) boundary conditions that mimic the presence of isolated vacua at infinity. Via the state-operator correspondence, these count local operators supported on a (2,2) boundary condition on a plane. A subset of these operators are boundary Higgs and Coulomb branch operators, which form lowest weight Verma modules over the quantised bulk Higgs and Coulomb branch chiral rings. We show that certain limits of the hemisphere partition functions compute their characters. We find that the equivariant supersymmetric Casimir energy encodes the boundary ’t 
Hooft anomaly, and also plays the role of highest weights. Applying these results to factorisation then leads to various “IR formulae” for partition functions on closed 3-manifolds in terms of these Verma characters. This talk is based on a work 2010.09741 in collaboration with M Bullimore and S Crew.

 

Zhenghao Zhong (Imperial): SCFTs and Magnetic Quivers

 

Magnetic quivers has proven to be a useful tool in exploring the geometry of Higgs branches for supersymmetric gauge theories . In this gong show, I will discuss how magnetic quivers can be used to explore the Higgs branch of 4d N=2 and 5d N=1 SCFTs.