Found 15 result(s)

### 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.

### 06.10.2016 (Thursday)

#### Geometry = Efficiency? Decoding the DNA of Prediction

Regular Seminar John Joseph Carrasco (CEA)

 at: 14:00 QMWroom G.O. Jones 610 abstract: One can easily be frustrated by the tremendous redundancy in possible physical description. By this I mean the freedom to choose gauge, make field redefinitions, add any amount of auxiliary spectator matter, and the such. Happily we can exploit such freedom to encourage the emergence of a new duality in gauge theories. The existence of a duality between color and kinematics exposes a hidden local double-copy structure inherent to prediction in many theories. This structure weaves its way between theories both formal and phenomenological, from QCD to Gravity, from Chiral Perturbation Theory to Born-Infeld and Volkov-Akulov, and from open to closed superstring theories. The duality is sharpest at the level of the perturbative S-matrix — so I will focus my talk there, although I will also mention some recent provocative work beyond scattering. I will mainly discuss progress and challenges to generically achieving color-dual kinematic representations at the multi-loop level. I present a path forward that introduces, at least temporarily, a redundancy of description that we can exploit to map a set of functional relations to linear ones. I will talk about this approach in terms of a geometric picture involving the graph of local graphs, discussing tradeoffs and applicability to long-standing problems.

### 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.

### 11.11.2014 (Tuesday)

#### String Compactifications, Dark Radiation and a 0.1-1 keV Cosmic Axion Background

Regular Seminar Joseph Conlon (Oxford U., Theor. Phys.)

 at: 13:30 ICroom H503 abstract:

### 09.10.2014 (Thursday)

#### Tensor Models and Renormalization

Regular Seminar Joseph Ben Geloun (AEI Golm)

 at: 14:00 QMWroom G.O. Jones 610 abstract: A review will be provided on the renormalization program for the so-called Tensor Models for Quantum Gravity. These are non local field theories extending both the matrix models, a successful framework in statistical mechanics applied to 2D physics, and the Grosse-Wulkenhaar model in the matrix basis arising in Noncommuting Neometry. We will emphasize the Multi-scale renormalization but also report recent results on the Functional Renormalization Group Approach for these class of models.

### 24.03.2014 (Monday)

#### Lattice Formulations of Supersymmetric Yang-Mills Theories

Informal Seminar Anosh Joseph (DESY)

 at: 15:00 ICroom H503 abstract: Certain classes of supersymmetric Yang-Mills (SYM) theories including the well known N=4 SYM, that takes part in the AdS/CFT correspondence, can be formulated on a Euclidean spacetime lattice using the techniques of exact lattice supersymmetry. In this talk I will provide the constructions of such theories and describe how great ideas such as topological field theories, Dirac-Kahler fermions, geometric discretization all come together to create lattice SYM theories that are exact-supersymmetric, gauge-invariant, local and doubler-free on the lattice. Then I move on to discuss the recent lattice constructions of specific classes SYM theories in two dimensions, with matter in various representations.

### 12.12.2013 (Thursday)

Regular Seminar Jose Edelstein (University of Santiago de Compostela)

 at: 14:00 QMWroom Lecture Theatre abstract: Lovelock theory is the natural extension of general relativity to higher dimensions. It can be also thought of as a toy model for ghost-free higher curvature gravity. It admits a family of AdS vacua, most (but not all) of them supporting black holes, that display interesting features such as a generalized variant of the Hawking-Page phase transition. This provides an appealing arena to explore different holographic aspects in the context of the AdS/CFT correspondence which I will discuss in this talk.

### 29.02.2012 (Wednesday)

#### Brane/Antibrane Backreaction in Axion Monodromy Inflation

Regular Seminar Joseph Conlon (Oxford)

 at: 13:15 KCLroom S4.23 abstract: TransPlanckian inflationary excursions are very interesting because they are sensitive to Planck-suppressed operators and can generate observable tensor modes. I review one proposed model generating a transPlanckian excursion and argue that consideration of antibrane backreaction renders the assumptions entering the model inconsistent.

### 24.01.2012 (Tuesday)

#### Homogeneous supergravity backgrounds

Regular Seminar Jose Figueroa-O'Farrill (Edinburgh)

 at: 13:30 ICroom H503 abstract: We've known since childhood that symmetry can be a very powerful tool in solving partial differential equations. With a little symmetry, one can reduce the number of independent variables, whereas with some more symmetry one can usually separate variables and reduce the problem to solving ordinary differential equations. Given enough symmetry, though, partial differential equations become algebraic. A large body of current research in our field requires finding solutions to the (super)gravity field equations and in this talk I will motivate the search for homogeneous supergravity backgrounds and mention some recent results in this area.

### 12.11.2009 (Thursday)

#### Gauge threshold corrections for local string models

Regular Seminar Joseph Conlon (Oxford)

 at: 13:45 QMWroom 410A abstract: Local string models are those where Standard Model degrees of freedom arise on a small region inside a large bulk volume. I study threshold effects on gauge coupling running for such models. The Kaplunovsky-Louis formula for locally supersymmetric gauge theories predicts the unification scale should be the bulk winding mode scale, parametrically large than the string scale where divergences are naively cut off. Analysis of explicit string models on orbifold/orientifold geometries confirms this. The winding mode scale arises from the presence of tadpoles uncancelled in the local model. I briefly discuss phenomenological applications to supersymmetry breaking and gauge coupling unification.

### 27.02.2008 (Wednesday)

#### Killing superalgebras in supergravity

Triangular Seminar Jose Figueroa-O'Farrill (University of Edinburgh)

 at: 16:00 QMWroom LG1 abstract: I will discuss several constructions of superalgebras associated to the Killing spinors of a supergravity background, with special emphasis on the ten- and eleven-dimensional supergravities.

### 29.01.2008 (Tuesday)

#### Rhombus tilings in representation theory

Regular Seminar Joseph Chuang (City University London)

 at: 17:00 City U.room C322 abstract: I'll introduce a combinatorial problem on tilings of the plane by rhombi and explain how the solution is related to the representation theory of groups.

### 05.10.2005 (Wednesday)

#### Gauged sigma models and generalised geometry

Triangular Seminar Jose Figueroa-O'Farrill (Edinburgh)

 at: 15:00 QMWroom 410 abstract: