Exceptional Seminar Shai Chester (Weizmann Institute of Science)

at:14:30
room G O Jones 610 | abstract: We apply two non-perturbative methods, the numerical conformal bootstrap and supersymmetric localization, to four point functions of half-BPS operators in 3d maximally supersymmetric ABJM theory. This correlator is dual to scattering of gravitons and KK-modes in M-theory on AdS_4 x S^7, and determines the M-theory S-matrix in the flat space limit. Using localization, we compute OPE coefficients of certain protected operators exactly at small N and to all orders in 1/N at large N. We apply these analytic results to the numerical bootstrap in two ways. First, we find that numerical bootstrap bounds for these OPE coefficients are saturated by the analytic results, which allows us to read off all low-lying CFT data in the correlator, including for unprotected operators. Second, by imposing the analytical results we find precision islands in the space of certain quarter and eighth BPS OPE coefficients. This numerical data can be used to determine the M-theory S-matrix, which we confirm at leading order in large N. |

Regular Seminar Hadi Godazgar (AEI)

at:13:15
room S2.29 | abstract: I will review asymptotic charges in electromagnetism and explain why they are physical. Then I will review BMS charges in asymptotically flat spacetimes and show that there are in fact magnetic analogues of BMS charges that had been overlooked in the literature. I will comment on the implications of these newly found charges. |

Exceptional Seminar Falk Hassler (University of Oviedo)

at:14:00
room G O Jones 610 | abstract: Generalised Scherk-Schwarz reductions are a powerful tool to construct consistent truncations in Double and Exceptional Field Theories. Recently, it turned out that they are also closely related to Poisson-Lie T-duality. However, the most general form of Poisson-Lie T-duality, the dressing coset construction, can not be implemented in terms of a generalised Scherk-Schwarz ansatz. I will show that implementing it in generalised geometry leads to a natural extension of the generalised Scherk-Schwarz ansatz which comes with many new features: 1) Partial or full breaking of SUSY which allows to find many new examples of generalised Kähler or Calabi-Yau Manifolds. 2) Singular backgrounds with localised sources. 3) Localised vector multiplets while still resulting in consistent truncations. |

Conference A workshop (City, University of London)

at:10:30
room ELG03 | abstract: This workshop gives a flavour of where and how different types of symmetries are employed in the modern context of quantum theories. The workshop will cover the interplay between discrete (CPT) and continuous Lie group symmetries. For instance, conformal symmetries in the form of infinite-dimensional Virasoro in quantum field theories, Kac-Moody algebras in the study of string sigma-models, Lorentzian Kac-Moody algebras (e.. E11) in the description of string and brane theories, and quantum group symmetries in the study of integrable systems. Speakers: Andrea Cavaglia (King's College London) Anastasia Doikou (Heriot-Watt University, Edinburgh) Valentina Forini (City, University of London) Vidas Regelskis (University of Hertfordshire and Vilnius University) Takanobu Taira (City, University of London) Peter West (King's College London) https://cityagm.weebly.com/ |

Regular Seminar Claudia de Rham (Imperial College London)

at:14:00
room G O Jones 610 | abstract: The recent direct detection of gravitational waves marks the beginning of a new era for physics and astronomy with an opportunity the probe gravity at its most fundamental level and have already been used to successfully constrain or rule out many effective field theories relevant for cosmology. I will discuss the strengths and limitations of these constraints and explore other complementary approaches in segregating between various effective field theories. |

Exceptional Seminar Salvish Goomanee (ENS Lyon)

at:11:00
room K4.31 | abstract: In this talk I will present the novel developments pertaining the the thermodynamics of the XXZ spin-1/2 chain. I will describe the analysis allowing one to prove several features related to the behaviour of the Heisenberg-Ising (or XXZ) spin-1/2 chain at finite temperature. It has been argued in the literature that the per-site free energy or the correlation length admit integral representations whose integrands are expressed in terms of solutions of non-linear integral equations. The derivations of such representations rested on various unproven conjectures such as the existence of a real, non-degenerate, maximal in modulus Eigenvalue of the quantum transfer matrix, the existence and uniqueness of the solutions to the auxiliary non-linear integral equations in the infinite Trotter limit. I will show how these conjectures can be proven in a rigorous setting for temperatures high enough. The result of these analyses allowed one to observe that a subset of sub-dominant Eigenvalues of the quantum transfer matrix admits a large temperature asymptotic expansion. |