## 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)

### 29.09.2016 (Thursday)

#### On the null origin of the ambitwistor string

Regular Seminar Eduardo Casali (Oxford U.)

 at: 14:00 QMWroom G.O. Jones 610 abstract: The Cachazo-He-Yuan (CHY) formulas are a remarkable representation of tree-level massless scattering amplitudes. Similarly to the Twistor String formulas, the CHY formula presents amplitudes as an integrals over the moduli space of Riemann surfaces constrained to the solutions of a set of algebraic equations called the scattering equations. But contrary to the Twistor String formulas, they can be written in for any dimension and for a variety of massless theories. Behind the original CHY formula and the scattering equations lies a 2D CFT called the Ambitwistor String, much like the original Twistor String, this is a chiral CFT in which correlators of vertex operators reproduce the CHY formulas and give a geometric interpretation of the scattering equations. The Ambitwistor string possesses a few peculiar characteristics when viewed as a string theory, its low energy efective action is the same as Type II closed strings but the appearance of the scattering equations suggests a high-energy limit has been taken a la Gross and Mende. Besides, its genus one correlation functions are modular invariant but UV divergent since they correspond to 10D SUGRA amplitudes. In this talk I'll talk about a program started with P. Tourkine in which the Ambitwistor String (and other Twistor Strings) are treated as coming from the tensionless limit of classcial string theories. These are know as null strings and have a long history in the literature. I'll review the null string and its supersymmetric extensions and show how the Ambitwistor String can be obtained from a particular gauge fixing of the null string. In doing so, I'll address the issue of possible inequivalent quantizations of the null string and compare it to the case of the usual string and shed a light its relation to the Ambitwistor String.

### 15.09.2016 (Thursday)

#### Holography inspired stringy hadrons

Regular Seminar Cobi Sonnenschein (Tel Aviv University)

 at: 14:00 QMWroom G.O. Jones 610 abstract:

### 23.06.2016 (Thursday)

#### Bremsstrahlung function, leading Luscher correction at weak coupling and localization

Regular Seminar Michelangelo Preti (Parma U.)

 at: 14:00 QMWroom G.O. Jones 610 abstract: We discuss the near BPS expansion of the generalized cusp anomalous dimension with L units of R-charge. Integrability provides an exact solution, obtained by solving a general TBA equation in the appropriate limit: we propose here an alternative method based on supersymmetric localization. The basic idea is to relate the computation to the vacuum expectation value of certain 1/8 BPS Wilson loops with local operator insertions along the contour. These observables localize on a two-dimensional gauge theory on S^2, opening the possibility of exact calculations. As a test of our proposal, we reproduce the leading Luscher correction at weak coupling to the generalized cusp anomalous dimension. This result is also checked against a genuine Feynman diagram approach in N=4 Super Yang-Mills theory.

### 16.06.2016 (Thursday)

#### Surface defects as vortex strings in class S_k

Regular Seminar Hironori Mori (Osaka University)

 at: 14:00 QMWroom G.O. Jones 610 abstract: We investigate the aspects of surface defects in a new class of 4d N=1 superconformal quiver theories named class S_k. As the first step, we focus on the construction of the surface defects in IR under the situation where the UV theories of class S_k are higgsed by giving the vevs to some fields and try to specify them as 2d N=(0,2) vortex string theories by computing its elliptic genera encoded in the IR description of the superconformal indices of class S_k. This picture is consistent with type IIA brane construction of the vortex strings. Another way to argue the surface defects is to see their actions on the superconformal indices as difference operators, and we would like to discuss whether such difference operators form the algebras labelled by the representations of SU(N) flavor symmetries.

### 02.06.2016 (Thursday)

#### Supertanslation symmetry at the black hole horizon

Regular Seminar Gaston Giribet (University of Buenos Aires)

 at: 14:00 QMWroom G.O. Jones 610 abstract:

### 26.05.2016 (Thursday)

#### Super String Field Theory Revisited

Regular Seminar Ivo Sachs (LMU)

 at: 14:00 QMWroom G.O. Jones 610 abstract: I first describe the remarkably simple algebraic structure underlying covariant string field theory. No knowledge of string field theory and only very basic concepts of string theory are required for this. I then use this structure to construct the superstring field theory action recursively and discuss its relation to the decomposition of (super) moduli spaces. I will focus mostly on open string theory but will comment on the generalisation to closed string.

