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.

`Found at least 20 result(s)`

Informal Seminar Ricardo Monteiro (QMUL)

at:10:30
room GO Jones 610 | abstract: I will give an introduction to current topics in the study of scattering amplitudes of gauge theory and gravity. There will be four two-hour lectures, and the plan is as follows. Lecture 1 will review basic modern techniques for scattering amplitudes, including recursion relations. Lecture 2 will present an overview of the relations describing gravity as a double copy of gauge theory, both for scattering amplitudes and for solutions to the equations of motion. Lecture 3 will introduce the formalism of the scattering equations, leading to the CHY formulas for amplitudes in theories of massless particles. Lecture 4 will present new developments in computing field-theory amplitudes from string-theory-inspired techniques, via a new type of worldsheet model known as ambitwistor string. This leads to an extension of the scattering equations to loop level. |

Informal Seminar Ricardo Monteiro (QMUL)

at:10:00
room GO Jones 610 | abstract: I will give an introduction to current topics in the study of scattering amplitudes of gauge theory and gravity. There will be four two-hour lectures, and the plan is as follows. Lecture 1 will review basic modern techniques for scattering amplitudes, including recursion relations. Lecture 2 will present an overview of the relations describing gravity as a double copy of gauge theory, both for scattering amplitudes and for solutions to the equations of motion. Lecture 3 will introduce the formalism of the scattering equations, leading to the CHY formulas for amplitudes in theories of massless particles. Lecture 4 will present new developments in computing field-theory amplitudes from string-theory-inspired techniques, via a new type of worldsheet model known as ambitwistor string. This leads to an extension of the scattering equations to loop level. |

Informal Seminar Ricardo Monteiro (QMUL)

at:10:00
room GO Jones 610 | abstract: I will give an introduction to current topics in the study of scattering amplitudes of gauge theory and gravity. There will be four two-hour lectures, and the plan is as follows: Lecture 1 will review basic modern techniques for scattering amplitudes, including recursion relations. Lecture 2 will present an overview of the relations describing gravity as a double copy of gauge theory, both for scattering amplitudes and for solutions to the equations of motion. Lecture 3 will introduce the formalism of the scattering equations, leading to the CHY formulas for amplitudes in theories of massless particles. Lecture 4 will present new developments in computing field-theory amplitudes from string-theory-inspired techniques, via a new type of worldsheet model known as ambitwistor string. This leads to an extension of the scattering equations to loop level. |

Exceptional Seminar Paolo Di Vecchia (NBI/Nordita)

at:12:00
room GO Jones LG7 | abstract: In this talk we will discuss how gauge invariance fixes the soft behavior of massless particles as photons, gluons, gravitons, dilatons and Kalb-Ramond field. We will then check these results in string theory and we will show that the subsubleading behavior for gravitons includes string corrections in the bosonic and heterotic strings, but not in superstring. They are consequence of the fact that the three-graviton amplitude has string corrections with respect to the field theoretical one. It turns out, instead, that the soft behavior of the dilaton has no string corrections and, in particular, involves the generators of dilatations and special conformal transformations. We then study the soft behavior of the Goldstone boson, called in the literature also dilaton, that one gets when one breaks spontaneously the conformal symmetry and we show that its soft behavior is very similar, but not identical, to that of the string dilaton. |

Regular Seminar Elli Pomoni (DESY)

at:14:00
room 610 | abstract: We will introduce a large class of N=1 superconformal theories Sk which is obtained from Gaiotto’s N=2 class S via orbifolding. We will study the Coulomb branch of the theories in the class by constructing and analyzing their spectral curves. Using our experience from the N=2 AGT correspondence we will search for a 2D/4D relations (AGTk) for the N=1 theories of class Sk. From the curves we will identify the 2D CFT symmetry algebra and its representations, namely the conformal blocks of the Virasoro/W-algebra, that underlie the 2D theory and reproduce the Seiberg-Witten curves of the N = 1 gauge theories. We find that the blocks corresponding to the SU(N) Sk gauge theories involve fields in certain non-unitary representations of the WkN algebra. These conformal blocks give a prediction for the instanton partition functions of the 4D N = 1 SCFTs of class Sk. |

Regular Seminar Tommi Tenkanen (QMUL)

at:14:00
room G.O. Jones 610 | abstract: The nature of the unknown non-baryonic energy density component whose abundance is known to exceed the amount of ordinary, visible matter by a factor of five, that of Dark Matter (DM), is one of the greatest open problems in cosmology. In this talk I will briefly review the evidence and searches for DM, present an overview of candidates including the standard WIMP paradigm, and discuss some recently proposed alternatives for WIMPs and how to test them. |

