We are located at the 6th floor of the G.O. Jones Building on the Mile End Campus, midway between Stepney Green and Mile End Tube stations, approximately 1520 minutes from central London on the Central or District lines. If exiting Stepney Green tube station, turn left and walk along the Mile End Road for approximately 300 metres. The G.O. Jones (Physics) building is to the right of the main college building, which is fronted by a clocktower and lawn. If exiting Mile End tube station, turn left and walk approximately 300 metres until you are opposite the main college building. A more detailed description can be found here.
Found at least 20 result(s)
Regular Seminar Kostya Trachenko (QMUL)
at: 14:00 room G O Jones 610  abstract: Understanding most basic thermodynamic properties of liquids such as energy and heat capacity turned out to be a longstanding problem in physics [1]. Landau&Lifshitz textbook states that no general formulas can be derived for liquid thermodynamic functions because the interactions are both strong and systemspecific. Phrased differently, liquids have no small parameter. Recent results have opened a new way to understand liquid thermodynamics on the basis of collective modes (phonons) as is done in the solid state theory. There are important differences between phonons in solids and liquids, and we have recently started to understand and quantify this difference. One striking difference is the emergence of a gap in the liquid phonon spectrum in the reciprocal space [2]. This brings an interesting question of what kind of field theory describes this gap. We recently proposed a twofield Lagrangian which accounts for dissipation and predicts the gap in momentum space [3]. The dissipative and mass terms compete by promoting gaps in kspace and energy, respectively (when bare mass is close to the field hopping frequency, both gaps close and the dissipative term annihilates the bare mass.) I will also discuss the recent attempt to canonically quantize this theory where I attempted to describe quantum dissipation which has been of interest recently. The Hamiltonian is quantized in terms of particles and antiparticles as in the complex scalar field theory and has the energy spectrum with the gap in momentum space. Finally, I will discuss the emergence of ultraviolet and infrared cutoffs in this theory due to dissipation. [1] K. Trachenko and V. V. Brazhkin, Collective modes and thermodynamics of the liquid state, Reports on Progress in Physics 79, 016502 (2016). [2] C. Yang, M. T. Dove, V. V. Brazhkin and K. Trachenko, Physical Review Letters 118, 215502 (2017). [3] K. Trachenko, Physical Review E 96, 062134 (2017). 
Regular Seminar Paul Fendley (Oxford)
at: 14:00 room G O Jones 610  abstract: I give an overview of work with Aasen and Mong on topological defects in twodimensional classical lattice models, quantum spin chains and tensor networks. The partition function in the presence of a topological defect is invariant under any local deformation of the defect. By using results from fusion categories, we construct topological defects in a wide class of lattice models, and show how to use them to derive exact properties of field theories by explicit lattice calculations. In the Ising model, the fusion of duality defects allows KramersWannier duality to be enacted on the torus and higher genus surfaces easily, implementing modular invariance directly on the lattice. In other models, the construction leads to generalised dualities previously unknown. A consequence is an explicit definition of twisted boundary conditions that yield the precise shift in momentum quantization and for critical theories, the spin of the associated conformal field. Other universal quantities we compute exactly on the lattice are the ratios of gfactors for conformal boundary conditions 
Regular Seminar Joseph Farrow (Durham U.)
at: 14:00 room G O Jones 610  abstract: I will introduce the framework of 4D scattering equations for calculating tree level super amplitudes in a variety of different theories, including Einstein supergravity and super YangMills theory. I will discuss my work on numerical solutions to these equations by Monte Carlo methods, and work with Arthur Lipstein on calculating N=4 conformal supergravity amplitudes in this framework. 
Regular Seminar Luis Fernando Alday (Oxford)
at: 14:00 room G O Jones 610  abstract:

Triangular Seminar Christopher Herzog (KCL)
at: 15:00 room Fogg Lecture Theatre  abstract: The infrared fixed point of graphene under the renormalization group flow is a relatively under studied yet important example of a boundary conformal field theory with a number of remarkable properties. It has a close relationship with three dimensional QED. It maps to itself under electricmagnetic duality. Moreover, it along with its supersymmetric cousins all possess an exactly marginal coupling  the charge of the electron  which allows for straightforward perturbative calculations in the weak coupling limit. I will review past work on this model and also discuss my own contributions, which focus on understanding the boundary contributions to the anomalous trace of the stress tensor and their role in helping to understand the structure of boundary conformal field theory. 
Triangular Seminar Diego Hofman (Amsterdam)
at: 16:30 room Fogg Lecture Theatre  abstract: Given two copies of any quantum mechanical system, one may want to prepare them in the thermofield double state for the purpose of studying thermal physics or black holes. However, the thermofield double is a unique entangled pure state and may be difficult to prepare. We propose a local interacting Hamiltonian for the combined system whose ground state is approximately the thermofield double. The energy gap for this Hamiltonian is of order the temperature. Our construction works for any quantum system satisfying the Eigenvalue Thermalization Hypothesis. 
