# NEW YEAR (SUPER)GRAVITY 2018

## List of speakers

• Jose J. Fernández-Melgarejo (UM-YITP Kyoto University)
• Álvaro García Navarro (UM)
• Miguel Ángel Javaloyes (UM)
• Óscar Lasso (IFT/UAM-CSIC)
• Alessio Marrani ("Enrico Fermi" Center, Italy)
• Iván Martínez-Soler (IFT/UAM-CSIC)
• Javier Molina-Vilaplana (UPCT)
• Tomás Ortín (IFT/UAM-CSIC)*
• Alejandro Ruipérez (IFT/UAM-CSIC)
• Néstor Sánchez (UM)
• Emilio Torrente-Luján (UM)

## Program (including slides)

### January, 19th

• 09:15 - 09:30 - Torrente-Luján: Supergravity in Murcia
• 09:30 - 10:00 - Javaloyes: An overview about Finsler spacetimes and Penrose's Singularity Theorem
• 10:00 - 10:30 - Molina-Vilaplana: Entanglement Renormalization and Two Dimensional String Theory
• 10:30 - 11:00 - Lasso: RG-2 flow, Mass and Entropy

• 11:00 - 11:30 - Coffee break

• 11:30 - 12:00 - Marrani: A Mystery of Black Hole Entropy
• 12:00 - 12:30 - Ruipérez: Non-Abelian microstate geometries
• 12:30 - 12:45 - García Navarro: Beyond Einstein: Einstein-Maxwell and Brans Dicke
• 12:45 - 13:15 - Torrente-Luján: Non-Abelian Hydrodynamics: The dimensional reduction and embedding tensor approaches

• 13:15 - 15:00 - Lunch

• 15:00 - 15:30 - Sánchez: Characterization of Galactic star clusters
• 15:30 - 16:00 - Martínez-Soler: Updated fit to three neutrino mixing: exploring the accelerator-reactor complementarity

• 16:00 - 16:15 - Coffee break

• 16:15 - 16:45 - Menchón: Wormholes in Born-Infeld gravity coupled to an anisotropic fluid.
• 16:45 - 17:15 - Fernández-Melgarejo: The Odd story of \alpha'-corrections

## Abstracts

#### Fernández-Melgarejo: The Odd story of \alpha' corrections

Double Field Theory (DFT) is a T-duality symmetric formulation of 10D supergravity theories. Being T-duality a perturbative duality, one can naturally ask whether such a similar O(D,D) covariantisation also occurs in the \alpha'-corrected supergravity action. In this talk we will review the higher-derivative extension of DFT which accommodates the first order corrections of heterotic and bosonic strings in a unified framework. As an application of this formalism, we will explain how to compute higher-derivative corrections to gauged supergravities through generalised Scherk-Schwarz compactifications of the \alpha'-corrected DFT. The final and novel result will be the full alpha'-corrected action of half-maximal gauged supergravities. Based on [arXiv:1709.02388 [hep-th]].

#### García-Navarro: Beyond Einstein: Einstein-Maxwell and Brans Dicke

In this talk we will review the main aspects of General Relativity and the importance of having objects that transform covariantly under general coordinate transformations. We will study some black-hole type solutions of Einstein and Einstein-Maxwell theories, as Schwarzschild and Reissner-Nordstrom. Finally, we will introduce the Brans-Dicke theory, which is an example of a scalar-tensor gravitational theory. Here, the gravitational interaction is mediated by a scalar field as well as the tensor field of General Relativity.

#### Javaloyes: An overview about Finsler spacetimes and Penrose's Singularity Theorem

Finsler Geometry comes into play in the presence of anisotropy, which means that locally not all the directions are indistinguishable. The lack of anisotropy of the universe has been recently conjectured in the frame of the Extended Standard Model, which motivates the study of Finsler spacetimes. We will first discuss the different definitions of Finsler spacetimes and how they have been used throughout the years. Then we will show how it is possible to generalize Penrose’s Singularity Theorem to a very general class of Finsler spacetimes.

#### Lasso-Andino: RG-2 flow, Mass and Entropy

Geometric flows are used in some branches of pure mathematics. Calculating the evolution of a Riemannian metric and exploiting the monotonicity under the flow of some appropriately constructed geometric quantities mathematicians are able to find bounds and uniqueness results. One of the spectacular result is the proof of the Thurston geometrization conjecture, with the help of the Ricci flow. The flows have also been used in the context of mathematical physics, the riemannian Penrose inequality is a prominent example were the inverse mean curvature flow was employed. Those techniques are very powerful and can be used for understanding deep aspects of any geometric theory. I will show how to use the RG-2 flow for determining monotonicity and bounds for geometrical quantities such as the area and the Hawking mass. This RG-2 flow is the two loop approximation for the renormalization group flow of the quantized nonlinear sigma model. I will also discuss the relationship between differentflows and some applications. Finally I will talk about new approaches to open problems.

#### Marrani: A Mystery of Black Hole Entropy

Freudenthal duality can be defined as an anti-involutive, non-linear map acting on symplectic spaces. After a general introduction on some aspects of extended (super)gravity theories in four dimensions and the structure of their U-orbits, I will consider their U-duality Lie groups "of type E7", and the corresponding notion of Freudenthal duality. I will elucidate and comment on the relation between the Hessian of the black hole entropy and the pseudo-Riemannian, rigid, para-special Kaehler metric of the pre-homogeneous vector spaces associated to the U-orbits. I will conclude with recent developments, including the extension to Abelian gaugings of supergravity (also in presence of hypermultiplets).

#### Martínez-Soler: Updated fit to three neutrino mixing: exploring the accelerator-reactor complementarity

We perform a combined fit to global neutrino oscillation data available as of fall 2016 in the scenario of three-neutrino oscillations and present updated allowed ranges of the six oscillation parameters. We discuss the differences arising between the consistent combination of the data samples from accelerator and reactor experiments compared to partial combinations. We quantify the confidence in the determination of the less precisely known parameters θ2323, δCPCP, and the neutrino mass ordering by performing a Monte Carlo study of the long baseline accelerator and reactor data. We find that the sensitivity to the mass ordering and the θ2323 octant is below 1σ. Maximal θ2323 mixing is allowed at slightly more than 90% CL. The best fit for the CP violating phase is around 270°, CP conservation is allowed at slightly above 1σ, and values of δCPCP ≃ 90° are disfavored at around 99% CL for normal ordering and higher CL for inverted ordering.

#### Menchón: Wormholes in Born-Infeld gravity coupled to an anisotropic fluid

We study Born-Infled gravity coupled to an anisotropic fluid in a static, spherically symmetric background. The free function characterizing the fluid is selected on the following grounds: i) recovery of the Reissner-Nordström solution of GR at large distances, ii) fulfillment of classical energy conditions and iii) inclusion of models of nonlinear electrodynamics as particular examples. Four branches of solutions are obtained, depending on the signs of two parameters on the gravity and matter sectors. We discuss the modifications on the innermost region of the corresponding solutions on one of branch, which provides a plethora of configurations, including wormholes. The regular character of these configurations is discussed according to the completeness of geodesics and the behavior of curvature scalars.

#### Molina-Vilaplana: Entanglement Renormalization and Two Dimensional String Theory

In this talk, based on arXiv:1510.09020, the entanglement renormalization flow of a (1+1) free boson is formulated as a path integral over some auxiliary scalar fields. The resulting effective theory for these fields amounts to the dilaton term of non-critical string theory in two spacetime dimensions. A connection between the scalar fields in the two theories is provided, allowing to acquire novel insights into how a theory of gravity emerges from the entanglement structure of another one without gravity.

#### Ruipérez: Non-Abelian microstate geometries

Microstate geometries are smooth horizonless solutions of supergravity theories, which are claimed to represent the classical description of the microstates of a black hole. So far, no systematic procedure to construct these type of solutions was known. I will talk about the results of a recent paper (arXiv:1709.03985) in which we argue that the problem of constructing explicit solutions can be boiled down to the evaluation of an algebraic constraint, allowing us to design a systematic procedure to generate these solutions.

#### Sánchez: Characterization of Galactic star clusters

Star clusters have long been recognized as very useful tools in many areas of astronomy. A precise knowledge of cluster properties such as distance, age, metallicity or reddening is necessary in order to be able to draw reliable conclusions on, for instance, the rotation or the star formation history of our Galaxy. I will explain the main current problems when inferring cluster properties and, in particular, when estimating a particularly valuable parameter: cluster radius. I will discuss some previous interesting results and a novel method we are proposing in order to calculate the radius of an open cluster in an objective way from the proper motion of its stars.

#### Torrente-Luján: Non-Abelian Hydrodynamics: The dimensional reduction and embedding tensor approaches

Since Cho&Freund (1975) we know that the diffeormorphism group in $D=d+n$ dimensions contains d-dimensional diffeormosphisms plus n-Non-Abelian gauge transformations. This is the basis of the Scherk-Schwarz mechanism.
We present a progress report of some ongoing research about new approaches to the study of non-Abelian plasmas.
The new approach is two fold, in one case we use the dimensional reduction on a group manifold of a D-fluid neutral fluid to get a non-Abelian system at lower dimensions. In the other complementary case we study, using the embedding tensor technique, borrowed from supergravity gauged theories, all possible non-abelian deformations of a fluid system with a given field content.

The work to be presented is made in collaboration with JJ. Fernandez-Melgarejo and A. Ruiperez Vicente. It is the basis of two publications to appear, it is also related to arXiv:1605.06080.

## Banquet

TBA

### Organisation

• Jose J. Fernández-Melgarejo (Universidad de Murcia - YITP, Kyoto University)
• Emilio Torrente-Luján (Universidad de Murcia)