Regular Seminar Menika Sharma (Harish-Chandra)

at:14:00
room G.O. Jones 610 | abstract: String theory in the tensionless limit is expected to have a large gauge symmetry. By recasting string theory on the AdS background as a generalization of Vasiliev's theory of massless higher-spin fields, it has become possible to understand the nature of this symmetry. In this talk, I will first give an overview of three-dimensional Vasiliev theory and its dual CFT. I will then discuss the current understanding of the symmetry algebra of string theory as well as some open problems related to it. |

Regular Seminar Richard Szabo (Heriot Watt)

at:14:00
room G.O. Jones 610 | abstract: Recent advances in non-geometric string theory suggest that locally non-geometric flux compactifications can be understood in terms of nonassociative deformations of spacetime geometry. We will review some of these developments and how they shed light on properties of non-geometric strings, and explain some new results concerning how these structures lift to non-geometric M-theory |

Triangular Seminar Michael Green (DAMTP/QMUL)

at:15:00
room G.O. Jones Lecture Theatre | abstract: This talk will focus on some recent results concerning the low energy expansion of superstring scattering amplitudes. Whereas tree-level amplitudes generate a series of multiple zeta values (MZV) the genus-one amplitudes generate a series of elliptic generalisations (“modular graph functions”) that satisfy fascinating polynomial relations analogous to those satisfied by MZV’s. The latter part of the talk will briefly review how these features fit in with the non-perturbative structure of superstring amplitudes, studied some time ago. |

Triangular Seminar Niklas Beisert (ETH Zurich)

at:16:30
room G.O. Jones Lecture Theatre | abstract: This talk is about integrability of Planar N=4 super Yang-Mills theory. We present a concrete notion of the corresponding Yangian symmetry in this model, show that it holds true, and discuss the (perturbative) implications for correlation functions and Wilson loops. |

Regular Seminar Linus Wulff (Imperial)

at:14:00
room G.O. Jones 610 | abstract: It has been known since the 80's that the Green-Schwarz superstring possesses the fermionic kappa symmetry, required for the consistency of the formulation, if the target space is a solution of the supergravity equations of motion. However, contrary to the standard lore and previous claims in the literature, it was recently shown that the converse is not true. Kappa symmetry of the Green-Schwarz superstring implies only a weaker set of equations for the target space fields, which we refer to as generalized supergravity equations. I will describe these equations for the type II case and contrast them with the standard type II supergravity equations which arise as a special case. |

Regular Seminar Gabor Takacs (Budapest U.)

at:14:00
room G.O. Jones 610 | abstract: I present the results of a study of a (1 +1 )-dimensional version of the famous Nambu-Jona-Lasinio model of quantum chromodynamics both at zero and at finite baryon density. For zero chemical potential, we found the formation of fermionic (nucleons and Δ baryons) and bosonic (two-quark mesons, six-quark deuterons) excitations, and demonstrated the existence of a phase transition. For a finite baryon density the model has a rich phase diagram which includes phases with a density wave and superfluid quasi-long-range (QLR) order, as well as a phase of a baryon Tomonaga-Luttinger liquid (strange metal). Relevant publication: P. Azaria, R.M. Konik, Ph. Lecheminant, T. Pálmai, G. Takács and A.M. Tsvelik: Particle Formation and Ordering in Strongly Correlated Fermionic Systems: Solving a Model of Quantum Chromodynamics, Phys. Rev. D94 (2016) 045003, arXiv:1601.02979 [hep-th]. |

Regular Seminar Susha Parameswaran (University of Liverpool)

at:14:00
room G.O. Jones 610 | abstract: An early epoch of cosmic inflation, driven by a scalar field slowly rolling down a flat potential, provides an elegant solution to several cosmological puzzles. The notorious sensitivity of the slow roll potential to quantum gravity effects, presents both a challenge and opportunity for string theory to connect to observations. A very promising way to explain slow roll inflation is with an axionic inflaton field, whose flat potential is protected by a perturbative shift symmetry. However, the canonical models of axion inflation - "Natural Inflation" and "Axion Monodromy" - are now both in tension with observations and difficult to embed in a UV complete theory like string theory. I will discuss these challenges, and also a way to overcome them, with an inflationary mechanism - beyond slow roll - that is well-motivated from string theory and consistent with observations, including distinctive signatures to be searched for in future observations. |

Regular Seminar Jeff Murugan (Cape Town U.)

at:16:30
room G.O. Jones 610 | abstract: We compute the holographic entanglement entropy for the pure gravitational anomaly in 3+1 dimensions. Using the perturbative method developed for com- puting entanglement entropy for quantum field theories, we also compute the parity odd contribution to the entanglement entropy of the dual field theory that comes from a background gravitational Chern-Simons term. We find that, in leading order in the perturbation of the background geometry, the two contribu- tions match except for a logarithmic divergent term on the field theory side. We interpret this extra contribution as encoding our ignorance of the source which creates the perturbation of the geometry. |

Regular Seminar Andrea Marzolla (Bruxelles U.)

at:14:00
room G.O. Jones 610 | abstract: Poincaré invariance imposes strong non-perturbative constraints on the dependence of scattering amplitudes on the kinematical variables. For massless external states, Benincasa and Cachazo have shown that the 3-point amplitude is fully determined up to a constant (the coupling). We extend their approach, based on the spinor-helicity formalism, to time-like momenta, and we find that, even when massive external states are involved, the functional form of the 3-point amplitude is fully determined, up to (several) constants. In this talk I review the derivation in the massless case, enlightening the role of the little group covariance of the amplitude in constraining its functional form, and the particularly simple form that these constraints get in the spinor language. Then I will show how to extend this procedure to the massive case, deriving the constraining equations for the massive little group, and eventually showing the expressions for 3-point amplitudes involving one, two, or three massive particles. |

Regular Seminar Alejandro Jenkins (Costa Rica U.)

at:14:00
room G.O. Jones 610 | abstract: A self-oscillator generates and maintains a periodic motion at the expense of an energy source with no corresponding periodicity. Small perturbations about equilibrium are amplified. Non-linearity accounts for steady-state oscillations and for the ability of coupled self-oscillators to exhibit both spontaneous synchronisation (“entrainment”) and chaos. The theory of self-oscillators has achieved its greatest sophistication in mathematical control theory and in the study of ordinary differential equations. I shall explain in this talk how an understanding better suited to physicists can be founded on considerations of energy, efficiency, and thermodynamic irreversibility. After reviewing the key differences between forced a parametric resonances on the one hand and self-oscillators on the other, I will comment on how a physical approach to the theory of self-oscillators throws new light on flow instabilities. I will close by describing mechanical and hydrodynamic analogs of the Zel’dovich superradiance of rotating black holes, a subject of considerable interest in high-energy physics today. |

Regular Seminar Andrius Stikonas (Edinburgh U.)

at:16:00
room G.O. Jones 610 | abstract: It is usually hard to compute entanglement entropy and mutual information for conformal field theories (CFT). Ryu-Takayanagi proposals allows us to find the same quantities using calculations in gravity. In this talk I will show how to find holographic entanglement entropy and scrambling time for BTZ black hole perturbed by a heavy (backreacting) particle. Holographic bulk description improves on the shock-wave approximation in 3d bulk dimensions. I will also discuss my work to generalize this calculation to the rotating BTZ black hole. |

Regular Seminar Carsten Schneider (RISC)

at:14:00
room G.O. Jones 610 | abstract: Symbolic summation started with Abramov's telescoping algorithm for rational functions (1971), was pushed further by Gosper's algorithm for hypergeometric expressions (1978) and reached its first peak level with Zeilberger's creative telescoping algorithm (1990) and Petkovsek's recurrence solver (1992) to treat definite hypergeometric sums. In this talk we focus on the difference ring approach which covers all these algorithms as special cases. Its foundation was lead by Karr's summation algorithm (1981) and has been pushed forward significantly within the last 18 years. In a long term project with DESY (Deutsches Elektronen-Synchrotron) the produced algorithms have been playing a central role to evaluate several hundred thousands of 2-loop and 3-loop massive Feynman integrals. In this talk we will elaborate by concrete examples how our advanced difference ring theory and the underlying algorithms encoded within the summation package Sigma are used to attack these highly complicated Feynman integrals. |

Regular Seminar Alessandro Pini (Oviedo U.)

at:14:00
room G.O. Jones 610 | abstract: In the first part of the talk I give an introduction to the computational tool called "Hilbert Series" (HS). I analyze how it can be employed for the characterization of the moduli space of vacua of a QFT and of the moduli space of instantons. Then, in the second part of the talk, I discuss the moduli space of (framed) self-dual instantons on CP^2. These are described by an ADHM-like construction which allows to compute the Hilbert Series of the moduli space. The latter has been found to be blind to certain compact directions. I probe these directions, finding them to correspond to a Grassmanian, upon considering appropriate ungaugings. Moreover I discuss the ADHM-like construction of instantons on CP^2/Z_n as well as compute its Hilbert series. As in the unorbifolded case, these turn out to coincide with those for instantons on C^2/Z_n. This talk is mainly based on https://arxiv.org/abs/1502.07876 . |