Regular Seminar Bernardo Zan (EPFL Lausanne)
at: 14:00 room G O Jones 610  abstract: I will discuss walking behavior in gauge theories and weakly first order phase transition in statistical models. Despite being phenomena appearing in very different physical systems, they both show a region of approximate scale invariance. They can be understood as a RG flow passing between two fixed points living at complex couplings, which we call complex CFTs. By using conformal perturbation theory, knowing the conformal data of the complex CFTs allows us to make predictions on the observables of the walking theory. As an example, I will discuss the two dimensional Qstate Potts model with Q>4. 
Regular Seminar Monica Kang (Harvard)
at: 14:00 room G O Jones 610  abstract: Quantum error correction provides a convenient setup where bulk operators are defined only on a code subspace of the physical Hilbert space of the conformal field theory. I will first reformulate entanglement wedge reconstruction in the language of operatoralgebra quantum error correction with infinitedimensional physical and code Hilbert spaces. I will streamline my proof that for infinitedimensional Hilbert spaces, the entanglement wedge reconstruction is identical to the equivalence of the boundary and bulk relative entropies. I will discuss its implications for holographic theories with the ReehSchlieder theorem. 
Regular Seminar Carlo Meneghelli (Oxford)
at: 14:00 room G O Jones 610  abstract: To any fourdimensional N=2 superconformal field theory (SCFT) one can canonically associate a twodimensional vertex operator algebra (VOA). This provides a powerful framework for the analysis of SCFTs and leads to surprising predictions for a large new class of VOAs. In this talk I will present remarkable free field realizations of the relevant VOAs which mirror the effective field theory description of the corresponding four dimensional theory on the Higgs branch of its moduli space of vacua. 
Regular Seminar Sameer Murthy (KCL)
at: 14:00 room G O Jones 610  abstract: Supersymmetric localization is a powerful technique to evaluate a class of functional integrals in supersymmetric field theories. It reduces the functional integral over field space to ordinary integrals over the space of solutions of the offshell BPS equations. The application of this technique to supergravity suffers from some problems, both conceptual and practical. I will discuss one of the main conceptual problems, namely how to construct the fermionic symmetry with which to localize. I will show how a deformation of the BRST technique allows us to do this. As an application I will then sketch a computation of the oneloop determinant of the supergraviton that enters the localization formula for BPS black hole entropy. 
Regular Seminar Anastasios Petkou (Aristotle University of Thessaloniki)
at: 14:00 room G O Jones 610  abstract: Even if one knows everything for a conformal field theory on the infinite plane, new data are required to place the same theory in finite geometries. This is a physically relevant question for finitetemperature/finitesize critical systems. I will show in this talk how to apply an OPE inversion formula to thermal twopoint functions of bosonic and fermionic CFTs in general odd dimensions. This allows us to analyze in detail the operator spectrum of these theories. The main result is that nontrivial thermal CFTs arise when the thermal mass satisfies an algebraic transcendental equation that ensures the absence of an infinite set of operators from the spectrum. The solutions of these gap equations for general odd dimensions are in general complex numbers and follow a particular pattern. I will argue that this pattern unveils the largeN vacuum structure of the corresponding theories at zero temperature. 
Regular Seminar Alexander Tumanov (Tel Aviv U.)
at: 11:30 room G O Jones 610  abstract: Higher order corrections in the 1/N expansion to scattering amplitudes come from the diagrams with higher genus. One way to address these nontrivial topologies is to view them as planar objects glued into nonplanar configurations. They can then be "cut" across all the cycles of the corresponding Riemann surface, fixing the momentum flowing in each cycle. This procedure results in a planar object that belongs to a representation of the modular group of the Riemann surface in question. Various techniques developed for the planar amplitudes can be generalized to these cut nonplanar ones. We will investigate the scattering amplitude — Wilson loop duality, specifically focusing on the case of the first nonplanar correction, 1/N double trace amplitude, which has the topology of a cylinder. It’s dual space interpretation is a correlator of two infinite Wilson lines subject to a periodicity constraint. We will confirm this duality by a weak coupling perturbative calculation and a strong coupling string worldsheet one. This will allow us to construct the nonplanar loop integrands and the BCFW recursion relation they satisfy, as well as to find an interpretation of the dual conformal symmetry in the nonplanar sector, which was previously thought to be broken by 1/N corrections. Lastly, we will discuss this result in the framework of the Wilson Loop OPE approach, which allows one to compute expectation values of Wilson loops at any value of the coupling in the form of an expansion around the collinear limit. We claim that this approach can be directly applied to cut nonplanar scattering amplitudes, as well as the N=4 SYM form factors, whose dual space interpretation is remarkably similar to the one of the 1/N amplitude correction. 
Triangular Seminar Dionysios Anninos (Amsterdam)
at: 15:00 room Fogg Lecture Theatre  abstract: We overview some aspects of asymptotically de Sitter spacetimes at the classical and quantum level. We discuss some features of the late time de Sitter wavefunction. We briefly touch upon some properties of the relation between de Sitter space and Euclidean conformal theories, broadly referred to as the dS/CFT correspondence. Finally, time permitting, we will discuss some similarities and differences between the cosmological dS horizon and a more standard black hole horizon. 
Regular Seminar Costantin Bachas (ENS Paris)
at: 14:00 room G O Jones 610  abstract: I will first review the AdS4/SCFT3 correspondence with N=4 supersymmetry. I will then focus on two special aspects which are important in exploring the string landscape: (1) The existence of N=2 moduli and their fate in gauged supergravity; (2) Special degeneration limits for which the lowenergy limit is a theory of bigravity or massive gravity. 
Regular Seminar Diego RodriguezGomez (Oviedo U.)
at: 14:00 room G O Jones 610  abstract: Disconnected gauge groups have been, at least comparatively, very poorly studied. Yet they may hide very interesting Physics. Recently, a class of gauge theories based on a particular type of disconnected gauge groups, namely principal extensions, has been introduced. Interestingly, such theories naturally implement the gauging of charge conjugation. In this talk, we will describe such construction and study aspects of its Physics. A particularly spectacular byproduct of the construction is that these theories have nonfreely generated Coulomb branches, thus providing the first counterexample of the long standing standard lore that Coulomb branch are all freely generated. 
Regular Seminar Karthik Inbasekar (Tel Aviv U.)
at: 14:00 room G O Jones 610  abstract: ChernSimons theories coupled to fundamental matter have a wide variety of applications ranging from Quantum Hall effect to Quantum gravity via AdS/CFT. These theories enjoy a strong weak duality that has been tested to a very good accuracy via large N computations, such as thermal partition functions, and S matrices. Supersymmetric ChernSimons theories are equally interesting since they have a self duality and relate to nonsupersymmetric theories via RG flows. In the N=2,3 supersymmetric ChernSimons matter theories, the four point amplitude computed to all orders in the 't Hooft coupling is not renormalised! It is a unique situation in a quantum field theory that the scattering amplitude doesn't receive loop corrections. This indicates the presence of powerful symmetry structures within the theory. This also suggests that higher point amplitudes may be easier to compute using four point amplitudes as building blocks. These higher point amplitudes not only serve as a testing tool for duality but also a probe into the symmetry structure of the theory. As a first step towards this goal, we begin by computing arbitrary n point tree level amplitudes in the N=2 theory via BCFW recursion relations. We then show that the four point tree level amplitude enjoys a dual superconformal symmetry. Since the all loop four point amplitude is tree level exact, it follows that the dual superconformal symmetry is exact to all loops. This is in contrast to highly supersymmetric examples such as N=4 SYM and N=6 ABJM, where the dual superconformal symmetry is in general anomalous. Furthermore, we show that the superconformal and dual superconformal symmetries generate an infinite dimensional Yangian symmetry for the four point amplitude. If these symmetries persist to higher point amplitudes, this suggests that the N=2 superconformal ChernSimons matter theory may be integrable. 
Regular Seminar Gabriel Wong (Fudan U)
at: 14:00 room G O Jones 610  abstract: What is the meaning of entanglement in a theory of extended objects such as strings? To address this question we consider the spatial entanglement between two intervals in the GrossTaylor model, the string theory dual to twodimensional YangMills theory at large N. The string diagrams that contribute to the entanglement entropy describe open strings with endpoints anchored to the entangling surface, as first argued by Susskind. We develop a canonical theory of these open strings, and describe how closed strings are divided into open strings at the level of the Hilbert space. We derive the Modular hamiltonian for the HartleHawking state and show that the corresponding reduced density matrix describes a thermal ensemble of open strings ending on an object at the entangling surface that we call an Ebrane. 
Regular Seminar Ronnie Rodgers (Southampton U.)
at: 14:00 room G O Jones 610  abstract: Mtheory is a candidate for a theory of quantum gravity. Its fundamental objects are called M2branes and M5branes. The lowenergy theory describing coincident M5branes is poorly understood in many respects, with holography providing one of the most useful tools to further that understanding. It is known that the theory should possess solitonic solutions called "selfdual strings". An important quantity characterising these strings is their central charge, which among other things counts the massless degrees of freedom on the string. I will describe configurations of Mbranes dual to the insertion of infinite tension selfdual strings into the M5brane theory, and how calculation of holographic entanglement entropy in such setups yields the central charge of the selfdual string. 
Regular Seminar JeongHyuck Park (Sogang University)
at: 15:30 room 410  abstract: String theory predicts its own gravity rather than GR. In General Relativity the metric is the only geometric and gravitational field, whereas in string theory the closedstring massless sector comprises a skewsymmetric Bfield and the string dilaton in addition to the metric. Furthermore, these three fields transform into each other under Tduality. This hints at a natural augmentation of GR: upon treating the whole closed string massless sector as stringy graviton fields, Double Field Theory may evolve into `Stringy Gravity'. Equipped with an O(D,D) covariant differential geometry beyond Riemann, we spell out the definitions of the stringy Einstein curvature tensor and the stringy EnergyMomentum tensor. Equating them, all the equations of motion of the closed string massless sector are unified into a single expression which we dub the Einstein Double Field Equations. 
Regular Seminar David Berenstein (UC Santa Barbara)
at: 14:00 room G O Jones 610  abstract:
