Directions

Imperial College has its own detailed information on general directions and on getting to the theoretical physics group. The College is located on Prince Consort Road, south of Hyde Park (map). The most convenient access is via tube (South Kensington, Gloucester Road) or buses. The Theoretical Physics group resides on the 5th floor of the Huxley Building. The group also possesses its own description.

Seminars at Imperial College

Found at least 20 result(s)

21.02.2018 (Wednesday)

Polygon Seminar

Triangular Seminar TBA TBA (TBA)

at:
15:00 IC
room TBA
abstract:

01.11.2017 (Wednesday)

Triangle Seminar

Triangular Seminar TBA TBA (TBA)

at:
15:00 IC
room TBA
abstract:

04.10.2017 (Wednesday)

TBA

Regular Seminar Nabil Iqbal (Durham)

at:
14:00 IC
room H503
abstract:

27.09.2017 (Wednesday)

TBA

Regular Seminar Antoine Bourget (Oviedo)

at:
14:00 IC
room H711C
abstract:

20.09.2017 (Wednesday)

Alternative boundary conditions in AdS, one-loop determinants and WCFTs

Regular Seminar Phil Szepietowski (Utrecht)

at:
14:00 IC
room Elec. Eng. 509A
abstract:

I will discuss the computation of the graviton one-loop determinant in the BTZ black hole background with certain chiral boundary conditions at the AdS boundary. These boundary conditions were proposed by Compere, Song and Strominger and were shown to modify the asymptotic symmetry algebra from a sum of left and right Virasoro algebras to a single right-moving Virasoro U(1) Kac-Moody. This implies that the holographic dual description possesses such global symmetry and so should be described by a warped conformal field theory (WCFT) instead of a standard CFT. In the talk I will overview the new boundary conditions and the concept of a WCFT, outline the computational method of obtaining the one-loop determinant from the "quasinormal" mode spectrum (highlighting elements which are unique to the new boundary conditions) and discuss the implications of the results for the boundary field theory.

14.09.2017 (Thursday)

The decay width of stringy hadrons

Exceptional Seminar Jacob Sonnenschein (Tel Aviv University)

at:
14:00 IC
room H503
abstract:

I will start with briefly describing the HISH ( Holography In- spired Hadronic String) model and reviewing the fits of the spectra of mesons, baryons, glueballs and exotic hadrons. I will present the determination of the hadron strong decay widths. The main decay mechanism is that of a string splitting into two strings. The corresponding total decay width behaves as Γ = πATL/2 where T and L are the tension and length of the string and A is a dimensionless universal constant. The partial width of a given decay mode is given by Γ_i/Γ = Φ_i exp(−2πCm^2_sep/T) where Φi is a phase space factor, msep is the mass of the ”quark” and ”antiquark” created at the splitting point, and C is a dimensionless coefficient close to unity. I will show the fits of the theoretical results to experimental data for mesons and baryons. I will examine both the linearity in L and the expo- nential suppression factor. The linearity was found to agree with the data well for mesons but less for baryons. The extracted coefficient for mesons A = 0.095 ± 0.015 is indeed quite universal. The exponential suppression was applied to both strong and radiative decays. I will discuss the relation with string fragmentation and jet formation. I will extract the quark-diquark structure of baryons from their decays. A stringy mechanism for Zweig sup- pressed decays of quarkonia will be proposed and will be shown to reproduce the decay width of Υ states. The dependence of the width on spin and flavor symmetry will be discussed. We further apply this model to the decays of glueballs and exotic hadrons.

13.09.2017 (Wednesday)

Higher-loop amplitude monodromy relations in string and gauge theory

Regular Seminar Piotr Tourkine (DAMTP)

at:
14:00 IC
room H503
abstract:

The monodromy relations of scattering amplitudes in string theory provide an elegant formalism to understand some mysterious properties of tree-level field theory amplitudes, like the color-kinematics duality. This duality has been instrumental in tremendous progress on the computations of loop-amplitudes in quantum field theory, but a loop-level generalisation of the stringy monodromy construction has been lacking for many years. In this talk I will first describe some of these recent developments in the domain of scattering amplitudes in gauge and gravity theories. I’ll then review the monodromies of open string worldsheets and how the lead at tree-level to deepening the understanding of the gauge theory perturbative expansion. Then I will describe in a non-technical manner our results and how we managed to extend these relations to all loops in string and field theory. I’ll finish by discussing implications for the loop expansion in general, and how to extend in principle these results to gravity. I will assume no prior knowledge of the audience in modern scattering amplitudes methods.

26.05.2017 (Friday)

Goldstino superfields in supergravity

Exceptional Seminar Sergei Kuzenko (U Western Australia)

at:
15:00 IC
room H503
abstract:

Models with spontaneously broken local supersymmetry are naturally obtained by coupling the off-shell supergravity-matter systems to Goldstino superfields. Every irreducible Goldstino superfield produces a universal positive contribution to the cosmological constant. This talk will review the structure of N=1 and N=2 Goldstino superfields.

24.05.2017 (Wednesday)

Diffusion and Chaos in Holographic Matter

Regular Seminar Mike Blake (MIT)

at:
14:00 IC
room H503
abstract:

In this talk I will discuss recent developments that have suggested new connections between the transport properties of strongly interacting matter and the field of quantum chaos. In particular I will describe how in many holographic theories there are simple relationships between the thermoelectric diffusion constants and the butterfly velocity, which describes the speed at which quantum chaos propagates.

22.05.2017 (Monday)

An introduction to Gauge Theory in Superspace

Exceptional Seminar Rikard von Unge (Masaryk University)

at:
14:00 IC
room B1004
abstract:

TBA

18.05.2017 (Thursday)

Double field theory and doubled geometry

Regular Seminar Chris Blair (Vrije U., Brussels)

at:
13:00 IC
room H503
abstract:

I will discuss some aspects of the doubled geometry of double field theory. Double field theory provides a reformulation of supergravity with a manifest O(D,D) symmetry, which can be related to the T-duality invariance of string theory on a torus. I will review how one achieves this, by doubling the number of coordinates and introducing a generalised diffeomorphism symmetry. Then, I will discuss how one can characterise the properties of string theory backgrounds viewed as solutions of DFT, and in particular show how to derive the first law of black hole thermodynamics in this framework. Based mainly on 1507.07541 and 1608.04734 (with Alex Arvanitakis).

10.05.2017 (Wednesday)

M-theory on deformed Sasaki-Einstein manifolds

Regular Seminar Stefanos Katmadas (IPhT, Saclay)

at:
14:00 IC
room H503
abstract:

Compactifications of M-theory down to AdS4 are known to arise from Sasaki-Einstein internal spaces. The latter can be viewed as surfaces enclosing Calabi-Yau cone singularities, whose deformations can be described algebraically in a well established way. In this talk, I will present work in progress on describing deformations of the enclosing surfaces away from the Sasaki-Einstein metric, using the deformations of the Calabi-Yau cone. This provides a realisation of a class of SU(3) structure manifolds satisfying the conditions postulated in the standard treatments of M-theory compactifications on such manifolds. The result is a proposal for obtaining four dimensional N=2 supergravity models with gauged hypermultiplets from deformations of regular Sasaki-Einstein manifolds.

03.05.2017 (Wednesday)

Diffusion and chaos in holographic systems at non-zero density

Regular Seminar Richard Davison (Harvard)

at:
14:00 IC
room H503
abstract:

Recent work has uncovered relations between the rate at which chaotic behaviour spreads in strongly interacting quantum systems, and the diffusivities of certain processes in these systems. Focusing mainly on holographic examples, I will explore the extent to which these relations hold in states at non-zero density, where the diffusion of charge and energy are no longer independent processes.

05.04.2017 (Wednesday)

Supersymmetric microstate geometries

Regular Seminar Harvey Reall (Cambridge)

at:
14:00 IC
room H503
abstract:

A microstate geometry is a smooth, time-independent, asymptotically flat, horizon-free solution of type IIB supergravity. According to the “fuzzball" conjecture, such solutions describe individual microstates of black holes. Non-supersymmetric microstate geometries typically suffer from linearized instabilities. I will argue that supersymmetric microstate geometries suffer from a nonlinear instability. I will also discuss how such solutions lead to a new type of mathematical structure, so-called “ambipolar” hyperkahler manifolds, and explain how such manifolds can be constructed.

29.03.2017 (Wednesday)

Yang-Baxter strings, twists, and AdS/CFT

Regular Seminar Stijn van Tongeren (Humboldt U.)

at:
14:00 IC
room H503
abstract:

The appearance of integrability in the duality between the AdS5xS5 string and planar maximally supersymmetric Yang-Mills theory gives rise to many insightful results. Various deformations of this AdS/CFT dual pair are known to also be integrable, prompting the question how far the power of integrability extends in this setting. In recent years there has been a lot of progress in answering this question. Rather than trying to demonstrate integrability in known AdS/CFT dual pairs, efforts instead focused on finding manifestly integrability preserving deformations of the AdS5xS5 string. While constructed to preserve integrability, the resulting so-called Yang-Baxter sigma models are, however, not guaranteed to describe strings, or have an AdS/CFT interpretation. The former of these points has since been addressed and turns out to be closely related to (nonabelian) T duality, and we now understand which of these models continue to describe strings. The goal of my talk is to address the latter point, regarding the AdS/CFT interpretation of these models. I will use symmetry considerations to give a unified AdS/CFT picture for these Yang-Baxter strings as duals to various noncommutative deformations of supersymmetric Yang-Mills theory. My general conjecture matches many known dualities, and I will briefly discuss nontrivial tests in various new cases, in the form of brane constructions indicating the desired dualities.

23.03.2017 (Thursday)

The a-function in 3 dimensions

Regular Seminar Ian Jack (Liverpool)

at:
13:00 IC
room H503
abstract:

The a-theorem expressing the monotonicity of renormalisation group flows in four (and other even) dimensions is now well-accepted. There is a function (the a-function) generating the RG beta-functions as a gradient flow via a positive-definite metric. However the standard definition of the a-function in terms of the trace anomaly of the energy-momentum tensor does not work in odd dimensions. In this talk we focus on the gradient-flow property of the a-function and show that a function with similar properties can be constructed order-by-order in three dimensions. We start by reviewing the a-function in even dimensions from a gradient-flow standpoint. Then we discuss our explicit calculations in three dimensions. Finally we present some progress towards relating our results to the F-function which has been shown to have the expected monotonicity properties at fixed points.

16.03.2017 (Thursday)

Quantum Geometry and Non-Geometric Backgrounds

Exceptional Seminar Richard Szabo (Heriot-Watt U.)

at:
13:00 IC
room H503
abstract:

Recent advances in non-geometric string theory suggest that locally non-geometric flux compactifications can be understood in terms of nonassociative deformations of spacetime geometry. We will review some of these developments and how they shed light on properties of non-geometric strings, and explain some new results concerning how these structures lift to non-geometric M-theory.

15.03.2017 (Wednesday)

Algebraic properties of the monopole formula

Regular Seminar Marcus Sperling (Vienna U.)

at:
14:00 IC
room H503
abstract:

In this talk, I will discuss how the two geometric notions "fan" and "monoid" can be very fruitful for the understanding of the monopole formula for 3d N=4 gauge theories. After a brief reminder of the monopole formula, I will introduce the matter fan and reorganise the monopole formula accordingly. I then discuss the resulting benefits such as: (1) Explicit expressions for the Hilbert series built from well-studied constituents. (2) Proof that the order of the pole at t=1 and t → ∞ equals the complex or quaternionic dimension of the Coulomb branch. (3) Identification of a sufficient set of chiral ring generators.

08.03.2017 (Wednesday)

Localization of supersymmetric field theories on non-compact hyperbolic three-manifolds

Regular Seminar Daisuke Yokoyama (King's College London)

at:
14:00 IC
room H503
abstract:

I am going to talk about how to derive an exact partition function of supersymmetric field theories on a supersymmetry-preserving quotient of Euclidean AdS_3 by localization. This is one of first examples about localization on non-compact spaces. I will describe the situation by comparing it to a situation in compact spaces. Then, I will explain how to perform a localization procedure on the manifold, and finally, I will discuss the features of the partition function we derived.

22.02.2017 (Wednesday)

Polygon Seminar: E Theory

Triangular Seminar Peter West (King's College London)

at:
15:00 IC
room Huxley 140
abstract:

I review the theory of non-linear realisations and Kac-Moody algebras, I explain how to construct the non-linear realisation based on the Kac-Moody algebra $E_{11}$ and its vector representation. I explain how this field theory leads to dynamical equations which contain an infinite number of fields defined on a spacetime with an infinite number of coordinates. I then show that these unique dynamical equations, when truncated to low level fields and the usual coordinates of spacetime, lead to precisely the equations of motion of eleven dimensional supergravity theory. By taking different group decompositions of $E_{11}$ we find all the maximal supergravity theories, including the gauged maximal supergravities, and as a result the non-linear realisation is a unified theory that is the low energy effective action for type II strings and branes. These results essentially confirm the $E_{11}$ conjecture given many years ago.