Directions

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.

Seminars at Queen Mary University of London

Found at least 20 result(s)

21.10.2021 (Thursday)

The Principles of Deep Learning Theory

Regular Seminar Dan Roberts (MIT)

at:
14:00 QMW
room zoom
abstract:

[for zoom link please email s.nagy@qmul.ac.uk] Deep learning is an exciting approach to modern artificial intelligence based on artificial neural networks. The goal of this talk is to provide a blueprint — using tools from physics — for theoretically analyzing deep neural networks of practical relevance. This task will encompass both understanding the statistics of initialized deep networks and determining the training dynamics of such an ensemble when learning from data. In terms of their "microscopic" definition, deep neural networks are a flexible set of functions built out of many basic computational blocks called neurons, with many neurons in parallel organized into sequential layers. Borrowing from the effective theory framework, we will develop a perturbative 1/n expansion around the limit of an infinite number of neurons per layer and systematically integrate out the parameters of the network. We will explain how the network simplifies at large width and how the propagation of signals from layer to layer can be understood in terms of a Wilsonian renormalization group flow. This will make manifest that deep networks have a tuning problem, analogous to criticality, that needs to be solved in order to make them useful. Ultimately we will find a "macroscopic" description for wide and deep networks in terms of weakly-interacting statistical models, with the strength of the interactions between the neurons growing with depth-to-width aspect ratio of the network. Time permitting, we will explain how the interactions induce representation learning. This talk is based on a book, "The Principles of Deep Learning Theory," co-authored with Sho Yaida and based on research also in collaboration with Boris Hanin. It will be published next year by Cambridge University Press.

14.10.2021 (Thursday)

Lessons and surprises from Kaluza-Klein spectra

Regular Seminar Gabriel Larios (UAM)

at:
14:00 QMW
room zoom
abstract:

[foor zoom link please email s.nagy@qmul.ac.uk] Infinite towers of massive modes arise for every compactification of higher dimensional theories. Understanding the properties of these Kaluza-Klein towers on non-trivial solutions with an AdS factor has been a longstanding issue with clear holographic interest, as they describe the spectrum of single-trace operators of the dual CFTs at strong coupling and large N. In this talk, I will focus on two classes of solutions of such kind. The first class consists of AdS4 solutions of D=11 and Type II supergravity that can be obtained from maximal gauged supergravities in D=4. For the later part, I will describe new families of solutions in N=(1,1) supergravity in D=6 which uplift from half-maximal supergravity in D=3. In both cases, the spectra can be computed using recent techniques from Exceptional Field Theory, and the information thus obtained leads to several unexpected conclusions.

07.10.2021 (Thursday)

The Gravitino and the Swampland

Regular Seminar Dieter Lust (Munich)

at:
14:00 QMW
room zoom
abstract:

[for zoom details please email s.nagy@qmul.ac.uk] In this talk we discuss a new swampland conjecture stating that the limit of vanishing gravitino mass corresponds to the massless limit of an infinite tower of states and to the consequent breakdown of the effective field theory. The proposal can be tested in large classes of models coming from compactification of string theory to four dimensions, where we identify the Kaluza-Klein nature of the tower of states becoming light. We point out a general relation between the gravitino mass and an abelian gauge coupling, which allows us to connect our conjecture to the weak gravity conjecture or the absence of global symmetries in quantum gravity. We discuss phenomenological implications of our conjecture in (quasi-)de Sitter backgrounds and extract a lower bound for the gravitino mass in terms of the Hubble parameter.

06.10.2021 (Wednesday)

Constructing the 6 Loop 4 Point N=4 super-Yang-Mills Integrand

Journal Club Alex Edison (Uppsala U.)

at:
16:00 QMW
room G.O. Jones 610
abstract:

In this talk, we'll discuss the current state-of-the-art for constructing multi-loop integrands in N=4 super-Yang-Mills. After briefly covering some of the key goals, background, and ideas behind the multiloop integrand program, we turn to the cutting edge: constructing the complete (planar and non-planar) integrand for the six-loop four-point amplitude in maximal $D\le10$ super-Yang-Mills. This construction employs new advances that combat the proliferation of loops and state-sums when evaluating multi-loop $D$-dimensional unitarity cuts. Concretely, it uses two graph-based approaches, applicable in a range of theories, to evaluating generalized unitarity cuts in $D$ dimensions: 1) recursively from lower-loop cuts, or 2) directly from known higher-loop planar cuts. Neither method relies on explicit state sums or any sewing of tree-level amplitudes. The first method meshes particularly well with the Method of Maximal Cuts to allow direct construction of the complete six-loop integrand.

29.07.2021 (Thursday)

Integrability and chaos in SYM theories from anomalous-dimension spectra

Regular Seminar Anne Spiering (Trinity College Dublin)

at:
14:00 QMW
room zoom
abstract:

The discovery of integrability in planar N=4 SYM theory led to considerable advances in the computation of its planar anomalous dimension spectrum. Less is known at the non-planar level where the theory is assumed to be non-integrable. I will show how statistical properties of numerical anomalous dimension spectra can give insight into the symmetries of the underlying model and that the N=4 SYM non-planar spectrum and its beta-deformed version are well described by random matrix theory, indicating their quantum-chaotic nature. Doing so I will also discuss on-going work on using on-shell methods to obtain the dilatation operator for deformed versions of N=4 SYM theory. [for zoom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

22.07.2021 (Thursday)

Tidal effects from quantum field theory

Regular Seminar Kays Haddad (Niels Bohr Institute)

at:
14:00 QMW
room zoom
abstract:

Recently there has been great success in describing the inspiral phase of compact binary coalescence in General Relativity (GR) using scattering amplitudes. These efforts aim to improve the precision of gravitational wave (GW) templates used by detectors to identify GW events and test GR. The majority of this work has focused on describing a pair of objects that do not tidally deform. However real objects do tidally deform, and future GW detectors will be increasingly sensitive to such deformations. It has been shown that scattering amplitudes are applicable to the description of tidal effects as well. In this talk we discuss the application of the Hilbert series to the characterization of an entire class of tidal effects: those involving two powers of the Weyl tensor and objects with spin 0 and 1/2. The Hilbert series guides us in the construction of actions describing these effects, which we then use to calculate the leading-PM tidal scattering amplitude. With the amplitude in hand, we compute several classical quantities and compare to the literature where possible. [for zooom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

13.05.2021 (Thursday)

BPS states and RG flows

Regular Seminar Michele Del Zotto (Uppsala U.)

at:
14:00 QMW
room zoom
abstract:

The study of possible constraints on RG flows is an important question in our understanding of quantum field theory. In this talk I will discuss a constraint which arises by considering the spectrum of BPS excitations (an H-theorem). Examples are found in the context of four-dimensional supersymmetric quantum field theories with enough supersymmetry that the BPS spectrum is explicitly computable. Among others, we will discuss applications in the context of Maruyoshi-Song flows. [for zoom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

06.05.2021 (Thursday)

Towards a general map from Navier-Stokes to Maxwell via Einstein

Regular Seminar Cynthia Keeler (ASU)

at:
15:00 QMW
room zoom
abstract:

[for zoom link please email s.nagyATqmul.ac.uk] After a brief review of the cutoff-surface formulation of fluid-gravity duality, we explore the ``square root'' of the fluid-dual metrics via the classical-double copy, highlighting the constant vorticity flows and potential flows which have algebraically special Weyl double copy fields. We then present progress towards building the same map, from fluid solutions to gravitational solutions to Maxwell solutions, for generic fluids in 2+1 dimensions. This talk is based on JHEP 08 (2020) 147 published with ASU students Nikhil Monga and Tucker Manton, and forthcoming work.

29.04.2021 (Thursday)

The Topology of Data: from String Theory to Cosmology to Phases of Matter

Regular Seminar Gary Shiu (Wisconsin U., Madison)

at:
15:00 QMW
room zoom
abstract:

Abstract: We are faced with an explosion of data in many areas of physics, but very so often, it is not the size but the complexity of the data that makes extracting physics from big datasets challenging. As I will discuss in this talk, data has shape and the shape of data encodes the underlying physics. Persistent homology is a tool in computational topology developed for quantifying the shape of data. I will discuss three applications of topological data analysis: 1) identifying structure of the string landscape, 2) constraining cosmological parameters from CMB measurements and large scale structures data, and 3) detecting and classifying phases of matter. Persistent homology condenses these datasets into their most relevant (and interpretable) features, so that simple statistical pipelines are sufficient in these contexts. This suggests that TDA can be used in conjunction with machine learning algorithms and improves their architecture. [for zoom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

22.04.2021 (Thursday)

Boundary-bulk relations in conformal/topological field theories

Regular Seminar Liang Kong (Shenzhen Institute of Quantum Science and Engineering, SUSTech)

at:
14:00 QMW
room zoom
abstract:

[There will be a pre-seminar for students starting at 13:30. For zoom link please email s.nagyATqmul.ac.uk] The relation between the physics of the bulk and that of a boundary plays an important role in quantum field theories, quantum gravity and condensed matter physics. In this talk, I will review a manifestation of this relation that can be summarized as a short statement: "the bulk is the center of a boundary". I will explain the meaning of "center" and provide a formal proof of this statement (arXiv:1702.00673). By including higher codimensional domain walls between boundaries, the boundary-bulk relation can be formulated mathematically as a higher functor. In lower dimensional cases, it becomes precise mathematical theorems. In the end, I will discuss the significances of this relation in the study of topological orders and topological phase transitions.

15.04.2021 (Thursday)

A CFT Distance Conjecture

Regular Seminar Eric Perlmutter (IPhT)

at:
14:00 QMW
room zoom
abstract:

[for zoom link, please email s.nagyATqmul.ac.uk] We formulate conjectures relating the geometry of conformal manifolds to the spectrum of local operators in conformal field theories in d>2 spacetime dimensions. We focus on conformal manifolds with limiting points at infinite distance with respect to the Zamolodchikov metric. Our central conjecture is that all theories at infinite distance possess an emergent higher-spin symmetry, generated by an infinite tower of currents whose anomalous dimensions vanish exponentially in the distance. Our conjectures are related to the Distance Conjecture in the swampland program. We discuss the supporting evidence, their holographic interpretation, and implications for superconformal field theories.

08.04.2021 (Thursday)

Moduli space of vortices and 3d supersymmetric gauge theories

Regular Seminar Heeyeon Kim (Rutgers)

at:
14:00 QMW
room zoom
abstract:

[For zoom link please email s.nagyATqmul.ac.uk There will be a pre-seminar for students at 13:30] I will discuss the geometric interpretation of the twisted index of 3d supersymmetric gauge theories on a closed Riemann surface. I will show that the twisted index reproduces the virtual Euler characteristic of the moduli space of solutions to vortex equations on the Riemann surface. I will also discuss 3d N = 4 mirror symmetry in this context, which implies non-trivial relations between enumerative invariants associated to the moduli space of vortices. Finally, I will comment on level structures and a wall-crossing formula of the twisted indices derived from the gauge theory point of view.

01.04.2021 (Thursday)

Scrambling in Yang-Mills

Regular Seminar Robert de Mello Koch (Witwatersrand U.)

at:
14:00 QMW
room zoom
abstract:

We study operators with a bare dimension that grows as N^2 in the large N limit. These operators are labeled by a Young diagram with p long rows, as well as a graph, with p nodes. The dilatation operator describing the mixing of these operators defines a Hamiltonian for excitations hopping on this graph. The scrambling and equilibration of the resulting dynamics is studied. [For zoom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

25.03.2021 (Thursday)

Another dimension of Kerr

Regular Seminar Donal O'Connell (Edinburgh U.)

at:
14:00 QMW
room zoom
abstract:

[there will be a 30min pre-seminar for students. For zoom link, please contact s.nagyATqmul.ac.uk] Abstract: Recent work has broadened the scope of scattering amplitudes to include large, classical objects such as the Kerr black hole. This new perspective illuminates surprising aspects of classical gravity, such as the Newman-Janis shift relating Kerr to Schwarzschild. I will describe the connection between amplitudes and classical physics, focussing on the case of Kerr.

11.03.2021 (Thursday)

QCD instantons and Hadron Colliders

Regular Seminar Valentin Khoze (Durham U.)

at:
14:00 QMW
room zoom
abstract:

QCD instantons are arguably the best motivated yet unobserved nonperturbative effects predicted by the Standard Model. A discovery and detailed study of instanton-generated processes at colliders would provide a new window into the phenomenological exploration of QCD and a vastly improved fundamental understanding of its non-perturbative dynamics. We present for the first time a full calculation of QCD instanton-induced processes in proton-proton collisions accounting for quantum corrections due to both initial and final state gluon interactions. Although QCD instanton processes are predicted to be produced with a large scattering cross-section at small centre-of-mass partonic energies, discovering them at hadron colliders is a challenging task that requires dedicated search strategies. [Based on https://arxiv.org/abs/2010.02287 and https://arxiv.org/abs/1911.09726.] [for zoom link contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

25.02.2021 (Thursday)

Energy correlations at conformal collider

Regular Seminar Gregory Korchemsky (IPhT Saclay)

at:
14:00 QMW
room zoom
abstract:

[For zoom link please contact s.nagyATqmul.ac.uk. There will be a pre-seminar for students at 13:30] The energy-energy correlation (EEC) measures the angular distribution of the energy that flows through two calorimeters separated by some relative angle in the final state created by a source. We present a new approach to computing this observable that exploits the relation between the energy correlations and four-point correlation functions of conserved currents. In the limit of small and large angles, when EEC describes the correlation between particles belonging, respectively, to the same jet and to two almost back-to-back jets, we obtain a concise representation of the EEC in terms of the conformal data of twist-two operators and verify it by comparing with the results of explicit calculation at next-to-next-to-leading order in maximally supersymmetric Yang-Mills theory. As a byproduct of our analysis, we predict the maximal weight part of the analogous QCD expression.

18.02.2021 (Thursday)

OPE for form factors

Regular Seminar Amit Sever (Tel Aviv U.)

at:
16:00 QMW
room zoom
abstract:

We propose an operator product expansion for planar form factors of local operators in N = 4 SYM theory. This expansion is based on the dual conformal symmetry of these objects or, equivalently, the conformal symmetry of their dual description in terms of periodic Wilson loops. A form factor is decomposed into a sequence of known pentagon transitions and a new universal object that we call the “form factor transition”. This transition is subject to a set of non-trivial bootstrap constraints, which allows us to bootstrap it at any value of the coupling. We evaluate the form factor transition for MHV form factors of the chiral half of the stress tensor supermultiplet at leading order in perturbation theory and use it to produce OPE predictions at any loop order. We match the one-loop and two-loop predictions with data available in the literature. [for zoom link contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

11.02.2021 (Thursday)

Knot Theory and Machine Learning

Regular Seminar Fabian Ruhle (CERN)

at:
14:00 QMW
room Zoom
abstract:

[For zoom details please email s.nagyATqmul.ac.uk There will be a pre-seminar for students at 13:30] Knot theory plays an important role in physics, mathematics and biology. Characterizing knots is, however, a difficult task. There are different ways to represent a knot (e.g. via braids, Gauss codes, Dowker-Thistlethwaite notation), and many knot invariants exist (e.g. the Alexander polynomial, Jones polynomial, determinant, slice genus). However, it is not known whether these can be used to identify a trivial knot, the so-called unknot. We use different machine learning techniques to tackle this question. First, we use a very recent neural network architecture developed for natural language processing, called the reformer, to decide whether a given knot is the unknot. We also apply Reinforcement Learning to solve the harder problem of finding a set of Reidemeister/Markov moves that explicitly simplify a given knot as much as possible. If the algorithm finds a sequence of moves that removes all crossings of a knot in a given representation, then this knot is provably the unknot.

03.02.2021 (Wednesday)

Quantum Information Theory of the Gravitational Anomaly

Triangular Seminar Simeon Hellerman (Tokyo U., IPMU)

at:
15:00 QMW
room Zoom
abstract:

I will explain that the notion of quantum entanglement is not defined for gravitationally anomalous two-dimensional theories, because they do not admit a local tensor factorization of the Hilbert space into local Hilbert spaces. Qualitatively, the modular flow cannot act consistently and unitarily in a finite region, if there are different numbers of states with a given energy traveling in the two opposite directions. I will make this precise by decomposing it into two observations: First, a two-dimensional conformal field theory admits a consistent quantization on a space with boundary only if it is not anomalous. Second, a local tensor factorization always leads to a definition of consistent, unitary, energy-preserving boundary condition. As a corollary I will establish a generalization of the Nielsen-Ninomiya theorem to all two-dimensional unitary local quantum field theories: No continuum quantum field theory in two dimensions can admit a lattice regulator unless its gravitational anomaly vanishes. I will advocate that these points be used to reinterpret the gravitational anomaly quantum-information-theoretically, as a fundamental obstruction to the localization of quantum information. [Zoom link: please ask your local triangle organizer]

03.02.2021 (Wednesday)

Islands in black holes and cosmology

Triangular Seminar Tom Hartman (Cornell)

at:
16:30 QMW
room Zoom
abstract:

I will summarize recent developments on the information paradox involving "islands" and replica wormholes, and discuss the extent to which these ideas can be applied to cosmology. [Zoom link: please ask your local triangle organizer]