UEATLecture Theatre 2
FIRST seminar
SECOND seminar
2023-05-24Pre-seminarA session during which speakers will give a short introduction to their talks for PhD students and postdocs. TBATBA2023-05-10Pre-seminarA session during which speakers will give a short introduction to their talks for PhD students and postdocs. Benoit VicedoUniversity of YorkTBATBA2023-04-26Pre-seminarA session during which speakers will give a short introduction to their talks for PhD students and postdocs. Olalla Castro-AlvaredoCity College LondonTBATBA2023-04-12Pre-seminarA session during which speakers will give a short introduction to their talks for PhD students and postdocs. Koenraad SchalmLeidenTBAMichele del ZottoUppsalaTBA2023-03-15Pre-seminarA session during which speakers will give a short introduction to their talks for PhD students and postdocs. Bernardo AranedaAEI GolmTBACeline ZwikelPerimeter InstituteTBA2023-03-01Pre-seminarA session during which speakers will give a short introduction to their talks for PhD students and postdocs. Dionysios AnninosKing's College LondonTBAFridrich ValachImperial College LondonTBA2023-02-01 Matthew WaltersEPF Lausanne, University of GenevaQFT Dynamics from CFT DataWhile quantum field theory has given us a successful description of physical phenomena at many different length scales, almost all computations are currently limited to systems which are weakly-coupled or have large amounts of symmetry. I will present a new theoretical framework for solving general strongly-interacting QFTs, which uses data from UV fixed points (i.e. conformal field theories) to numerically compute QFT observables. This approach uses low-dimension operators from the UV CFT to approximate the low-energy eigenstates of the full QFT Hamiltonian, allowing us to study dynamics even at strong coupling. After presenting a general framework which can be applied to QFTs in any number of dimensions, I will then discuss its application to multiple strongly-coupled systems, focusing in particular on recent results studying non-equilibrium dynamics at finite temperature and the computation of nonperturbative scattering amplitudes.2023-01-25Pre-seminarA session during which speakers will give a short introduction to their talks for PhD students and postdocs. Luca DelacretazUniversity of ChicagoNonlinear Effective Field Theory of Fermi LiquidsLandau's theory of Fermi liquids is a cornerstone of theoretical physics. I will show how to formulate Fermi liquid theory as an effective field theory of bosonic degrees of freedom, using the mathematical formalism of coadjoint orbits. While at the linear level, this theory reduces to existing multidimensional bosonization approaches, it necessarily features nonlinear corrections that are fixed by the geometry of the Fermi surface. These are crucial to reproduce nonlinear response, such as higher-point functions of currents. The effective field theory framework furthermore systematically parametrizes corrections to Fermi liquid behavior, and provides a computationally advantageous approach for non-Fermi liquids -- strongly interacting fixed points obtained by deforming Fermi liquids with relevant interactions.Peter CameronUniversity of EdinburghCausal Structure at Infinity and the Positive Mass TheoremA spacetime is said to satisfy the Penrose property if every pair of points on past and future null infinity can be connected by a timelike curve. Penrose showed that this property fails in Minkowski spacetime of any dimension but is satisfied in 3+1 dimensional positive mass Schwarzschild. I will consider the Penrose property in more detail and discuss how it is related to the ADM mass and dimensionality of the spacetime. I will then show how some of the ideas arising in the study of this property can be used to prove a version of the positive mass theorem. Finally, I will discuss how the apparent failure of the Penrose property in higher dimensions (regardless of the ADM mass) may be linked to the greater regularity of possible conformal completions of the spacetime at spacelike infinity.Bayes CentreICMS Lecture Theatre2022-12-14Pre-seminarA pre-seminar is a session during which speakers will give a short introduction to their talks. Arpit DasDurham UniversityChiral magnetohydrodynamics, Symmetries and HolographyIn this talk, we will discuss QED at finite temperature from a hydrodynamic viewpoint. In the first part of the talk we shall discuss the symmetries of QED using the notion of higher-form symmetries. In the second part of the talk, we will discuss a holographic model which has the same higher-form symmetry structure. We will also very briefly touch upon work in progress regarding an effective hydrodynamic description of QED at T>0, using non-invertible symmetries. Peter SchuppJacobs University BremenFree fall in graded geometry (interaction via deformation)Deformations of the algebra of quantum operators lead to a description
of fundamental interactions that generalizes (and in a sense unifies)
the principles of gauge theory and the geometric description of gravity
as free fall in curved spacetime. This is quite well established for
electromagnetism and is for example useful for the description of
charged particles in a magnetic monopole background. We shall show that
also gravitational interactions find such an algebraic description, but
the construction requires a graded geometry setting. The construction
suggests a novel somewhat more algebraic interpretation of key
ingredients of general relativity. Generalized Geometry arises in this
context via the derived bracket formalism and yields a symmetry-based
approach to string effective gravity actions. Further examples of
applications of graded geometry and deformation methods in (quantum)
field theory include e.g. non-commutative gauge theory, tensor gauge
theories, non-local interactions.
