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SEMINARS 2013 ​

SEMINAR

 

12/04/13

 

Speaker: Alejandro Rosabal

 

Extended geometry and gauged maximal supergravity

G. Aldazabal, M. Graña, D. Marqués, J. A. Rosabal

 

We consider generalized diffeomorphisms on an extended mega-space associated to the U-duality group of gauged maximal supergravity in four dimensions, E_7. Through the bein for the extended metric we derive dynamical (field-dependent) fluxes taking values in the representations allowed by supersymmetry, and obtain their quadratic constraints from gauge consistency conditions. A covariant generalized Ricci tensor is introduced, defined in terms of a connection for the generalized diffeomorphisms. We show that for any torsionless and metric-compatible generalized connection...

 

http://arxiv.org/abs/arXiv:1302.5419

JOURNAL CLUB

 

12/04/13

 

Speaker: Carmen Nuñez

 

Duality Rotations in String Theory

M.J. Duff

 

&

 

Duality symmetric closed string theory and interacting chiral scalars

Arkady A. Tseytlin

 

 

http://www.sciencedirect.com/science/article/pii/055032139090520N

 

http://www.sciencedirect.com/science/article/pii/055032139190266Z

JOURNAL CLUB

 

24/05/13

 

Speaker: Diego Marques

 

Comments on double field theory and diffeomorphisms

Jeong-Hyuck Park

 

 

As the theory is subject to a section condition, coordinates in double field theory do not represent physical points in an injective manner. We argue that a physical point should be rather one-to-one identified with a `gauge orbit' in the coordinate space. The diffeomorphism symmetry then implies an invariance under arbitrary reparametrizations of the gauge orbits. Within this generalized sense of diffeomorphism, we show that a recently proposed tensorial transformation rule for finite coordinate transformations is actually (i) consistent with the standard exponential map...

 

http://arxiv.org/abs/arXiv:1304.5946

JOURNAL CLUB

 

29/05/13

 

Speaker: Oscar Bedoya

 

Two vierbein formalism for string inspired axionic gravity

W. Siegel

 

 

Using independent left and right vierbeins to describe graviton plus axion as suggested by string mechanics, O(d,d) duality can be realized linearly.

 

http://arxiv.org/abs/hep-th/9302036

JOURNAL CLUB

 

25/06/13

 

Speaker: Carmen Nuñez

 

T-duality of the Riemann curvature corrections to supergravity

Mohammad R. Garousi

 

 

We examine the known Riemann curvature corrections to the supergravity action at order α′3 under the T-duality transformations. Using the compatibility of the action with the linear T-duality and with the S-matrix calculations as guiding principles, we have found the couplings of four B-field strengths and the couplings of two Riemann curvatures and two B-field strengths at order α′3. Using the S-matrix calculations we have also found new dilaton couplings in the string frame at this order.

 

http://arxiv.org/abs/arXiv:1208.4459

JOURNAL CLUB

 

08/08/13

 

Speaker: Victor Penas

 

Gauge theory of Kaluza-Klein and winding modes

Olaf Hohm, Henning Samtleben

 

 

We perform a Kaluza-Klein inspired rewriting of double field theory by splitting the coordinates into `compact' and `non-compact' directions. There is no truncation of the compact coordinates or their duals, and so this formulation is manifestly O(d,d) invariant, with d the number of compact directions. The action can serve as starting point for arbitrary Kaluza-Klein ansaetze. For a torus background the theory describes the full tower of Kaluza-Klein modes or, in the dual frame, of the winding modes.iton plus axion as suggested by string mechanics, O(d,d) duality can be realized linearly...

 

http://arxiv.org/abs/arXiv:1307.0039

JOURNAL CLUB

 

15/08/13

 

Speaker: Oscar Bedoya

 

Doubled α'-Geometry

O. Hohm, W. Siegel and B. Zwiebach

 

We develop doubled-coordinate field theory to determine the \alpha' corrections to the massless sector of oriented bosonic closed string theory. Our key tool is a string current algebra of free left-handed bosons that makes O(D,D) T-duality manifest. While T-dualities are unchanged, diffeomorphisms and b-field gauge transformations receive corrections, with a gauge algebra given by an \alpha'-deformation of the duality-covariantized Courant bracket...

 

http://arxiv.org/abs/arXiv:1306.2970

JOURNAL CLUB

 

21/08/13

 

Speaker: Diego Marques

 

Exceptional Form of D=11 Supergravity

Olaf Hohm, Henning Samtleben

 

Eleven-dimensional supergravity reveals large exceptional symmetries upon reduction, in accordance with the U-duality groups of M-theory, but their higher-dimensional geometric origin has remained a mystery. In this letter, we show that D=11 supergravity can be extended to be fully covariant under the exceptional groups E_{n(n)}, n=6,7,8. Motivated by a similar formulation of double field theory we introduce an extended `exceptional spacetime'...

 

http://arxiv.org/abs/arXiv:1308.1673

JOURNAL CLUB

 

22/08/13

 

Speaker: Victor Penas

 

Covariant action for a string in doubled yet gauged spacetime

Kanghoon Lee, Jeong-Hyuck Park

 

The section condition in double field theory has been shown to imply that a physical point should be one-to-one identified with a gauge orbit in the doubled coordinate space. Here we show the converse is also true and continue to explore the idea of `spacetime being doubled yet gauged'. Introducing an appropriate gauge connection, we construct a string action, with an arbitrary generalized metric, which is completely covariant with respect to the coordinate gauge symmetry, generalized diffeomorphisms, world-sheet diffeomorphisms and O(D,D) T-duality...

 

http://arxiv.org/abs/arXiv:1307.8377

JOURNAL CLUB

 

04/09/13

 

Speaker: Victor Penas

 

The Spacetime of Double Field Theory: Review, Remarks, and Outlook

Olaf Hohm, Dieter Lust, Barton Zwiebach

 

We review double field theory (DFT) with emphasis on the doubled spacetime and its generalized coordinate transformations, which unify diffeomorphisms and b-field gauge transformations. We illustrate how the composition of generalized coordinate transformations fails to associate. Moreover, in dimensional reduction, the O(d,d) T-duality transformations of fields can be obtained as generalized diffeomorphisms. Restricted to a half-dimensional subspace, DFT includes `generalized geometry', but is more general...

 

http://arxiv.org/abs/arXiv:1309.2977

SEMINAR

 

28/09/13

 

Speaker: Mariana Graña

 

Alpha-prime corrections for manifolds with SU(3)-structure

 

JOURNAL CLUB

 

16/10/13

 

Speaker: Carmen Nuñez

 

Duality completion of higher derivative corrections

Hadi Godazgar, Mahdi Godazgar

 

We present a new method for completing higher derivative corrections for theories that exhibit duality symmetries under reduction. This proposal is based on the observation that duality symmetry in the reduced theory highly constrains the form of the unreduced theory. We apply this idea to closed bosonic string theory and complete the Riemann squared term to simply derive the known full tree-level effective action to order alpha'.

 

http://arxiv.org/abs/arXiv:1306.4918

 

SEMINAR

 

13/11/13

 

Speaker: Juan Martin Maldacena

 

Geometría y entrelazamiento

 

 

En teorias cuanticas con duales gravitatorios, la entropia de entrelazamiento puede ser calculada a traves de la geometria asociada. Es posible tener espacio-tiempos que conectan dos regiones asimptoticas. En estos casos la estructura del espacio tiempo parece estar directamente relacionada con el entrelazamiento presente en el estado cuantico de dos sistemas que no interactuan directamente. Esto tiene consecuencias interesantes cuando consideramos agujeros negros.

 

JOURNAL CLUB

 

20/11/13

 

Speaker: Oscar Bedoya

 

Natural curvature for manifest T-duality

Martin Polacek, Warren Siegel

 

We reformulate the manifestly T-dual description of the massless sector of the closed bosonic string, directly from the geometry associated with the (left and right) affine Lie algebra of the coset space Poincare/Lorentz. This construction initially doubles not only the (spacetime) coordinates for translations but also those for Lorentz transformations (and their dual). As a result, the Lorentz connection couples directly to the string...

 

http://arxiv.org/abs/arXiv:1308.6350

 

JOURNAL CLUB

 

27/11/13

 

Speaker: Diego Marqués

 

Extended geometry and the tensor hierarchy

 

 

JOURNAL CLUB

 

Friday 6 Dic, 14H, Aula Chica

 

Speaker: Victor Penas

 

Alice falls into a black hole: Entanglement in non-inertial frames

I. Fuentes-Schuller, R. B. Mann

 

Two observers determine the entanglement between two free bosonic modes by each detecting one of the modes and observing the correlations between their measurements. We show that a state which is maximally entangled in an inertial frame becomes less entangled if the observers are relatively accelerated. This phenomenon, which is a consequence of the Unruh effect, shows that entanglement is an observer-dependent quantity in non-inertial frames. In the high acceleration limit, our results can be applied to a non-accelerated observer falling into a black hole while the accelerated one barely escapes. If the observer escapes with infinite acceleration, the state's distillable entanglement vanishes.

 

http://arxiv.org/abs/quant-ph/0410172

JOURNAL CLUB

 

Wed 11 Dic, 15H, Aula Chica

 

Speaker: Oscar Bedoya

 

On alpha-prime corrections in Heterotic Double Field Theory

 

JOURNAL CLUB

 

Fri 27 Dic, 14H, Aula Chica

 

Speaker: Mario Galante

 

Effective Field Theory for Inflation

Steven Weinberg

 

http://arxiv.org/abs/arXiv:0804.4291

 

&

 

Power-counting and the Validity of the Classical Approximation During Inflation

C.P. Burgess, Hyun Min Lee, Michael Trott

 

http://arxiv.org/abs/arXiv:0902.4465

 

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