This institute may be found at Strand in Central London, just north of the Thames (map).
Getting to the Strand Campus:
Temple (District and Circle lines): 2 minute walk. Charing Cross (Bakerloo and Northern lines): 10 minute walk, Embankment (District, Circle and Bakerloo lines): 10 minute walk, Waterloo (Jubilee, Northern, Bakerloo, Waterloo & City lines): 12 minute walk, Holborn (Central and Picadilly lines): 12 minute walk,Chancery Lane (Central line): use exit 4 - 15 minute walk.
Charing Cross: 9 minute walk. Waterloo: 12 minute walk. Waterloo East: 10 minute walk. Blackfriars: 12 minute walk.
Buses stopping outside the College: 1, 4, 26, 59, 68, 76, X68, 168, 171, 172, 176(24 hour), 188, 243 (24 hour), 341 (24 hour), 521, RV1.
For more information about public transportations in London, please visit http://www.tfl.gov.uk.
Found at least 20 result(s)
Regular Seminar Bernardo Zan (Princeton)
at: 13:45 room K0.16 | abstract: The Schwinger model is one of the simplest gauge theories, yet it is only solvable in the massless case. In order to obtain numerical results, the Kogut-Susskind lattice approach with staggered fermions is regularly used. I will show that, contrary to what it was believed, the lattice mass and the continuum mass are actually not the same, but they are related by a mass shift. This can be understood by considering the (anomalous) chiral symmetry in the massless case, and has the advantage of greatly improving convergence of the numerics. I will comment on the charge-q Schwinger model as well as the multiflavor Schwinger model. |
Regular Seminar Jeremy Mann (KCL)
at: 13:45 room K0.16 | abstract: In conformal field theory, the lightcone bootstrap is an analytic approach to solving the crossing equations of correlation functions. The blocks, namely the kinematical constituents of a crossing equation, must be computed near lightcone singularities and resumed. At four points, this culminates in the universal dynamics of a double-twist operator at large spin. While extensions to higher points have been recently studied, further progress has been hampered by our limited knowledge of the blocks. In this talk, I will review the first applications of conformal block integrability to the multipoint lightcone bootstrap, focusing on scalar five point functions for concrete expressions. First, starting from a Gaudin model, I will review the construction of an integrable system that determines blocks via differential equations and a boundary condition. These differential equations, and by extension the crossing equations, can be explicitly solved in lightcone limits. Finally, after summarizing the old and new results we obtain at five points, I will comment on what this may entail for universal triple-twist data in six point functions. This is based on my thesis work, as well as an upcoming paper with Lorenzo Quintavalle, Apratim Kaviraj and Volker Schomerus. |
Regular Seminar Simon Ekhammar ()
at: 13:45 room K0.20 | abstract: The Quantum Spectral Curve (QSC) is a powerful integrability-based method capable of computing the spectrum of planar N=4 SYM. It has also been generalised in many directions, for example to cusped Wilson lines and various deformations. The success of the QSC motivates trying to extend the formalism beyond N=4 to other theories. This requires the study of the underlying structure of the QSC, a so called analytic Q-system. To construct an analytic Q-system it is necessary to specify both its algebraic structure, usually encoded into QQ-relations, and its analytic properties. I will talk about recent work to study Q-systems beyond the ones relevant for N=4, discussing both their algebraic and analytic properties. In particular I will discuss the recent conjecture of a QSC for AdS3/CFT2 which non-trivially couples two different Q-systems. While the curve shares many features with the N=4 QSC it also offers new surprises and challenges. If this new curve can be brought under full control and further tested many interesting applications and generalisations are within reach. |
Regular Seminar Ines Varela Aniceto (University of Southampton )
at: 13:45 room K0.20 | abstract: Dissipative relativistic hydrodynamics is expected to describe the late times, thermalised behaviour of strongly coupled fluids such as a strongly coupled super Yang-Mills plasma. These systems are then accurately described by a hydrodynamic series expansion in small gradients. Surprisingly, this hydrodynamic expansion is accurate even when the systems are still quite anisotropic: the non-hydrodynamic modes governing the non-equilibrium behaviour at very early-times become exponentially close to the hydrodynamic solution in an early process called hydrodynamization. This early success is intimately related with the fact that the hydrodynamic expansion is asymptotic. The theory of transseries and resurgence explicitly shows how the non hydrodynamic modes are in fact encoded in this late-time expansion. In this talk we will focus on a MIS-type model and use exponentially accurate summations of the the late-time resurgent transseries to recover the behaviour of the fluid before hydrodynamisation, and effectively match it to any given initial non-equilibrium condition. We will further show that such summations can provide analytic predictions beyond the late time regime. |
Regular Seminar Vladimir Kazakov (ENS Paris)
at: 13:15 room K0.20 | abstract: I will speak about my recent work with Zechuan Zheng where we study the SU(Nc) lattice Yang-Mills theory in the t Hooft limit Nc -> infinity, at dimensions D=2,3,4, via the numerical bootstrap method. It combines the Makeenko-Migdal loop equations, with the cut-off L on maximal length of wilson loops, and the positivity conditions on certain correlation matrices. We thus obtain rigorous upper and lower bounds on plaquette average at various couplings. The results are quickly improving with the increase of the cutoff L. In particular, for D=4 and L=16, the upper bound data in the most interesting weak coupling phase are not far from the Monte-Carlo results and they reproduce well the 3-loop perturbation theory. We also attempt to extract the information about the gluon condensate from this data. Our results suggest that bootstrap can provide a tangible alternative to, so far uncontested, Monte Carlo approach. I will also mention our bootstrap results for an "unsolvable" two-matrix model in the large N limit, where this method appears to be superior in efficiency over Monte Carlo. |
Regular Seminar Pietro Ferrero (Mathematical Institute, Oxford University)
at: 13:45 room K0.20 | abstract: The insertion of local operators along a straight Maldacena Wilson line in planar N=4 super Yang Mills defines a defect supersymmetric conformal field theory in one dimension. This is a simple but interesting setup where one can combine field theory techniques such as bootstrap, integrability and localization, aiming at a full solution of a non-trivial quantum mechanical system. I will adopt a bootstrap approach and study correlation functions of local operators for large t Hooft coupling, where the system is dual to an open superstring in $AdS_5 \times S^5$. I will present results for the four-point function of the displacement multiplet of the 1d defect CFT corresponding to three-loop diagrams in AdS, which are obtained using a suitable position-space ansatz and after considering a large system of mixed correlators. The problem is made particularly hard by the large degeneracy of operators at strong coupling, which we solve by taking into account four-point functions with external unprotected operators. The simple 1d kinematics is an ideal toy model for bootstrap techniques of interest for higher-dimensional cases as well. The seminar will be based on published as well as ongoing work with Carlo Meneghelli (see arxiv:2103.10440). |
Regular Seminar Elizabeth Himwich (Harvard)
at: 13:45 room Online | abstract: The operator product expansion of massless celestial primary operators of arbitrary spin is investigated. PoincarÃ© symmetry is found to imply a set of recursion relations on the operator product expansion coefficients of the leading singular terms at tree-level in a holomorphic limit. The symmetry constraints are solved by an Euler beta function with arguments that depend simply on the right-moving conformal weights of the operators in the product. These symmetry-derived coefficients are shown not only to match precisely those arising from momentum-space tree-level collinear limits, but also to obey an infinite number of additional symmetry transformations that respect the algebra of w(1+infinity). In tree-level minimally-coupled gravitational theories, celestial currents are constructed from light transforms of conformally soft gravitons and found to generate the action of w(1+infinity) on arbitrary massless celestial primaries. Results include operator product expansion coefficients for fermions as well as those arising from higher-derivative non-minimal couplings of gluons and gravitons. |
Regular Seminar Adolfo R. Cisterna Roa (U. of Tarapaca/ U. of Trento)
at: 13:00 room TBC | abstract: We present a new family of exact four-dimensional Taub-NUT spacetimes in Einstein-Î› theory supplemented with a conformally coupled scalar field exhibiting a power-counting super-renormalizable potential. Our configurations are constructed in the following manner: A solution of a conformally coupled theory with a conformal potential, henceforth the seed (gÎ¼Î½,Ï†), is transformed by the action of a specific change of frame in addition with a simultaneous shift of the seed scalar field. The conformal factor of the transformation and the shift are both affine functions of the original scalar Ï†. The new configuration, (á¸¡Î¼Î½ , Ï†Ì„), solves the field equations of a conformally coupled theory with the extended aforementioned super-renormalizable potential, this under the presence of an effective cosmological constant. The new spectrum of solutions is notoriously enhanced with respect to the original seed containing regular black holes, wormholes, and bouncing cosmologies. We highlight the existence of two types of exact black bounces given by de Sitter and anti-de Sitter geometries that transit across three different configurations each. The de Sitter geometries transit from a regular black hole with event and cosmological horizons to a bouncing cosmology that connects two de Sitter Universes with different values of the asymptotic cosmological constant. An intermediate phase, which might be represented by two different configurations, takes place. These configurations are given by a de Sitter wormhole or by a bouncing cosmology that connects two de Sitter Universes, both under the presence of a cosmological horizon. On the other hand, the anti-de Sitter geometries transit from a regular black hole with inner and event horizons to a wormhole that connects two asymptotic boundaries with different constant curvatures. The intermediate phase is given in this case by an anti-de Sitter regular black hole with a single event horizon. This regular black hole might appear in two different configurations. As a regular anti-de Sitter black hole inside of an anti-de Sitter wormhole or as an anti-de Sitter regular black hole with a cosmological bounce in its interior. All these geometries are shown to be smoothly connected by the mass parameter only. Other standard stationary black holes, bouncing cosmologies and wormholes are also identified. |
Regular Seminar Jakob Salzer (Brussels U.)
