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)`

Regular Seminar Jim Halverson (Northeastern University in Boston)

at:14:00
room Zoom | abstract: We propose a theoretical understanding of neural networks in terms of Wilsonian effective field theory. The correspondence relies on the fact that many asymptotic neural networks are drawn from Gaussian processes, the analog of non-interacting field theories. Moving away from the asymptotic limit yields a non-Gaussian process and corresponds to turning on particle interactions, allowing for the computation of correlation functions of neural network outputs with Feynman diagrams. Minimal non-Gaussian process likelihoods are determined by the most relevant non-Gaussian terms, according to the flow in their coefficients induced by the Wilsonian renormalization group. This yields a direct connection between overparameterization and simplicity of neural network likelihoods. Whether the coefficients are constants or functions may be understood in terms of GP limit symmetries, as expected from 't Hooft's technical naturalness. General theoretical calculations are matched to neural network experiments in the simplest class of models allowing the correspondence. Our formalism is valid for any of the many architectures that becomes a GP in an asymptotic limit, a property preserved under certain types of training. |

Regular Seminar Emil Bjerrum-Bohr ( Niels Bohr Institute)

at:14:00
room Zoom | abstract: Gravity is a fundamental theory of physics, but so weak, that we still know very little about it. A new exciting development is that the Laser Interferometer Gravitational-Wave Observatory (LIGO) can now measure the effects when massive black holes collide in the Universe. This has stimulated many new and interesting studies of gravitational interactions. I will in this talk discuss recent computational advances and discuss how to derive results for observables in general relativity from amplitudes. |

Regular Seminar Minhyong Kim (University of Oxford)

at:14:00
room Zoom | abstract: Arithmetic geometry is the study *arithmetic schemes*, mathematical structures that have simultaneously an arithmetic and a geometric structure. The prototype is the so-called *spectrum of the integers* which is a geometric object on which the integers form the ring of functions. I will explain some of the difficult and classical problems that arise in their study, and how ideas of physics, especially topological quantum field theory, may be helpful. |

Regular Seminar Matthias Gaberdiel (ETH Zurich)

at:14:00
room Zoom | abstract: String theory on AdS3 x S3 x T4 with one unit of NS-NS flux is argued to be exactly dual to the symmetric orbifold of T4 in the large N limit. The string theory background can be described in terms of a solvable world-sheet theory. This allows one to compute the complete single-string spacetime spectrum and thereby demonstrate that it agrees with the that of the symmetric orbifold of T4. Furthermore, the structure of the symmetric orbifold correlators can be reproduced from the world-sheet perspective. |

Regular Seminar Frank Krauss (Durham University)

at:14:00
room Zoom | abstract: In my talk, I will introduce concepts relevant for simulation of LHC physics. I will highlight some of the challenges when going to the level of precision necessary to match experimental accuracy. |

Regular Seminar Masanori Hanada (University of Surrey)

at:14:00
room Zoom | abstract: We propose a unified description of two important phenomena: color confinement in large-N gauge theory, and Bose-Einstein condensation (BEC). We focus on the confinement/deconfinement transition characterized by the increase of the entropy from N^0 to N^2, which persists in the weak coupling region. Indistinguishability associated with the symmetry group --- SU(N) or O(N) in gauge theory, and S_N permutations in the system of identical bosons --- is crucial for the formation of the condensed (confined) phase. We relate standard criteria, based on off-diagonal long range order (ODLRO) for BEC and the Polyakov loop for gauge theory. The constant offset of the distribution of the phases of the Polyakov loop corresponds to ODLRO, and gives the order parameter for the partially-(de)confined phase at finite coupling. Furthermore we show the numerical evidence for this phenomenon at strong coupling, by using the Yang-Mills matrix model as a concrete example and solving it numerical via lattice simulation. This talk is based on a series of papers, especially "Color Confinement and Bose-Einstein Condensation" by Hanada, Shimada and Wintergerst, 2001.10459 [hep-th] and "Partial Deconfinement at Strong Coupling on a Lattice' by Bergner, Bodendorfer, Funai, Hanada, Rinaldi, Schaefer, Vranas and Watanabe to appear (should be in hep-th by the talk). |

Regular Seminar Damian Galante (King's College)

at:14:00
room Zoom | abstract: Cosmological (or de Sitter) horizons behave qualitatively different to black hole horizons and this poses a challenging problem in the context of holography. In this talk, I will discuss a novel construction to probe de Sitter horizons using the usual tools of the AdS/CFT correspondence. I will further explore ongoing efforts to reconstruct the bulk metric in two dimensions from the dual quantum mechanical correlators in the boundary. |