### 20.05.2016 (Friday)

#### Graduate Mini-Course: Sectors of Supersymmetric Field Theories

Informal Seminar Matthew Buican (QMUL)

 at: 10:30 QMWroom GOJ 610 abstract: Lecture 3: "Toward a Synthesis of Chiral Rings and Chiral Algebras." I will aim to discuss some recent work that seeks to relate the objects introduced in the first two lectures. Given enough time, we may also discuss generalizations of these ideas.

### 19.05.2016 (Thursday)

#### d-Dimensional Generalised Unitarity and Colour-Kinematics duality

Regular Seminar William Javier Torres Bobadilla (Padua U.)

 at: 14:00 QMWroom G.O. Jones 610 abstract: In this talk I plan to introduce the Four-Dimensional-Formulation (FDF) regularisation scheme proposed in arXiv:1404.4783 [hep-ph], which allows a four-dimensional representation of the d-dimensional particles propagating in the loop. Within FDF, I present the computation of one-loop QCD corrections of the processes gg>>gggg and gg>>Hggg (in the heavy top limit). On the other hand, I show the extension of Colour-Kinematics relations in d-dimensions and their application to compute efficiently one-loop amplitudes.

### 18.05.2016 (Wednesday)

#### Graduate Mini-Course: Sectors of Supersymmetric Field Theories

Informal Seminar Matthew Buican (QMUL)

 at: 10:30 QMWroom GOJ 610 abstract: Lecture 2: "Chiral Algebras and Higher-Dimensional Theories." I will review briefly review the construction of chiral algebras and then focus on their relationship with a particular sub-sector of operators in higher-dimensional theories. I will again focus mostly on 4D N=2 theories.

### 16.05.2016 (Monday)

#### Graduate Mini-Course: Sectors of Supersymmetric Field Theories

Informal Seminar Matthew Buican (QMUL)

 at: 10:30 QMWroom GOJ 610 abstract: Lecture 1: "Chiral Rings, Moduli Spaces, and Conformal Manifolds." In this lecture I will review basic aspects of chiral operators, with a special focus on 4D theories with 8 Poincare supercharges (i.e., N=2 SUSY). Using these operators, I will discuss basic aspects of moduli spaces and conformal manifolds.

### 12.05.2016 (Thursday)

#### One-point Functions of AdS/dCFT from Matrix Product States

Regular Seminar Charlotte Kristjansen (NBI)

 at: 14:00 QMWroom G.O. Jones 610 abstract: One-point functions of certain non-protected scalar operators in the defect CFT dual to the D3-D5 probe brane system with k units of world volume flux can be expressed as overlaps between Bethe eigenstates of the Heisenberg spin chain and a matrix product state. We present a closed expression of determinant form for these one-point functions, valid for any value of k. The determinant formula factorizes into the k=2 result times a k-dependent prefactor. Making use of the transfer matrix of the Heisenberg spin chain we recursively relate the matrix product state for higher even and odd k to the matrix product state for k=2 and k=3 respectively. We furthermore find evidence that the matrix product states for k=2 and k=3 are related via a ratio of Baxter's Q-operators. The general k formula has an interesting thermodynamical limit involving a non-trivial scaling of k, which indicates that the match between string and field theory one-point functions found for chiral primaries might be tested for non-protected operators as well. We revisit the string computation for chiral primaries and discuss how it can be extended to non-protected operators.

### 05.05.2016 (Thursday)

#### Quantum Linguistics?

 at: 14:00 QMWroom G.O. Jones 610 abstract: Mathematical models of natural language can be organised into logical and statistical. The former are based on grammatical structures of phrases and sentences and the latter on distributions of words in corpora of text. In joint work with Clark (Cambridge) and Coecke (Oxford), we developed a unifying framework where the distributions of words are composed to form distributions for phrases and sentences. This expanded the application domains of the statistical models -- e.g. automatic reasoning about similarity -- from words to phrases and sentences. On the theoretical side, our model extends the word-based setting from vectors to tensors. Tensors are main players in the mathematical models of quantum mechanics. In this talk, I will review the theory and applications of our model in simple terms and through examples. I will briefly explain how `entanglement', a concept arising from tensors in quantum mechanics, manifests itself and is used as a resource in the linguistic applications. I will also explain how the reasoning toolkit used in this model is the same as that of Abramsky and Coecke in their categorical Quantum Mechanics model.

