arXiv subjects

Oscar Varela

Publications and source records attributed to Oscar Varela.

53 records · Page 3Linked to original sources

arXiv2013

Charged black rings from inverse scattering

The inverse scattering method of Belinsky and Zakharov is a powerful method to construct solutions of vacuum Einstein equations. In particular, in five dimensions this method has been successfully applied to construct a large variety of black hole solutions. Recent applications of this method to Einstein-Maxwell-dilaton (EMd) theory, for the special case of Kaluza-Klein dilaton coupling, has led to the construction of the most general black ring in this theory. In this contribution, we review the inverse scattering method and its application to the EMd theory. We illustrate the efficiency of these methods with a detailed construction of an electrically charged black ring.

hep-th↗

arXiv2012

An electrically charged doubly spinning dipole black ring

We present a new asymptotically flat, doubly spinning black ring of D = 5 Einstein-Maxwell-dilaton theory with Kaluza-Klein dilaton coupling. Besides the mass and two angular momenta, the solution displays both electric charge and (magnetic) dipole charge. The class of solutions that are free from conical singularities is described by four parameters. We first derive the solution in six dimensions employing the inverse scattering method, thereby generalising the inverse-scattering construction by two of the current authors of Emparan's singly spinning dipole black ring. The novel black ring itself arises upon circle Kaluza-Klein reduction. We also compute the main physical properties and asymptotic charges of our new class of solutions. Finally, we present a five-parameter generalisation of our solution.

hep-th↗

arXiv2012

All homogeneous N=2 M-theory truncations with supersymmetric AdS4 vacua

We study consistent truncations of M-theory to gauged N=2 supergravity in four dimensions, based on a large class of SU(3)-structures in seven dimensions. We show that the gauging involves isometries of the vector multiplet scalar manifold as well as the Heisenberg algebra and a special isometry of the hyperscalar manifold. As a result, non-abelian gauge groups and new non-trivial scalar potentials are generated. Then we specialize to all homogeneous SU(3)-structures supporting supersymmetric AdS4 vacua. These are the Stiefel manifold V52, the Aloff-Wallach spaces N(k,l), the seven-sphere (seen as SU(4)/SU(3) or Sp(2)/Sp(1)) and the M110 and Q111 coset spaces. For each of these cases, we describe in detail the N=2 model and discuss its peculiarities.

hep-th↗

arXiv2011

Spatiotemporal amplitude-and-phase reconstruction by Fourier-transform of interference spectra of high-complex-beams

We propose a novel method to reconstruct the spatio-temporal amplitude and phase of the electric field of ultrashort laser pulses using spatially-resolved spectral interferometry. This method is based on a fiber-optic coupler interferometer that has certain advantages in comparison with standard interferometer systems, such as it being alignment-free and selection of the reference beam at a single point. Our technique, which we refer to as STARFISH, offers compactness and simplicity. We report its application to the experimental characterization of chirped pulses and to spatio-temporal reconstructions of a convergent beam as well as plane-plane and spherical-plane waves interferences, which we check with our simulations.

physics.optics↗

arXiv2011

Consistent reductions from D=11 beyond Sasaki-Einstein

The most general class of warped AdS5 x M6 supersymmetric solutions in D=11 supergravity permit a consistent truncation to D=5 N=2 minimal gauged supergravity. Here we extend this truncation, for a particular subclass of M6 manifolds, to D=5 N=4 gauged supergravity coupled to two vector multiplets. We obtain the reduction ansatz by T-duality of a recently discussed type IIB truncation on a generic Sasaki-Einstein five-fold, which becomes non-trivial in D=11 and displays non-standard features due to the G-structure of the internal M6. Using this truncation, we construct two new classes of warped and unwarped non-supersymmetric AdS5 M-theory backgrounds. We also comment on possible extensions of the reduction ansatz to the general class of M6 geometries.

hep-th↗

arXiv2010

Wrapped M5-branes, consistent truncations and AdS/CMT

At the level of the bosonic fields, we construct consistent Kaluza--Klein reductions of D=11 supergravity on $Σ_3\times S^4$, where $Σ_3=H^3/Γ,S^3/Γ$ or $R^3/Γ$ where $Γ$ is a discrete group of isometries. The result is the bosonic content of an N=2 D=4 gauged supergravity with a single vector multiplet and two hypermultiplets, whose scalar fields parametrise $SU(1,1)/U(1)\times G_{2(2)}/SO(4)$. %, and the gauging is only in the hypermultiplet When $Σ_3=H^3/Γ$ the D=4 theory has an $AdS_4$ vacuum which uplifts to the known supersymmetric $AdS_4\times H^3/Γ\times S^4$ solution of D=11 supergravity that describes the N=2 $d=3$ SCFT arising when M5-branes wrap SLag 3-cycles $H^3/Γ$ in Calabi-Yau three-folds. We use the KK reduction for $Σ_3=H^3/Γ$ to construct D=11 black hole solutions that describe these d=3 SCFTs at finite temperature and charge density and show that there is a superconducting instability involving a charged scalar field, and another instability involving involving neutral fields including both scalar and vector fields. We also use this KK reduction to construct a D=11 Lifshitz solution that is dual to a d=3 field theory with dynamical exponent $z\sim 39$.

hep-th↗

arXiv2010

Universal Kaluza-Klein reductions of type IIB to N=4 supergravity in five dimensions

We construct explicit consistent Kaluza-Klein reductions of type IIB supergravity on HK_4 x S^1, where HK_4 is an arbitrary four-dimensional hyper-Kaehler manifold, and on SE5, an arbitrary five-dimensional Sasaki-Einstein manifold. In the former case we obtain the bosonic action of D=5 N=4 (ungauged) supergravity coupled to two vector multiplets. For the SE_5 case we extend a known reduction, which leads to minimal D=5 N=2 gauged supergravity, to also include a multiplet of massive fields, containing the breathing mode of the SE_5. We show that the resulting D=5 action is also consistent with N=4 gauged supergravity coupled to two vector multiplets. This theory has a supersymmetric AdS_5 vacuum, which uplifts to the class of supersymmetric AdS_5 x SE_5 solutions, that spontaneously breaks N=4 to N=2, and also a non-supersymmetric AdS_5 vacuum which uplifts to a class of solutions first found by Romans.

hep-th↗

arXiv2009

Non-relativistic M-Theory solutions based on Kaehler-Einstein spaces

We present new families of non-supersymmetric solutions of D=11 supergravity with non-relativistic symmetry, based on six-dimensional Kaehler-Einstein manifolds. In constructing these solutions, we make use of a consistent reduction to a five-dimensional gravity theory coupled to a massive scalar and vector field. This theory admits a non-relativistic CFT dual with dynamical exponent z=4, which may be uplifted to D=11 supergravity. Finally, we generalise this solution and find new solutions with various z, including z=2.

hep-th↗

arXiv2009

Consistent supersymmetric Kaluza--Klein truncations with massive modes

We construct consistent Kaluza--Klein reductions of D=11 supergravity to four dimensions using an arbitrary seven-dimensional Sasaki--Einstein manifold. At the level of bosonic fields, we extend the known reduction, which leads to minimal N=2 gauged supergravity, to also include a multiplet of massive fields, containing the breathing mode of the Sasaki--Einstein space, and still consistent with N=2 supersymmetry. In the context of flux compactifications, the Sasaki--Einstein reductions are generalizations of type IIA SU(3)-structure reductions which include both metric and form-field flux and lead to a massive universal tensor multiplet. We carry out a similar analysis for an arbitrary weak G_2 manifold leading to an N=1 supergravity with massive fields. The straightforward extension of our results to the case of the seven-sphere would imply that there is a four-dimensional Lagrangian with N=8 supersymmetry containing both massless and massive spin two fields. We use our results to construct solutions of M-theory with non-relativistic conformal symmetry.

hep-th↗

arXiv2008

D=5 SU(2)xU(1) Gauged Supergravity from D=11 Supergravity

We consider the most general class of supersymmetric solutions of D=11 supergravity consisting of a warped product of AdS_5 with a six-dimensional internal manifold N_6, which are dual to N=2 super conformal field theories in d=4. For any such N_6 we construct the full non-linear Kaluza-Klein ansatz for the reduction of D=11 supergravity on N_6 down to D=5 SU(2)xU(1) gauged supergravity, at the level of the bosonic fields. This allows one to uplift any solution of the D=5 supergravity to obtain a solution of D=11 supergravity for any given N_6. Using an explicit N_6, corresponding to M5-branes wrapping holomorphic curves in a Calabi-Yau two-fold, we uplift some solutions and comment upon their interpretation.

hep-th↗

arXiv2007

Consistent Kaluza-Klein Reductions for General Supersymmetric AdS Solutions

For the most general supersymmetric solutions of type IIB supergravity consisting of a warped product of AdS_5 with a five-dimensional manifold M_5, we construct an explicit consistent Kaluza-Klein reduction on M_5 to minimal D=5 gauged supergravity. Thus, any solution of the gauged supergravity can be uplifted on M_5 to obtain an exact solution of type IIB supergravity. We also show that for general AdS_4 x SE_7 solutions, where SE_7 is a seven-dimensional Sasaki-Einstein manifold, and for a general class of supersymmetric solutions that are a warped product of AdS_4 with a seven-dimensional manifold N_7, there is an analogous consistent reduction to minimal D=4 gauged supergravity.

hep-th↗

arXiv2006

Properties of some conformal field theories with M-theory duals

By studying classes of supersymmetric solutions of D=11 supergravity with AdS_5 factors, we determine some properties of the dual four-dimensional N=1 superconformal field theories. For some explicit solutions we calculate the central charges and also the conformal dimensions of certain chiral primary operators arising from wrapped membranes. For the most general class of solutions we show that there is a consistent Kaluza-Klein truncation to minimal D=5 gauged supergravity. This latter result allows us to study some aspects of the dual strongly coupled thermal plasma with a non-zero R-charge chemical potential and, in particular, we show that the ratio of the shear viscosity to the entropy density has the universal value of 1/4 pi.

hep-th↗

arXiv2006

On the absence of BPS preonic solutions in IIA and IIB supergravities

We consider the present absence of 31 out of 32 supersymmetric solutions in supergravity i.e., of solutions describing BPS preons. A recent result indicates that (bosonic) BPS preonic solutions do not exist in type IIB supergravity. We reconsider this analysis by using the G-frame method, extend it to the IIA supergravity case, and show that there are no (bosonic) preonic solutions for type IIA either. For the classical D=11 supergravity no conclusion can be drawn yet, although the negative IIA results permit establishing the conditions that preonic solutions would have to satisfy. For supergravities with `stringy' corrections, the existence of BPS preonic solutions remains fully open.

hep-th↗

arXiv2006

Symmetry and holonomy in M Theory

In this PhD Thesis, supersymmetry and its formulation in the context of D=11 supergravity is discussed from several perspectives. The role of generalized holonomy as a classification tool of supersymmetric supergravity solutions is reviewed, with particular emphasis on how successive supercovariant derivatives of the generalized curvature may be needed to properly define the generalized holonomy algebra. The generalized curvature is also shown to contain the supergravity equations of motion, even in the non-vanishing gravitino case. The underlying gauge symmetry of D=11 supergravity is discussed and argued to become manifest when its three-form field A_3 is expressed through a set of one-form gauge fields, associated with the generators of a suitable family of enlarged supersymmetry algebras. This family is related to osp(1|32) through expansion, a method to obtain new Lie (super)algebras of increasing dimensions from given ones. The analysis of the underlying gauge symmetry of D=11 supergravity leads naturally to enlarged supersymmetry algebras and superspaces making, thus, natural to consider actions for objects moving in such spaces. In particular, a string moving in tensorial space is discussed, describing the excitations of a state preserving 30 out of 32 supersymmetries (hence composed of two preons, hypothetical constituents of M Theory preserving 31 supersymmetries). A G-frame method is also discussed to study hypothetical preonic solutions of supergravity.

hep-th↗

arXiv2005

On the formulation of D=11 supergravity and the composite nature of its three-from field

The underlying gauge group structure of the D=11 Cremmer-Julia-Scherk supergravity becomes manifest when its three-form field A_3 is expressed through a set of one-form gauge fields. These are associated with the generators of the elements of a family of enlarged supersymmetry algebras $\tilde{\mathfrak{E}}^{(528|32+32)}(s)$ parametrized by a real number s. We study in detail the composite structure of A_3 extending previous results by D'Auria and Fré, stress the equivalence of the above problem to the trivialization of a standard supersymmetry algebra ${\mathfrak{E}}^{(11|32)}$ cohomology four-cocycle on the enlarged ${\tilde {\mathfrak{E}}}^{(528|32+32)}(s)$ superalgebras, and discuss its possible dynamical consequences. To this aim we consider the properties of the first order supergravity action with a composite A_3 field and find the set of extra gauge symmetries that guarantee that the field theoretical degrees of freedom of the theory remain the same as with a fundamental A_3. The extra gauge symmetries are also present in the so-called rheonomic treatment of the first order D=11 supergravity action when A_3 is composite. Our considerations on the composite structure of A_3 provide one more application of the idea that there exists an extended superspace coordinates/fields correspondence. They also suggest that there is a possible embedding of D=11 supergravity into a theory defined on the enlarged superspace ${\tildeΣ}^{(528|32+32)}(s)$.

hep-th↗

arXiv2004

Higher Order Integrability in Generalized Holonomy

Supersymmetric backgrounds in M-theory often involve four-form flux in addition to pure geometry. In such cases, the classification of supersymmetric vacua involves the notion of generalized holonomy taking values in SL(32,R), the Clifford group for eleven-dimensional spinors. Although previous investigations of generalized holonomy have focused on the curvature \Rm_{MN}(Ω) of the generalized SL(32,R) connection Ω_M, we demonstrate that this local information is incomplete, and that satisfying the higher order integrability conditions is an essential feature of generalized holonomy. We also show that, while this result differs from the case of ordinary Riemannian holonomy, it is nevertheless compatible with the Ambrose-Singer holonomy theorem.

hep-th↗

arXiv2002

Generating Lie and gauge free differential (super)algebras by expanding Maurer-Cartan forms and Chern-Simons supergravity

We study how to generate new Lie algebras $\mathcal{G}(N_0,..., N_p,...,N_n)$ from a given one $\mathcal{G}$. The (order by order) method consists in expanding its Maurer-Cartan one-forms in powers of a real parameter $λ$ which rescales the coordinates of the Lie (super)group $G$, $g^{i_p} \to λ^p g^{i_p}$, in a way subordinated to the splitting of $\mathcal{G}$ as a sum $V_0 \oplus ... \oplus V_p \oplus ... \oplus V_n$ of vector subspaces. We also show that, under certain conditions, one of the obtained algebras may correspond to a generalized İnönü-Wigner contraction in the sense of Weimar-Woods, but not in general. The method is used to derive the M-theory superalgebra, including its Lorentz part, from $osp(1|32)$. It is also extended to include gauge free differential (super)algebras and Chern-Simons theories, and then applied to D=3 CS supergravity.

hep-th↗