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Bayes CentreICMS Lecture Theatre2022-11-30Pre-seminarA pre-seminar is a session during which speakers will give a short introduction to their talks. Romain RuzziconiVienna University of TechnologyFlat Space Holography: From Carrollian to Celestial AmplitudesThe flat space holography program aims at describing quantum gravity in asymptotically flat spacetime in terms of a dual lower-dimensional field theory. Two different roads to construct flat space holography have recently emerged. The first consists of a 4d bulk / 3d boundary duality, called Carrollian holography, where 4d gravity is suggested to be dual to a 3d Carrollian CFT living on the null boundary of the spacetime. The second is a 4d bulk / 2d boundary duality, called celestial holography, where 4d gravity is dual to a 2d CFT living on the celestial sphere. I will argue that these two seemingly contradictory proposals are actually related. The Carrollian amplitudes will be mapped to the celestial amplitudes using an appropriate integral transform. The Ward identities of the sourced Carrollian CFT, encoding the gravitational flux-balance laws, will be shown to reproduce those of the 2d celestial CFT, encoding the bulk soft theorems.Wei BuUniversity of EdinburghMoyal deformation, W-algebras and celestial holographyCelestial holography is the proposal of a codimension two correspondence between quantum gravity in 4d Minkowski space and some putative celestial conformal field theory on the 2d celestial sphere at the asymptotic boundary of Minkowski space. In this talk, I'll start with what the basics of the correspondence is and how the loop algebra of the wedge algebra of $w_{1+\infty}$ algebra with augmented indices emerges, then move on to review the famous family of W-algebras. After identifying the members of this family that are relevant in the context of celestial holography, I'll describe the physical theory in which W-algebra appears and its derivation. -->
Appleton TowerLecture Theatre 22022-11-16Pre-seminarA pre-seminar is a session during which speakers will give a short introduction to their talks. Abraham HarteDublin City UniversityLocalizing massless spinning objects in curved spacetimes Every textbook on general relativity states that light propagates along null geodesics. Although there are many senses in which this is true at sufficiently-high frequencies, it breaks down more generally. This talk will focus on the motion "as a whole" of electromagnetic pulses with large (but not infinitely-large) frequencies. Angular momentum then affects the motion, resulting in null but non-geodesic trajectories. Precise answers depend, however, on what exactly is meant by the "pulse as a whole": its centroid. There are many apparently-reasonable centroid definitions, but surprisingly, some of these result in positions which are nowhere near the pulse itself! This turns out to be an unphysical artifact of the fact that electromagnetic wavepackets are only approximately massless. Using this approximation uncritically turns out to result in some predictions which are not even qualitatively correct. The underlying problem is that eikonal approximations break standard features of Maxwell theory, such as the fact that exact electromagnetic stress-energy tensors satisfy positive-energy conditions.
Roger PenroseUniversity of OxfordTwistor Theory, from its origin to bi-twistors and split-octonionsTBA -->
Appleton TowerLecture Theatre 22022-11-02Pre-seminarA pre-seminar is a session during which speakers will give a short introduction to their talks. Thomas WinyardUniversity of EdinburghExotic vortex solutions in multicomponent superconductors and their experimental signaturesWhen an external magnetic field is applied to a superconductor, unlike in a normal metal, the field penetrates the material in localised flux tubes. These flux tubes can be modelled as vortex (topological soliton) solutions of an effective U(1) gauged Ginzburg-Landau (abelian Higgs) model in 2-dimensions with a complex order parameter. The solutions of this model has a rich mathematical structure and understanding their properties has interested mathematicians for several decades.
