Directions

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 15-20 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.

Seminars at Queen Mary University of London

Found at least 20 result(s)

23.05.2019 (Thursday)

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Regular Seminar Michele Levi (IPhT Saclay)

at:
14:00 QMW
room G O Jones 610
abstract:

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20.05.2019 (Monday)

All N=4 conformal supergravities

Regular Seminar Franz Ciceri (AEI Potsdam)

at:
15:00 QMW
room G O Jones 610
abstract:

Supersymmetric extensions of conformal gravity have been known for a long time. In four dimensions, N=4 conformal supergravity is the maximally supersymmetric theory of this type. Although its field representation and the non-linear transformations rules were derived more than 30 years ago, no invariant action had been constructed so far. We present the most general class of actions which turns out to be characterised by a holomorphic function. This deviates from the non-maximally supersymmetric cases where the action is unique. Meanwhile, elaborate loop computations have indicated that N=4 Poincare supergravity diverges at four loops, and the divergence is believed to be related to the presence of a potential one-loop anomaly in the duality symmetry of the theory. We argue that one of the constructed conformal actions, after gauge fixing the conformal symmetries and carefully eliminating auxiliary fields, can be used as a finite supersymmetric counterterm that cancels the anomalous contribution of the one-loop graphs in the Poincare theory.

16.05.2019 (Thursday)

On Integrable Subsectors of AdS/CFT and LLM geometries

Regular Seminar Jaco van Zyl (Witwatersrand U.)

at:
14:00 QMW
room G O Jones 610
abstract:

The 1/2 BPS and regular LLM geometries are formed from the backreaction of a large number of D-branes on AdS_5 x S^5. The dual N=4 SYM operator to this configuration, and excitations thereof, thus lie outside of the planar limit of the theory. Explicitly the operators dual to these geometries are Schur polynomials labelled by a Young diagram with O(N^2) boxes and excitations of this configuration are restricted Schur polynomials obtained by adding boxes (and restriction labels) to this diagram. A special class of these geometries are labelled by Young diagrams with O(1) well separated corners. In the large N limit excitations localised at any one of these corners only mix with each other which is a major simplification. A recent proposal has argued that the large N dynamics of these operators is isomorphic to that of planar N=4 SYM and thus represents an integrable subsector of N=4 SYM. In this talk this proposal is reviewed and aspects of the weak and strong coupling evidence presented.

13.05.2019 (Monday)

Quo Vadis: colliders?

Regular Seminar Rohini Godbole (Indian Institute of Science)

at:
15:00 QMW
room G O Jones 610
abstract:

After a summary of current status of experimental results in particle physics, including the presentation of what I call the LHC paradox, I will discuss briefly how colliders were indispensible in arriving at this point of the journey. After this I would discuss what the next steps are: as to where do we go from here in the story of collider physics. If time is left, I will discuss some of the issues that the future colliders can address , by taking examples from the known unknowns, viz. in the framework of particular BSM models and also the unknown unknowns viz the model independent approach.

09.05.2019 (Thursday)

Infrared enhancement of supersymmetry in four dimensions

Regular Seminar Simone Giacomelli (Oxford)

at:
14:00 QMW
room G O Jones 610
abstract:

In this seminar I will discuss a recently-found class of RG flows in four dimensions exhibiting enhancement of supersymmetry in the infrared, which provides a lagrangian description of several strongly-coupled N=2 SCFTs. The procedure involves starting from a N=2 SCFT, coupling a chiral multiplet in the adjoint representation of the global symmetry to the moment map of the SCFT and turning on a nilpotent expectation value for this chiral. We show that, combining considerations based on 't Hooft anomaly matching and basic results about the N=2 superconformal algebra, it is possible to understand in detail the mechanism underlying this phenomenon and formulate a simple criterion for supersymmetry enhancement.

25.04.2019 (Thursday)

Boundary renormalisation group interfaces

Regular Seminar Anatoly Konechny (Heriot-Watt University)

at:
14:00 QMW
room G.O. Jones 610
abstract:

Renormalisation group (RG) interfaces were introduced by I. Brunner and D. Roggenkamp in 2007. To construct such an interface consider perturbing a UV fixed point, described by a conformal field theory (CFT), by a relevant operator on a half space. Renormalising and letting the resulting QFT flow along the RG flow we obtain a conformal interface between the UV and IR fixed point CFTs. Although enjoying a full conformal symmetry this interface carries information about the RG flow it originated from. In this talk I will consider a rather special case of the RG interface between two boundary conditions of a 2D CFT which is obtained from a boundary RG flow interpolating between two conformal boundary conditions. This interface is zero-dimensional and is thus described by a local boundary-condition changing operator. I investigate its properties in concrete models and formulate a number of general conjectures that can help charting phase diagrams of boundary RG flows.

11.04.2019 (Thursday)

Supersymmetric space-dependent deformations of ABJM

Regular Seminar Matthew Roberts (Imperial)

at:
14:00 QMW
room G O Jones 610
abstract:

We construct new supersymmetric solutions of 11D supergravity, preserving 1/4 of the supersymmetry, that are dual to the ABJM Chern-Simons-matter theory deformed by mass terms which depend on one spatial direction. The BPS equations boil down to solving the Helmholtz equation on the complex plane giving rise to rich classes of new solutions. In particular, the construction gives rise to infinite classes of new supersymmetric “boomerang” RG flows, as well as generalising other previously known solutions.