### 28.04.2016 (Thursday)

#### Black Hole Collisions in Asymptotically anti-de Sitter Spacetimes

Regular Seminar Hans Bantilan (QMUL)

 at: 14:00 QMWroom G.O. Jones 610 abstract: The collision of black holes is a classic problem in the strong-field regime of general relativity, with no known closed-form solution. When exact solutions are not known, or perturbative expansions about known solutions are inadequate to capture the non-linear dynamics, the numerical solution of the Einstein field equations is required. The main purpose of this talk is to describe, in detail, the necessary ingredients for achieving stable Cauchy evolution of black hole collisions in asymptotically anti-de Sitter (AdS) spacetimes. I will begin by motivating this program in terms of the heavy-ion physics it is intended to clarify. I will then give an overview of anti-de Sitter space, the mapping to its dual boundary conformal field theory, and the method we use to numerically solve the fully non-linear Einstein field equations with AdS boundary conditions. As a concrete example of these ideas, I will describe simulations of stable AdS black hole mergers in 5 dimensions.

### 21.04.2016 (Thursday)

#### Tachyonic Antibranes and the deSitter and Fuzzball Landscapes

Regular Seminar Iosif Bena (Saclay)

 at: 14:00 QMWroom G.O. Jones 610 abstract: Antibranes in backgrounds that have charge dissolved in fluxes are a key ingredient in constructing a landscape (Multiverse) of deSitter vacua in String Theory, and also of constructing microstate solutions corresponding to non-supersymmetric near-extremal black holes. There are several regimes of parameters in which one can study the physics of these antibranes, and I will show that in the regime of parameters where their gravitational backreaction is important, antibranes have a naked singularity that cannot be resolved either by brane polarization or by cloaking with a black hole horizon, and that signals a tachyonic instability. I will also present recent evidence that the theory on the wordvolume of anti-D3 branes is finite to all loops. I will conclude by discussing the implications of these results for the Multiverse paradigm and for the Fuzzball proposal.

### 14.04.2016 (Thursday)

#### Constraints on the CFT three point functions

Regular Seminar Manuela Kulaxizi (Trinity College Dublen)

 at: 14:00 QMWroom G.O. Jones 610 abstract: We discuss the energy flux constraints for conserved and non-conserved operators in an arbitrary higher dimensional CFT. We then consider a deep inelastic scattering thought experiment and show how to derive these and other bounds on the OPE coefficients of various operators.

### 07.04.2016 (Thursday)

#### Scrambling without chaos

Regular Seminar Alvaro Veliz Osorio (QMUL)

 at: 14:00 QMWroom G.O. Jones 610 abstract: We investigate measures of chaos and entanglement scrambling in rational conformal field theories in 1+1 dimensions. First, we derive a formula for the late time value of the out-of-time-order correlators for these class of theories. Our universal result can be expressed as a particular combination of the modular S-matrix elements known as anyon monodromy scalar. Next, in the explicit setup of a SU(N)k WZW model, we compare the late time behaviour of the out-of-time correlators and the purity. Interestingly, in the large-c limit, the purity grows logarithmically but the out-of-time-order correlators remain constant. Therefore, we find that some systems may display entanglement scrambling in the absence of chaos.

### 31.03.2016 (Thursday)

#### Bootstrapping N=2 SCFTs

Regular Seminar Madalena Lemos (DESY Hamburg)

 at: 14:00 QMWroom G.O. Jones 610 abstract: In this talk we will discuss the bootstrap program applied to four-dimensional N=2 superconformal field theories, with focus on analytical results. After a brief review of the protected subsector captured by a two-dimensional chiral algebra, we will show how analytic bounds on anomaly coefficients are obtained and constrain the space of allowed SCFTs. Finally we will comment the implications for the numerical bootstrap program.

### 10.03.2016 (Thursday)

#### 3d N=2 dualities with monopoles

Regular Seminar Sara Pasquetti (Surrey U.)

 at: 14:00 QMWroom G.O. Jones 610 abstract: I will present several new 3d N=2 dualities with super-potentials involving monopole operators. Some of the theories that I will discuss describe systems of D3 branes ending on pq-webs. In these cases 3d mirror symmetry is a consequence of S-duality.

### 02.03.2016 (Wednesday)

#### Probing N=2 SUSY gauge theories with surface operators

Triangular Seminar Joerg Teschner (DESY)

 at: 15:00 QMWroom Maths Lecture Theatre abstract:

### 02.03.2016 (Wednesday)

#### Soft Hair on Black Holes

Triangular Seminar Malcolm Perry (DAMTP)

 at: 16:30 QMWroom Maths Lecture Theatre abstract: