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)

16.01.2020 (Thursday)

Exact structure constants of determinant operators

Regular Seminar Edoardo Vescovi (Imperial College London)

at:
14:00 QMW
room G O Jones 610
abstract:

In this talk, based on [1906.07733] and [1907.11242] with Y. Jiang and S. Komatsu, we derive the first non-perturbative result for the structure constant of two determinant operators and a non-BPS single-trace operator of finite length in planar N=4 SYM. First, we introduce an effective theory for such correlators at zero coupling. The form of the result supports the interpretation of the three-point function as an overlap between an integrable boundary state, which we determine using symmetry and integrability, and the state describing the single-trace operator. Second, we use thermodynamic Bethe ansatz to derive a non-perturbative expression for such overlap. Finally, we discuss applications that could be addressed with these methods.

09.01.2020 (Thursday)

Impossible Theories of Gravity

Regular Seminar Brando Bellazzini (IPHT)

at:
14:00 QMW
room G O Jones 610
abstract:

Not every effective theory of fields and gravitational interactions at low energy can be embedded into a consistent theory of gravity at short distances. I will discuss how fundamental properties of scattering amplitudes, such as unitarity and causality of the underlying fundamental theory, can be used to spot inconsistent theories of gravity at low-energy, and hence throw them in the so-called EFT ``swampland'’. I will focus on two main applications: the weak gravity conjecture for the physics of extremal black holes; and modified gravity theories such as Galileons, of interest for late-time cosmology.

12.12.2019 (Thursday)

The Speed of Gravity

Regular Seminar Claudia de Rham (Imperial College London)

at:
14:00 QMW
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.

11.12.2019 (Wednesday)

Generalised Quotients

Exceptional Seminar Falk Hassler (University of Oviedo)

at:
14:00 QMW
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.

09.12.2019 (Monday)

Solving M-theory with the Conformal Bootstrap and Localization

Exceptional Seminar Shai Chester (Weizmann Institute of Science)

at:
14:30 QMW
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.

05.12.2019 (Thursday)

Logarthmic vs rational conformal field theory -- Who really wants to be rational anyway?

Regular Seminar Simon Wood (Cardiff University)

at:
14:00 QMW
room G O Jones 610
abstract:

Two-dimensional conformally invariant quantum field theories (CFTs for short) form a sprawling network of ideas connecting many areas of physics and mathematics. A particularly celebrated class are the rational CFTs. These are essentially characterised by having a completely reducible representation theory and only a finite number of inequivalent irreducible representations. Rational CFTs exhibit a number of extraordinary features, foremost being the Verlinde formula which determines correlation functions from certain transformation properties of the CFTs characters. Logarithmic CFTs by contrast are almost maximally awful in that their representation theory is necessarily not completely reducible and need not have finitely many inequivalent irreducible representations. I will present recent results on such logarithmic CFTs and argue that suitable generalisations of rational features exist, at least in certain cases. So things are not as bad as one might fear.

28.11.2019 (Thursday)

Cluster Adjacency, Tropical Geometry, and Scattering Amplitudes

Regular Seminar Jack Foster (University of Southampton)

at:
14:00 QMW
room G O Jones 610
abstract:

I will discuss two new areas of interest in scattering amplitudes: cluster adjacency and tropical geometry. The former describes how the analytic structure of planar amplitudes in N=4 Super Yang-Mills is controlled by mathematical objects called cluster algebras. The latter has been used to calculate amplitudes in the biadjoint phi^3 theory, which I will discuss briefly, but it also has implications for cluster adjacency.

21.11.2019 (Thursday)

Conformal symmetry in strong interactions

Regular Seminar Vladimir Braun (Universitaet Regensburg)

at:
14:00 QMW
room G O Jones 610
abstract:

Description:I will give a review of recent applications of conformal symmetry to perturbative calculations in Quantum Chromodynamics (QCD) by nexploiting the connection of physical theory to QCD at non-intege number of space-time dimensions at the critical point.

14.11.2019 (Thursday)

Parton branching at amplitude level

Regular Seminar Jack Holguin (University of Manchester)

at:
14:00 QMW
room G O Jones 610
abstract:

TeV hadron colliders provide the backbone for modern day particle physics. As a consequence, understanding QCD radiation is a vital step in linking theory with experiment. Over the last few decades a semi-classical treatment of radiation has been hugely successful; particularly the treatment given by Monte-Carlo event generators. However, as experiments demand greater precession, the traditional approaches struggle to keep up. Recently focus has been given to fully quantum approaches to QCD radiation by working directly with amplitudes rather than semi-classical probabilities. In my talk I will give an introduction to the current semi-classical approaches and where they fail. I'll then discuss some of the amplitude level techniques that are being developed. The amplitude techniques have broad application. I will give a case study of how these techniques can be used to elucidate coherence violation in QCD.

07.11.2019 (Thursday)

Gravity at high loops

Exceptional Seminar Zvi Bern (UCLA)

at:
14:00 QMW
room PP1
abstract:

07.11.2019 (Thursday)

07.11.2019 (Thursday)

Amplitudes in search of gravitational waves

Exceptional Seminar David Kosower (CEA Saclay)

at:
16:30 QMW
room PP1
abstract:

24.10.2019 (Thursday)

Differential equations for one-loop string integrals

Regular Seminar Oliver Schlotterer (Uppsala University)

at:
14:00 QMW
room G O Jones 610
abstract:

In this talk, I will describe new mathematical structures in the low-energy expansion of one-loop string amplitudes. The insertion of external states on the open- and closed-string worldsheets requires integration over punctures on a cylinder boundary and a torus, respectively. Suitable bases of such integrals will be shown to obey simple first-order differential equations in the modular parameter of the surface. These differential equations will be exploited to perform the integrals order by order in the inverse string tension, similar to modern strategies for dimensionally regulated Feynman integrals. Our method manifests the appearance of iterated integrals over holomorphic Eisenstein series in the low-energy expansion. Moreover, infinite families of Laplace equations can be generated for the modular forms in closed-string low-energy expansions.

23.10.2019 (Wednesday)

Anomalous supersymmetry

Polygon Seminar Kostas Skenderis (University of Southampton)

at:
15:00 QMW
room Bancroft 2.40
abstract:

I will present an introduction to anomalies and then discuss the recently discovered anomalies for supersymmetry.

17.10.2019 (Thursday)

Amplitudes in Strong Field Yang-Mills

Regular Seminar Tim Adamo (Edinburgh)

at:
14:00 QMW
room G O Jones 610
abstract:

Usually, scattering amplitudes in quantum field theory are computed perturbatively around a trivial background, but there are many reasons to be interested in non-trivial (or 'strong') background fields. These range from laser physics and QCD processes near heavy ion collisions to gravitational waves, conformal field theories and cosmology. Strong backgrounds also give us a way to test the robustness of new structures which have been discovered in scattering amplitudes. I will discuss perturbative Yang-Mills theory on a particularly simple (but important) background known as a plane wave, and consider a very basic observable: the scattering amplitude for a gluon to flip helicity as it crosses the background. This 'helicity flip' amplitude is a loop effect, and the leading result for Yang-Mills (and QCD) can be expressed compactly using a background-dressed version of the spinor helicity formalism (a method for freely specifying on-shell kinematics). Time permitting, I may also make some remarks about higher-point gluon amplitudes in the plane wave background, or the version of this story for gravity.

10.10.2019 (Thursday)

Non-relativistic gravity and strings

Regular Seminar Niels Obers (Nordita)

at:
14:00 QMW
room G O Jones 610
abstract:

I will start by motivating the recent interest in non-relativistic gravity and strings, and introduce the basics of Newton-Cartan geometry. Newton-Cartan (NC) geometry was introduced more than 90 years ago in order to find a geometric formulation of Newtonian gravity. This geometry (including recent novel generalisation and extensions) has gained renewed interest as it appears in a variety of settings in modern theory involving gravity, string theory and holography. I will then talk about recent work on an action principle for non-relativistic gravity, including its Newtonian limit. This requires a new notion of NC geometry, which naturally arises in a covariant 1/c expansion of general relativity, with c being the speed of light. The corresponding non-relativistic truncation of general relativity goes beyond Newtonian gravity and is able to correctly describe gravitational time dilation. Finally, I will discuss the relevance and appearance of non-relativistic geometry in connection to non-relativistric string theory and holography.

03.10.2019 (Thursday)

Finite temperatures and modular forms

Regular Seminar David McGady (NBI)

at:
14:00 QMW
room G O Jones 610
abstract:

Temperature manifests itself within quantum field theories (QFTs) and conformal field theories (CFTs) via an identification of points in the Euclidean-time direction, which differ by an integer multiple of 1/T. Today, I will talk about finite-temperature path integrals for general QFTs and for two-dimensional CFTs (2d CFTs) on the compact two-torus. By definition, the latter path integrals are modular invariant. I will discuss why, propose an extension of the modular group from SL_2(\Z) to GL_2(\Z), introduce the notion of modular forms with poles, and discuss general properties of modular forms with and without poles that are defined on the extended group GL_2(\Z). Finally, I will discuss how this extension to GL_2(\Z) may introduce a new source of anomalies/consistency conditions in 2d CFTs (and beyond).

30.09.2019 (Monday)

Conformal Bootstrap and Continuous Phase Transitions in 3D

Exceptional Seminar Andreas Stergiou (LANL)

at:
14:00 QMW
room G.O. Jones 610
abstract:

Renormalization group methods have been used for almost 50 years to obtain results for critical exponents of conformal field theories (CFTs), while relying on assumptions and approximations that are not rigorously justified. More recently, the numerical conformal bootstrap, a fully nonperturbative method, has proven to be very powerful in calculating critical exponents and other physical observables of unitary CFTs. In this talk we will review the numerical conformal bootstrap method and discuss its applications to 3D CFTs relevant for continuous phase transitions observed in various experiments.

18.09.2019 (Wednesday)

String corrections to AdS amplitudes and the double-trace spectrum of N = 4 SYM

Informal Seminar Dhritiman Nandan (University of Southampton)

at:
15:30 QMW
room 610
abstract:

We consider α′ corrections to four-point correlators of half-BPS operators in N = 4 super Yang-Mills theory in the supergravity limit within the context of AdS/CFT. By demanding the correct behaviour in the flat space limit, we find that the leading (α′)^3 correction to the Mellin amplitude is fixed for arbitrary charges of the external operators. We consider double-trace operators and observe striking patterns in the α′ corrections to the spectra which hint at their common ten-dimensional origin. By extending the observed patterns and imposing them at order (α′)^5 we are able to reproduce recent results for certain correlators as well as deduce some new results.

14.08.2019 (Wednesday)

Traversable wormholes in four dimensions

Journal Club Iva Lovrekovic (Imperial College)

at:
14:00 QMW
room 610
abstract:

I will talk about the recent quite interesting article by Maldacena, in which he writes on the subject of the traversable wormholes. The most interesting thing that needs to be pointed out here are the way that wormholes are stabilised without the addition of the exotic matter while the theory that describes them is still Einstein gravity, with Maxwell theory and charged massless fermion, since wormholes without the addition of the exotic matter have been known in the higher derivative theories. The wormhole is made possible by fermions that give rise to negative Casimir-like energy and by being a long wormhole which does not lead to causality violations. https://arxiv.org/abs/1807.04726