28.03.2019 (Thursday)

Partial deconfinement and holographic black holes

Regular Seminar David Berenstein (UC Santa Barbara)

at:
14:00 QMW
room G O Jones 610
abstract:

I will describe simple models of holography that can display some of the thermodynamics associated to small black holes. These phenomena include negative specific heat and localization on additional dimensions of the geometry. I will also explain how the dynamics of these states should naturally be thought of as partial deconfinement on a submatrix set of degrees of freedom of the model.

21.03.2019 (Thursday)

From Soft Corrections to Ultra-Planckian Scattering and back

Regular Seminar Massimo Bianchi (Roma Tor Vergata)

at:
14:00 QMW
room G O Jones 610
abstract:

Ultra-planckian collisions represent a fertile arena where to test quantum theories of gravity such as string theory. Glimpses of black hole formation and evaporation can be taken. For suitably defined infrared-safe observables, we show that the `classicalization' approach to high-multiplicity processes agrees with the ACV approach based on the resummation of ladder diagrams. Since a significant fraction of energy is lost in gravitational bremsstrahlung, we re-derived the zero-frequency limit (ZFL) of the GW flux using soft graviton theorems at leading order and compute the corrections at sub- and sub-sub-leading order. For massless two-particle elastic collisions the former is shown to vanish, while the latter takes an explicit expression which is checked against a simple tree-level process.However, if the tree-level form of the soft theorems is used at sub-sub-leading order even when the elastic amplitude needs resummation, an unphysical IR singularity occurs due to the infinite Coulomb phase. We briefly discuss a recent proposal as how to deal with these divergences and find agreement with the eikonal approach.

18.03.2019 (Monday)

Moduli spaces of 4-dimensional N=3 superconformal field theories

Exceptional Seminar Philip Argyres (University of Cincinnati)

at:
11:00 QMW
room G.O. Jones 610
abstract:

28.02.2019 (Thursday)

Asymptotic charges in gravity

Regular Seminar Mahdi Godazgar (QMUL)

at:
14:00 QMW
room G O Jones 610
abstract:

I will give an overview of my recent research on the definition of asymptotic charges in asymptotically flat spacetimes, including the definition of subleading BMS charges and the relation to the conserved Newman-Penrose charges at null infinity.

22.02.2019 (Friday)

Hecke relations and Galois symmetries in Rational Conformal Field Theories and Modular Tensor Categories

Exceptional Seminar Jeff Harvey (The University of Chicago)

at:
11:30 QMW
room 610
abstract:

I will discuss some old and new relations between the characters, modular data and braiding and fusing matrices of rational conformal field theories and their associated modular tensor categories. These relations involve concepts from number theory which I will explain in the talk.

21.02.2019 (Thursday)

Reflection and transmission coefficients for conformal interfaces.

Regular Seminar Marco Meineri (EPFL, Lausanne)

at:
14:00 QMW
room G O Jones 610
abstract:

We probe a generic two dimensional conformal interface via a collider experiment. We measure the energy and charges which are reflected and transmitted through the interface. We find that the average transmitted energy is independent of the way the state is constructed and determined by the central charge and a single piece of CFT data. We comment on the universality of the result and discuss some examples.

14.02.2019 (Thursday)

How logarithms are born

Regular Seminar Melissa van Beekveld (IMAPP Njimegen)

at:
14:00 QMW
room G O Jones 610
abstract:

I will show how large logarithms arise in a perturbative calculation and how resummation solves the issue of having these large logarithms. If there is some time left, I want to show some recent progress that we have made on pinning down the origin of the next-to-leading class of logarithms.

31.01.2019 (Thursday)

Field theory of gapped momentum states

Regular Seminar Kostya Trachenko (QMUL)

at:
14:00 QMW
room G O Jones 610
abstract:

Understanding most basic thermodynamic properties of liquids such as energy and heat capacity turned out to be a long-standing 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 system-specific. 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 two-field Lagrangian which accounts for dissipation and predicts the gap in momentum space [3]. The dissipative and mass terms compete by promoting gaps in k-space 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).

24.01.2019 (Thursday)

The Uses of Lattice Topological Defects

Regular Seminar Paul Fendley (Oxford)

at:
14:00 QMW
room G O Jones 610
abstract:

I give an overview of work with Aasen and Mong on topological defects in two-dimensional 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 Kramers-Wannier 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 g-factors for conformal boundary conditions

17.01.2019 (Thursday)

4D scattering equations, Monte Carlo methods, and conformal supergravity

Regular Seminar Joseph Farrow (Durham U.)

at:
14:00 QMW
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 Yang-Mills 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.

13.12.2018 (Thursday)

Genus-One String Amplitudes from Conformal Field Theory

Regular Seminar Luis Fernando Alday (Oxford)

at:
14:00 QMW
room G O Jones 610
abstract:

05.12.2018 (Wednesday)

Graphene and Boundary Conformal Field Theory

Triangular Seminar Christopher Herzog (KCL)

at:
15:00 QMW
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 electric-magnetic 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.

05.12.2018 (Wednesday)

How to Build the Thermofield Double State

Triangular Seminar Diego Hofman (Amsterdam)

at:
16:30 QMW
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.