at: 13:45 room K0.20 | abstract: General Relativity in asymptotically flat spacetimes gives rise to an infinite number of symmetries which form the celebrated BMS group comprising superrotations and supertranslations. These symmetries are closely related to soft theorems of gravitational scattering amplitudes. Recently it was shown that supertranslations and superrotations are only the lowest levels of a whole tower of symmetries of tree level gravitational scattering amplitudes that form a w_{1+\infty} algebra. The fate of this symmetry once loop effects are taken into account is currently unknown. In this talk I will review the emergence of this symmetry algebra based on the celestial CFT program and argue that the w_{1+\infty} algebra persists quantum corrections in self-dual gravity. This talk is based on 2111.10392 with A.Ball, S. Narayanan, and A. Strominger. |
Regular Seminar Jose Figueroa-O'Farrill (University of Edinburgh)
at: 13:45 room Online | abstract: I will discuss recent and ongoing work with Emil Have, Stefan Prohazka and Jakob Salzer on possible kinematics for flat space holography. I will discuss how a seemingly novel projective compactification of Minkowski spacetime reveals a rich asymptotic geometry homogeneous under the Poincare group and including the blow-ups at spatial and timelike infinities as well as a novel four-dimensional space intimately associated to null infinity. This allows for novel geometric descriptions of the Minkowski asymptotic geometries and gives us a glimpse of the asymptotic geometry of asymptotically flat spaces. |
Regular Seminar Irene Valenzuela (CERN)
at: 13:45 room k0.20 | abstract: Consistency with quantum gravity can impose non-trivial constraints at low energies, even if the Planck scale is at very high energy. The Swampland program aims to determine the constraints that an effective field theory must satisfy to be consistent with a UV embedding in a quantum gravity theory. One of the most important swampland conditions is the presence of infinite towers of states becoming massless at the weak coupling/large field limits. This has been extensively tested in string theory compactifications, but a bottom-up explanation was missing. In this talk I will provide a possible explanation based on finiteness of black hole entropy. I will also explain how several wampland criteria, including the Weak Gravity Conjecture, Distance Conjecture and bounds on the finiteness of the quantum gravity vacua, may be more fundamentally a consequence of the finiteness of quantum gravity amplitudes. |
Regular Seminar Eleni Kontou (University of Amsterdam)
at: 13:45 room k0.20 | abstract: The classical singularity theorems predict the existence of singularities, defined using incomplete geodesics, under a set of general assumptions. One of those assumptions, namely the energy condition, is always violated by quantum fields and thus the realm of semiclassical gravity is outside the scope of these theorems. However, quantum fields do obey weaker conditions which can also be used to predict singularities. In this talk, I will present derivations of such semiclassical singularity theorems both in the timelike and the null case and discuss the challenges and open questions for each case. |
Regular Seminar Avner Karasik (Cambridge Univ. DAMTP)
at: 13:45 room K0.20 | abstract: 4d gauge theories with massless fermions typically have axial U(1) transformations that suffer from the ABJ anomaly. One can modify the theory of interest by adding more fields in a way that restores the axial symmetry, and use it to derive rigorous 't-Hooft anomaly matching conditions. These conditions are not valid for the original theory of interest, but for the modified theory. I will show that the modification can be done in a specific way that allows us to relate the dynamics of the modified theory to the dynamics of the original theory. In this way, the anomaly matching conditions of the modified theory can be used to learn new things on the original theory even though they involve axial transformations which are not a symmetry of the original theory. In the talk I will describe this method and discuss some applications to various examples. |
Regular Seminar Sean Hartnoll (Cambridge Univ. DAMTP)
at: 13:45 room K0.20 | abstract: Quantum mechanical theories describing large N by N matrices of oscillators can lead to an emergent space as N -> infinity. In the most fully fledged version, the emergent space is dynamical and gravitating. However, there are also simpler, lower dimensional versions of this phenomenon. One of the simplest occurs in the so-called quantum Hall matrix model, in which a 2 dimensional space emerges and supports Chern-Simons dynamics. I will describe how this solvable model leads to insights about the emergence of space from matrices. In particular, I will describe how the emergent spatial locality is reflected in the entanglement structure of the ground state of theory. |