Found at least 20 result(s)

### 04.10.2018 (Thursday)

#### tba

Regular Seminar Diego Rodriguez-Gomez (Oviedo U.)

 at: 14:00 QMWroom G O Jones 610 abstract: tba

### 23.07.2018 (Monday)

#### Einstein Double Field Equations

Regular Seminar Jeong-Hyuck Park (Sogang University)

 at: 15:30 QMWroom 410 abstract: String theory predicts its own gravity rather than GR. In General Relativity the metric is the only geometric and gravitational field, whereas in string theory the closed-string massless sector comprises a skew-symmetric B-field and the string dilaton in addition to the metric. Furthermore, these three fields transform into each other under T-duality. This hints at a natural augmentation of GR: upon treating the whole closed string massless sector as stringy graviton fields, Double Field Theory may evolve into Stringy Gravity'. Equipped with an O(D,D) covariant differential geometry beyond Riemann, we spell out the definitions of the stringy Einstein curvature tensor and the stringy Energy-Momentum tensor. Equating them, all the equations of motion of the closed string massless sector are unified into a single expression which we dub the Einstein Double Field Equations.

### 13.03.2018 (Tuesday)

#### tba

Regular Seminar Attila Csikasz-Nagy (KCL)

 at: 15:00 City U.room B103 abstract:

### 27.02.2018 (Tuesday)

#### Topological strings and 6d SCFTs

Regular Seminar Amir-Kian Kashani-Poor (ENS)

 at: 15:00 City U.room B103 abstract: The topological string is a simplified version of physical string theory. It is of interest because it computes the BPS spectrum of relevant string theory compactifications, but also because it shares structural properties of physical string theory, Dualities and symmetries which often must be argued for arduously in the physical string can often be verified by computation in the topological setting. The central observable of the theory is the topological string partition function Z_top. This quantity has an eerie habit of making surprise appearances in many areas of mathematical physics. Numerous techniques exist for its computation in various expansions in parameters of the theory, yet to date, no satisfactory closed form for this quantity is known. In this talk, after reviewing notions of topological string theory with an emphasis on the interplay between worldsheet and target space physics (one of the structural similarities between the physical and the topological string alluded to above), I will report on progress in computing Z_top in settings where it is related to enigmatic 6d theories.

### 04.10.2017 (Wednesday)

#### The topologically twisted index on H2xS1 and its relation to the entropy of hyperbolic AdS4 black holes.

Regular Seminar Alejandro Cabo-Bizet (KCL)

 at: 13:15 KCLroom K4.31 abstract: I will start by sketching the computation of the topologically twisted index on H2xS1 and its evaluation in ABJM theory in the large N limit with k=1. Then after, I will review the key points behind the construction of magnetically charged (hyperbolic) AdS4 black holes on STU gauged SUGRA and will conclude by stating how the aformentioned index -- upon extremization -- coincides with the entropy of the latter black holes in the large N limit (with k=1).

### 05.07.2017 (Wednesday)

#### Holography of BCFT

Regular Seminar Chong-Sun Chu (NCTS, Hsinchu and Taiwan, Natl. Tsing Hua U.)

 at: 11:30 QMWroom 610 abstract: In this talk, I will discuss about the holography of boundary Conformal Field theory. I will show how boundary Weyl Anomaly can be obtained from holography. New universal relations between the shape dependence of Casimir effects and boundary Weyl anomaly will also be pointed out and discussed from the point of view of holography.

### 09.11.2016 (Wednesday)

#### An algebraic approach to the classification of supergravity backgrounds

Regular Seminar Jose Miguel Figueroa-O'Farrill (Edinburgh)

 at: 13:15 KCLroom G01 Norfolk Building abstract: I will report on joint work with Andrea Santi outlining an algebraic reformulation of the classification problem of eleven-dimensional supergravity backgrounds. The basic object of study is the Killing superalgebra of the background, whose algebraic structure has recently been elucidated. If time permits I will also comment on work also involving Paul de Medeiros applying these techniques to the construction of rigidly supersymmetric theories in curved spaces.

### 29.08.2016 (Monday)

#### STiL 2016: Supersymmetry, Geometry, and Holography

Exceptional Seminar - - (-)

 at: 10:00 KCLroom tba abstract: 29 August - 3 September, King's College London. This workshop intends to bring together leading experts and young researchers working on the broad themes of quantum field theory, black holes and gravitation, and holography, so as to share new ideas, calculations, and results in a focused setting. The topics covered in the workshop include: Symmetries and dualities in field theory and gravity Classical and quantum aspects of black holes Supersymmetric localization and exact results Mathematical aspects of string theory Supergravity solutions and holography Website Registration will be closed on 8 July 2016 or when positions are filled.

### 17.02.2016 (Wednesday)

#### Brane Brick Models, Toric Calabi-Yau 4-folds and 2d (0,2) Quivers

Exceptional Seminar Rak-Kyeong Seong (KIAS)

 at: 15:30 KCLroom K6.63 abstract: In this talk, I will discuss Type IIA brane configurations consisting of D4-branes suspended between NS5-branes which represent a large class of 2d (0,2) quiver gauge theories. We call these new constructions Brane Brick models. These are T-dual to D1-branes over singular toric Calabi-Yau 4-folds and encode information about the probed Calabi-Yau geometry as well as the corresponding GLSM. If time permits, I will present how Brane Brick models naturally realise in terms of a brane configuration 2d (0,2) Gadde-Gukov-Putrov triality.

### 16.02.2016 (Tuesday)

#### Yang-Mills Theory and the ABC Conjecture

Regular Seminar Yang-Hui He (City)

 at: 15:00 City U.room B103 abstract: We establish a precise correspondence between the ABC Conjecture and N=4 super-Yang-Mills theory. This is achieved by combining three ingredients: (i) Elkies' method of mapping ABC-triples to elliptic curves in his demonstration that ABC implies Mordell/Faltings; (ii) an explicit pair of elliptic curve and associated Belyi map given by Khadjavi-Scharaschkin; and (iii) the fact that the bipartite brane-tiling/dimer model for a gauge theory with toric moduli space is a particular dessin d'enfant in the sense of Grothendieck. We explore this correspondence for the highest quality ABC-triples as well as large samples of random triples. The Conjecture itself is mapped to a statement about the fundamental domain of the toroidal compactification of the string realization of N=4 SYM.

### 26.11.2015 (Thursday)

Regular Seminar Yang-Hui He (City)

 at: 14:00 QMWroom G.O. Jones 610 abstract: We study the web of correspondences linking the exceptional Lie algebras E8,7,6 and the sporadic simple groups Monster, Baby and the largest Fischer group. We will survey some old observations from the perspective of Moonshine and representation theory and present some new ones from that of congruence groups and enumerative geometry. Based on joint work with John McKay.

### 19.11.2015 (Thursday)

#### 5d theories on curved backgrounds, Yang-Mills deformations and instantons

Regular Seminar Diego Rodriguez-Gomez (Universidad de Oviedo)

 at: 14:00 QMWroom G.O. Jones 610 abstract: 5d theories can be at fixed points, in many cases exhibiting rather amusing properties. In this talk we will study several properties of these fixed point theories. In particular, we will describe how to put them supersymmetrically in curved spaces. As a consequence, we will discuss when a deformation to a Yang-Mills theory is possible. The latter typically exhibit a smaller global symmetry that that of the fixed point theory, which, from the YM point of view, appears as an enhanced symmetry. In this enhancement instantons play a pivotal role, and we will discuss several aspects of these.

### 18.11.2015 (Wednesday)

#### Polygon Seminar: An introduction to the Hilbert series as operator counting

Triangular Seminar Diego Rodriguez-Gomez (University of Oviedo)

 at: 15:00 QMWroom GO Jones 610 abstract: Counting operators in supersymmetric field theories is very interesting, as the corresponding generating functions encode properties of the field theory. In this lecture we will mostly concentrate on 4d SUSY field theories. After reviewing some basic notions about SUSY field theories leading to the notion of chiral ring, we will introduce a generating function enumerating operators in the ring. This function is the so-called Hilbert series. In the case of SCFTs with a gravity dual, we will show how this function recovers geometric properties of the dual gravity background. The uses of the Hilbert series go beyond this, since, as we will see, being a counting of operators, it is of relevance in the computation of instanton partition functions for pure gauge theories. In the second part of the lecture we will briefly touch upon these issues.

### 08.10.2015 (Thursday)

#### All gaugings and stable de Sitter in D=7 half-maximal supergravity

Regular Seminar Jose Fernandez-Melgarejo (Harvard)

 at: 13:30 ICroom H503 abstract: We study the general formulation of gauged supergravity in seven dimensions with sixteen supercharges keeping duality covariance by means of the embedding tensor formalism. We first classify all inequivalent duality orbits of consistent deformations. Secondly, we analyse the complete set of critical points in a systematic way. Interestingly, we find the first examples of stable de Sitter solutions within a theory with such a large amount of supersymmetry.

### 30.04.2015 (Thursday)

#### Hidden symmetries of scattering amplitudes (and of Hydrogen atom)

Regular Seminar Simon Caron-Huot (NBI)

 at: 14:00 QMWroom G.O. Jones 610 abstract: Physical systems with unexpected, or hidden,’ symmetries have often played an important role in physics, beginning with the classical Kepler problem whose Laplace-Runge-Lenz vector ensures the closure of planetary orbits, and degeneracies of the Hydrogen spectrum. I will describe how precisely the same symmetry governs a unique four-dimensional quantum field theory, a maximally supersymmetric (`N=4') cousin of the strong-interaction Yang-Mills theory. After reviewing progress in recent years in using these symmetries to solve this model, I will describe novel applications involving massive particles. Combining the Laplace-Runge-Lenz vector with relativity then yields a novel way to calculate the spectrum of its Hydrogen-like bound states, including relativistic corrections. Based on 1408.0296.

### 10.12.2014 (Wednesday)

#### Eta Products, BPS States and K3 Surfaces

Regular Seminar Yang-Hui He (City University)

 at: 13:15 KCLroom G.01 abstract: Inspired by the multiplicative nature of the Ramanujan modular discriminant, Delta, we consider physical realizations of certain multiplicative products over the Dedekind eta-function in two parallel directions: the generating function of BPS states in certain heterotic orbifolds and elliptic K3 surfaces associated to congruence subgroups of the modular group. We show that they are, after string duality to type II, the same K3 surfaces admitting Nikulin automorphisms. In due course, we will present some identities arising from q-expansions as well as relations to the sporadic Mathieu group M24.

### 03.12.2014 (Wednesday)

#### Polygon Seminar: Gauge Theories and Calabi-Yau Manifolds

Triangular Seminar Yang-Hui He (City University)

 at: 15:30 QMWroom Francis Bancroft 1.15 abstract:

### 05.11.2014 (Wednesday)

#### Gerbes on the Lattice

Regular Seminar Ron Reid-Edwards (Hull)

 at: 14:00 ICroom H503 abstract: Abelian gerbes play a ubiquitous role in string and supergravity theories. It is conjectured that non-abelian gerbe theories exist, but a satisfactory explicit construction of such a theory has not yet been achieved. Inspired by the possibility that a non-abelian theory of gerbes may be possible on non-conventional spacetimes, I will consider a toy model on a lattice that allows one to make some progress in this problem. In this talk, I will show how abelian gerbe theories may be described naturally on the lattice. I will outline a non-abelian generalisation and show how, under dimensional reduction, such theories give rise to lattice Yang-Mills.

### 21.03.2014 (Friday)

#### TBA

Regular Seminar Yang-Hui He (City U.)

 at: 14:00 QMWroom Room FB 1.06 abstract:

### 27.02.2014 (Thursday)

#### Aspects of 5d gauge theories

Regular Seminar Diego Rodriguez-Gomez (Oviedo U.)

 at: 14:00 QMWroom G.O. Jones 208 abstract: In this talk I will review recent progress in understanding aspects of 5d gauge theories. Under certain circumstances these can be at fixed points admitting a large N limit, whose gravity dual we will discuss. Such gravity dual suggests a yet more general class of quiver-type fixed point theories which can sometimes be understood in terms of S-duality. To this matter the braneweb construction of the theories will prove very helpful, yielding new insights which we will test using the 5d superconformal index.