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Seminars at

Found at least 20 result(s)

28.04.2022 (Thursday)

Comments on Summing over Bordisms in TQFT

Journal Club Anindya Banerjee (Rutgers)

at:
16:00 Other
room Online
abstract:

Recent works in quantum gravity, motivated by the factorization problem and baby universes, have considered sums over bordisms with fixed boundaries in topological quantum field theory. I will discuss this construction, its scope and its limitations, and describe the total amplitude in this class of theories in terms of a curious splitting formula; Part of the London TQFT Journal Club; it will be possible to follow this talk online (please register at https://london-tqft.co.uk)

14.04.2022 (Thursday)

Simulation of quantum field theories by quantum computers

Journal Club Zhenghan Wang (Microsoft Station Q and UC Santa Barbara)

at:
16:00 Other
room Online
abstract:

The quantum Church-Turing thesis would imply that there is a unique model of quantum computing. It follows that quantum computers could simulate quantum field theories efficiently.After a review on the simulation of topological quantum field theories, we will focus on a lattice approach to conformal field theories from anyonic chains.; it will be possible to follow this talk online (please register at https://london-tqft.co.uk)

14.04.2022 (Thursday)

Line Operators in Chern-Simons-Matter Theories and Bosonization in Three Dimensions

Journal Club Amit Sever (Tel Aviv University)

at:
14:45 Other
room Zoom, instructions in abstract
abstract:

We study Chern-Simons theories at large N with either bosonic or fermionic matter in the fundamental representation. The most fundamental operators in these theories are mesonic line operators, the simplest example being Wilson lines ending on fundamentals. We classify the conformal line operators along an arbitrary smooth path as well as the spectrum of conformal dimensions and transverse spins of their boundary operators at finite 't Hooft coupling. These line operators are shown to satisfy first-order chiral evolution equations, in which a smooth variation of the path is given by a factorized product of two line operators. We argue that this equation together with the spectrum of boundary operators are sufficient to uniquely determine the expectation values of these operators. We demonstrate this by bootstrapping the two-point function of the displacement operator on a straight line. We show that the line operators in the theory of bosons and the theory of fermions satisfy the same evolution equation and have the same spectrum of boundary operators. ----- Part of the London Integrability Journal Club. If you are a new participant please register at integrability-london.weebly.com. Link emailed on Tuesday.

11.04.2022 (Monday)

A playful intro to some modern geometry

Informal Seminar Yang-Hui He (LIMS and City)

at:
10:30 Other
room LIMS, Royal Institution
abstract:

With a view towards constructing Calabi Yau manifolds, we present some rudiments of the intersection between algebraic, differential and arithmetic geometry. Throughout we will take the opposite of the Bourbaki approach and work through explicit examples, rather than to emphasise on the theory.

07.04.2022 (Thursday)

JTbar - deformed CFTs as non-local CFTs

Journal Club Monica Guica (IPhT Saclay)

at:
14:45 Other
room Zoom, instructions in abstract
abstract:

TTbar and JTbar - deformed CFTs provide an interesting example of non-local, yet UV-complete two-dimensional QFTs that are entirely solvable. I will start by showing that both classes of theories possess Virasoro x Virasoro or Virasoro- Kac- Moody x Virasoro - Kac- Moody symmetry. For the case of JTbar, I will discuss the classical realization of these symmetries in terms of field-dependent coordinate transformations and show how the associated generators can be used to define an analogue of "primary" operators in this non-local theory, whose correlation functions are entirely fixed in terms of those of the undeformed CFT. In particular, two and three-point functions are simply given by the corresponding momentum-space correlator in the undeformed CFT, with all dimensions replaced by particular momentum-dependent conformal dimensions. Interestingly, scattering amplitudes off the near-horizon of extremal black holes are known to take a strikingly similar form. -------- Part of the London Integrability Journal Club. If you are a new participant please register at integrability-london.weebly.com. Link emailed on Tuesday.

04.04.2022 (Monday)

A playful introudction to some modern geometry

Informal Seminar Yang-Hui He (LIMS and City)

at:
10:30 Other
room LIMS, Royal Institution
abstract:

With a view towards constructing Calabi Yau manifolds, we present some rudiments of the intersection between algebraic, differential and arithmetic geometry. Throughout we will take the opposite of the Bourbaki approach and work through explicit examples, rather than to emphasise on the theory.

31.03.2022 (Thursday)

Numerical evidence for a Haagerup conformal field theory

Journal Club Ying-Hsuan Lin (Harvard)

at:
12:00 Other
room Online
abstract:

We numerically study an anyon chain based on the Haagerup fusion category, and find evidence that it leads in the long-distance limit to a conformal field theory whose central charge is ~2; it will be possible to follow this talk online (please register at https://london-tqft.co.uk)

28.03.2022 (Monday)

LonTI: A Playful Introduction to Some Modern Geometry

Regular Seminar Yang-Hui He (LIMS and City)

at:
10:30 Other
room LIMS, Royal Institution
abstract:

With a view towards constructing Calabi Yau manifolds, we present some rudiments of the intersection between algebraic, differential and arithmetic geometry. Throughout we will take the opposite of the Bourbaki approach and work through explicit examples, rather than to emphasise on the theory.

28.03.2022 (Monday)

Quantifying Intelligence Mathematically

Colloquium Peter Cochrane (University of Suffolk)

at:
13:30 Other
room LIMS, Royal Institution
abstract:

ABS: TBC NB: The colloquium will follow naturally on from the LonTI lecture and there will be refreshments. BIO: Professor Peter Cochrane, DSc, OBE, is Professor of Sentient Systems at the University of Suffolk, and visiting Professor to The University of Hertfordshire, Salford, and Nottingham Trent University has received numerous awards including the IEEE Millennium Medal, Martlesham Medal, Prince Philip Medal, Queens Award for Export and Technology and an OBE by The Queen in 1999. He retired from BT as CTO in 2000 to form his own consultancy company. This saw the founding of eBookers, Shazam Entertainment, and a raft of smaller start ups. Peter has also seen assignments with UK, Singapore and Qatar government departments; HP, Motorola, 3M, Dupont, Ford, Sun, Apple, Cisco, Rolls Royce, BMW, Jersey Tel, Chorus, FaceBook, et al.

24.03.2022 (Thursday)

Liouville on the lattice

Journal Club David Vegh (QMUL)

at:
12:00 Other
room G.O. Jones 610
abstract:

The Liouville equation has many applications: it describes surfaces of constant negative curvature and plays an important role in non-critical string theory. In this talk we discuss how to put the Liouville equation on the lattice in a completely integrable way; it will be possible to follow this talk online (please register at https://london-tqft.vercel.app)

21.03.2022 (Monday)

LonTI: A Playful Introduction to Some Modern Geometry

Regular Seminar Yang-Hui He (LIMS and City)

at:
10:30 Other
room LIMS, Royal Institution
abstract:

With a view towards constructing Calabi Yau manifolds, we present some rudiments of the intersection between algebraic, differential and arithmetic geometry. Throughout we will take the opposite of the Bourbaki approach and work through explicit examples, rather than to emphasise on the theory. Address: 21 Albemarle St, London W1S 4BS Floor 2: London Institute of Mathematical Sciences (LIMS)

17.03.2022 (Thursday)

A QFT for non-semisimple TQFT

Journal Club Tudor Dimofte (UC Davis and U. Edinburgh)

at:
16:00 Other
room Zoom
abstract:

Topological twists of 3d N=4 gauge theories naturally give rise to non-semisimple 3d TQFT's. In mathematics, prototypical examples of the latter were constructed in the 90's (by Lyubashenko and others) from representation categories of small quantum groups at roots of unity; they were recently generalized in work of Costantino-Geer-Patureau Mirand and collaborators. I will introduce a family of physical 3d quantum field theories that (conjecturally) reproduce these classic non-semisimple TQFT's. The physical theories combine Chern-Simons-like and 3d N=4-like sectors. They are also related to Feigin-Tipunin vertex algebras, much the same way that Chern-Simons theory is related to WZW vertex algebras. (Based on work with T. Creutzig, N. Garner, and N. Geer.); part of the London TQFT Journal Club; it will be possible to follow this talk online (please register at https://london-tqft.vercel.app)