Regular Seminar Cyril Closset (Oxford)

at:14:00
room Zoom | abstract: I will explore aspects of the Coulomb-branch physics of five-dimensional superconformal field theories (SCFT). More precisely, I will consider the 5d SCFT on a circle, and describe the general structure of the Coulomb-branch BPS states as encoded in a "5d BPS quiver," which can be computed from standard string-theory geometric-engineering techniques. The interplay between 4d and 5d BPS quivers will play a central role in our story. |

Triangular Seminar Maissam Barkeshli (University of Maryland)

at:15:00
room G.O. Jones LT | abstract: Topological quantum field theories, which can be used to model topologically ordered phases of matter in quantum many-body systems, exhibit rich behavior in the presence of global symmetries. In this talk I will present progress over the last few years in understanding (2+1)D TQFTs in the presence of a global symmetry group G. This leads to a new mathematical structure, G-crossed braided tensor categories, that characterizes different possible patterns of symmetry fractionalization for topologically non-trivial particles and the fusion and braiding properties of symmetry defects. Two types of anomalies arise in the discussion: (1) "symmetry localization anomalies," which can also be interpreted as the theory possessing a non-trivial 2-group symmetry, and (2) symmetry fractionalization anomalies, which are equivalent to 't Hooft anomalies of the TQFT. I will describe various methods that have been developed in the past few years to compute these anomalies from the algebraic data that defines the TQFT and the symmetry action. |

Triangular Seminar Edgar Shaghoulian (Cornell University)

at:16:30
room G.O. Jones LT | abstract: The information paradox can be realized in two-dimensional models of gravity. In this setting, we show that the large discrepancy between the von Neumann entropy as calculated by Hawking and the requirement of unitarity is fixed by including new saddles in the gravitational path integral. These saddles arise in the replica method as wormholes connecting different copies of the black hole. |

Informal Seminar Seok Kim (Seoul National University)

at:10:30
room GOJ 610 | abstract: Cardy limit and large black holes; comments on generalizations and other examples |

Informal Seminar Seok Kim (Seoul National University)

at:10:30
room GOJ 610 | abstract: Indices and protected spectrum |

Informal Seminar Seok Kim (Seoul National University)

at:10:00
room GOJ 610 | abstract: Introduction: black hole thermodynamics; black holes in AdS; holographic viewpoint from (N=4 super) Yang-Mills |

Regular Seminar Seok Kim (Seoul National University)

at:14:00
room GO Jones 610 | abstract: I will explain the physics of BPS black holes in AdS/CFT in 4 and 3 dimensions, focussing on the deconfined phases of the field theories. |

Regular Seminar Sangmin Lee (Seoul National University)

at:14:00
room GO Jones 516 | abstract: Building upon recent progress in applying amplitude techniques to perturbative general relativity, we propose a closed-form formula for the conservative Hamiltonian of a spinning binary system at the 1st post-Minkowskian order. It is applicable for general spinning bodies with arbitrary spin multipole moments. It is linear in gravitational constant by definition, but exact to all orders in momentum and spin expansions. At each spin order, our formula implies that the spin-dependence and momentum dependence factorize completely. We compare our formula to a similar one derived in 2017 from a spinning test-body near a Kerr black hole and find perfect agreement. |

Regular Seminar Guilherme Franzmann (NORDITA)

at:14:00
room GO Jones 610 | abstract: Recently, all duality invariant α′ (alpha-prime)-corrections to the massless NS-NS sector of string theory on time-dependent backgrounds were classified and the form of their contribution to the action were calculated. In this talk we will see how to introduce matter sources in the resulting equations of motion in an O(d,d) covariant way. Then we show that either starting with the corrected equations and sourcing them with matter or considering corrections to the matter sourced lowest order equations give the same set of equations that defines string cosmology to all orders in α′. We also discuss perturbative and non-perturbative de Sitter solutions including matter, and explicitly show that de Sitter solutions are allowed non-perturbatively. |

Regular Seminar Jean Alexandre (King's College)

at:14:00
room G O Jones 610 | abstract: The work presented here explores the possibility of introducing non-Hermitian scalar and fermion mass terms, in addition to the usual Hermitian ones. The consistency of the resulting description requires a reworking of all the fundamental properties in Field Theory from the beginning, which is challenging but appears to be possible. |

Regular Seminar Madalena Lemos (CERN)

at:14:00
room G O Jones 610 | abstract: We study symmetry constraints on BPS surface defects in four-dimensional superconformal field theories, showing how supersymmetry imposes relations on anomaly coefficients. Turning to dynamics, we analyze a protected subsector of N=(2,2) surface defects that is captured by a two-dimensional chiral algebra. We discuss how to compute observables of interacting defects from the chiral algebra, including the aforementioned anomaly coefficients. |