However, in the hunt for high temperature superconductivity, physicists have recently become interested in unconventional materials that exhibit a C^n order parameter. I will explore the topological soliton solutions of these unconventional models and their properties. I will then demonstrate that doubly periodic solutions exhibit peculiar magnetic structures, finally proposing experimental signatures that could be used to measure these structures in the lab.
Stefan ProhazkaUniversity of EdinburghFractons on curved space and their soft chargesFractons are quasiparticles with the distinctive feature of having only limited mobility. This bizarre trait and their unusual symmetries also make the coupling to curved spacetime nontrivial. I will highlight the underlying exotic symmetries and show how aristotelian geometry provides the right framework for placing them on curved space.
I will also emphasize that the very definition of isolated fractons requires a careful study of asymptotic symmetries. Analog to electrodynamics and general relativity, fractons have infinitely many soft charges which hint at a rich infrared structure and a fracton infrared triangle.
Based on: 2111.03668, 2203.02817, 2206.11806, work in progress -->
Appleton TowerLecture Theatre 22022-10-19Georgios PapamikosUniversity of EssexFrom set-theoretical solutions of the Yang-Baxter equation to integrable maps. Examples and generalisations.I will be discussing certain dynamical and integrability properties of certain set-theoretical solutions of the (parametric) Yang-Baxter equation. These solutions are bi-rational maps with several invariants and a Lax representation (re-factorisation of two elements of a loop group). We show that we can use these maps to construct higher dimensional bi-rational maps which admit nice properties and we prove their integrability in the Liouville sense. These maps can be seen as higher dimensional generalisations of the famous integrable QRT maps, known as Adler's Triad maps. If we have enough time, we will present two different generalisations, namely the above picture in the case of the entwining Yang-Baxter equation and also for maps with Grassmann variables.Alessandro TomasielloUniversità Milano-BicoccaSupersymmetry enhancement and the geometry of three-manifoldsModels with large supersymmetry are unrealistic, but over the years they have proven to be a very fruitful playground for improving our understanding of quantum field theory. In this talk we will consider a new class with eight supercharges in three spacetime dimensions. The simplest example gives a way to enhance the supersymmetry of a model with three Chern--Simons gauge fields (which generically only allows for six supercharges), when the inverses of the levels sums up to zero. We will also see evidence that our class arises by compactifying the mysterious six-dimensional 'M5' model on a three-manifold. Our method reproduces for example the condition for a Seifert manifold to have enhanced holonomy. More generally our class should be related to so-called graph-manifolds. The condition for enhancement is related to a jump in homology groups, and seems to suggest a non-abelian analogue of the theory of 'transversely holomorphic foliations'. -->
Appleton TowerLecture Theatre 22022-10-05Pre-seminarA pre-seminar is a session during which speakers will give a short introduction to their talks. Joaquim GomisUniversitat de BarcelonaGalilean dynamics from Carroll dynamicsWe will study the relation among Galileii dynamical systems, without extensions, and some Carroll dynamical systems. The construction of the Galilei invariant systems will be done from the knowledge of Carroll dynamical models.Bin ZhuNortheastern UniversityCelestial Amplitudes and Celestial Conformal Field TheoryIn recent years, the surprising relations between asymptotic symmetries and soft theorems have led to a promising candidate for flat holography: celestial holography. The central objects in this program are celestial amplitudes, which behave as correlation functions of primary operators in a putative conformal field theory: celestial CFT (CCFT). In this talk, we will first introduce some basics of celestial amplitudes and CCFT. We then discuss some aspects of celestial amplitudes and CCFT, including operator product expansions (OPEs), how soft theorems are related to symmetries in CCFT, and differential equations for celestial amplitudes. We will describe the recent ideas of top-down approaches in celestial holography and show one specific example, the celestial Liouville theory for Yang-Mills amplitudes. We will conclude with some open questions and future directions.