14.03.2022 (Monday)

LonTI: On the SYK model and the Emergence of Spacetime

Regular Seminar Damian Galante (KCL)

at:
10:30 Other
room Royal Institute of Great Britain
abstract:

In these lectures, we will present to seemingly different theories. The first one is a theory of gravity in two dimensions, called Jackiw-Teitelboim (JT) gravity, that is relevant in the context of higher-dimensional, near-extremal black holes. The second one is a quantum mechanical theory of fermions, with no gravity, called the Sachdev, Ye and Kitaev (SYK) model. We will explore precisely how JT gravity emerges from the SYK model by studying their actions, correlation functions and thermodynamic properties. This constitutes the simplest toy model of what theoretical physicists now call the holographic principle. Address: 21 Albemarle St, London W1S 4BS Floor 2: London Institute of Mathematical Sciences (LIMS)

10.03.2022 (Thursday)

Liouville conformal field theory: from probability theory to the conformal bootstrap

Journal Club Vincent Vargas (ENS, Paris)

at:
12:00 Other
room G.O. Jones 610
abstract:

Liouville conformal field theory (LCFT) was introduced by Polyakov in 1981 as an essential ingredient in his path integral construction of string theory. Since then Liouville theory has appeared in a wide variety of contexts ranging from random conformal geometry to 4d Yang-Mills theory with supersymmetry. Recently, a probabilistic construction of LCFT on general Riemann surfaces was provided using the 2d Gaussian Free Field. This construction can be seen as a rigorous construction of the 2d path integral introduced in Polyakov's 1981 work. In contrast to this construction, modern conformal field theory is based on representation theory and the so-called bootstrap procedure (based on recursive techniques) introduced in 1984 by Belavin-Polyakov-Zamolodchikov. In particular, a bootstrap construction for LCFT has been proposed in the mid 90's by Dorn-Otto-Zamolodchikov-Zamolodchikov (DOZZ) on the sphere. The aim of this talk is to review a recent series of work which shows the equivalence between the probabilistic construction and the bootstrap construction of LCFT on general Riemann surfaces. In particular, the equivalence is based on showing that LCFT satisfies a set of natural geometric axioms known as Segal's axioms; part of the London TQFT Journal Club; it will be possible to follow this talk online (please register at https://london-tqft.vercel.app)

10.03.2022 (Thursday)

Bootstrapping N = 4 super-Yang-Mills on the conformal manifold

Journal Club Shai Chester (Weizmann Institute)

at:
14:45 Other
room Zoom, instructions in abstract
abstract:

We study the N = 4 SYM stress tensor multiplet 4-point function for any value of the complexified coupling tau, and in principle any gauge group (we focus on SU(2) and SU(3) for simplicity). By combining non-perturbative constraints from the numerical bootstrap with two exact constraints from supersymmetric localization, we are able to compute upper bounds on low-lying CFT data (e.g. the Konishi) for any value of tau. These upper bounds are very close to the 4-loop weak coupling predictions in the appropriate regime. We also give preliminary evidence that these upper bounds become small islands under reasonable assumptions, in which case our method would provide a numerical solution to N = 4 SYM for any gauge group and tau. -------- Part of the London Integrability Journal Club. Please register at integrability-london.weebly.com if you are a new participant.

07.03.2022 (Monday)

LonTI: On the SYK model and the Emergence of Spacetime

Regular Seminar Damian Galante (KCL)

at:
10:30 Other
room Royal Institution of Great Britain
abstract:

In these lectures, we will present to seemingly different theories. The first one is a theory of gravity in two dimensions, called Jackiw-Teitelboim (JT) gravity, that is relevant in the context of higher-dimensional, near-extremal black holes. The second one is a quantum mechanical theory of fermions, with no gravity, called the Sachdev, Ye and Kitaev (SYK) model. We will explore precisely how JT gravity emerges from the SYK model by studying their actions, correlation functions and thermodynamic properties. This constitutes the simplest toy model of what theoretical physicists now call the holographic principle. Address: 21 Albemarle St, London W1S 4BS Floor 2: London Institute of Mathematical Sciences (LIMS)

03.03.2022 (Thursday)

Homogeneous Yang-Baxter deformations as undeformed yet twisted models

Journal Club Riccardo Borsato (Santiago de Compostela U., IGFAE)

at:
14:45 Other
room Zoom, instructions in abstract
abstract:

I will review recent progress in the study of a class of integrable deformations of sigma models known as "homogeneous Yang-Baxter". These deformations can be understood as generalisations of the well known TsT transformations. In fact, rather than deformations, the homogeneous Yang-Baxter procedure too can be reinterpreted as imposing twisted worldsheet boundary conditions in the undeformed sigma model. I will explain how to construct the twist in the generic case, which generalises the twist of TsT from abelian to non-abelian. I will also use the expression for the twist to discuss the construction of the classical spectral curve in some examples. To conclude, I will mention some open questions related to the quantum integrability of these models. ----------- Part of the London Integrability Journal Club. Please register at integrability-london.weebly.com if you are a new participant. The link will be emailed on Tuesday.

28.02.2022 (Monday)

LonTI: On the SYK model and the Emergence of Spacetime

Regular Seminar Damian Galante (KCL)

at:
10:30 Other
room Royal Institution of Great Britain
abstract:

In these lectures, we will present to seemingly different theories. The first one is a theory of gravity in two dimensions, called Jackiw-Teitelboim (JT) gravity, that is relevant in the context of higher-dimensional, near-extremal black holes. The second one is a quantum mechanical theory of fermions, with no gravity, called the Sachdev, Ye and Kitaev (SYK) model. We will explore precisely how JT gravity emerges from the SYK model by studying their actions, correlation functions and thermodynamic properties. This constitutes the simplest toy model of what theoretical physicists now call the holographic principle. Address: 21 Albemarle St, London W1S 4BS Floor 2: London Institute of Mathematical Sciences (LIMS)

24.02.2022 (Thursday)

Every conformal net has an associated VOA

Regular Seminar Andre Henriques (Oxford)

at:
12:00 Other
room G.O. Jones 610
abstract:

We show that every conformal net has an associated vertex algebra, thus identifying the class of conformal nets with a sub-class of the class of unitary vertex algebras. We also characterise those unitary vertex algebras that arise from a conformal net. (We conjecture that every unitary vertex algebras arises in this way, and hence that there is a bijective correspondence between conformal nets and unitary vertex algebras.) To construct the correspondence between conformal nets and unitary vertex algebras, we introduce a new notion of "field localised in a segment embedded in a Riemann surface", which could be of independent interest. This is joint work with James Tener; Part of the London TQFT Journal Club; it will be possible to follow this talk online (please register at https://london-tqft.vercel.app)

24.02.2022 (Thursday)

Crosscap States in Integrable Theories

Regular Seminar Joao Caetano (CERN)

at:
14:45 Other
room Zoom, instructions in abstract
abstract:

In this talk, I will describe crosscap states in integrable field theories and spin chains in 1+1 dimensions. I will derive an exact formula for overlaps between the crosscap state and any excited state in integrable field theories with diagonal scattering. I will then compute the crosscap entropy, i.e. the overlap for the ground state, in some examples. In the examples analyzed, the result turns out to decrease monotonically along the renormalization group flow except in cases where the discrete symmetry is spontaneously broken in the infrared. I will discuss crosscap states in integrable spin chains, and obtain determinant expressions for the overlaps with energy eigenstates. I will comment on the realization of crosscap states in holography. ----------- Part of the London Integrability Journal Club. Please register at integrability-london.weebly.com if you are a new participant. The link will be emailed on Tuesday.