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George Moutsopoulos

Publications and source records attributed to George Moutsopoulos.

14 recordsLinked to original sources
arXiv2018

Critical N=(1,1) General Massive Supergravity

In this paper we study the supermultiplet structure of $\mathcal{N}=(1,1)$ General Massive Supergravity at non-critical and critical points of its parameter space. To do this, we first linearize the theory around its maximally supersymmetric AdS$_3$ vacuum and obtain the full linearized Lagrangian including fermionic terms. At generic values, linearized modes can be organized as two massless and 2 massive multiplets where supersymmetry relates them in the standard way. At critical points logarithmic modes appear and we find that in three of such points some of the supersymmetry transformations are non-invertible in logarithmic multiplets. However, in the fourth critical point, there is a massive logarithmic multiplet with invertible supersymmetry transformations.

hep-th↗
arXiv2016

Quarter-BPS solutions in three-dimensional N=16 supergravity and the Liouville equation

We show how by assuming at least 8 real timelike supersymmetries in the maximally supersymmetric three-dimensional ungauged supergravity and a further simplifying Ansatz, we are naturally led to a pair of Liouville field equations. We also show that there are no solutions that preserve only 6 real timelike supersymmetries. The solution relies on the classification of complex spinors of Spin(8) to which the problem quickly reduces.

hep-th↗
arXiv2016

Supersymmetric solutions of $N=(2,0)$ Topologically Massive Supergravity

We first make a Killing spinor analysis for a general three-dimensional off-shell $N=(2,0)$ supergravity and find conditions for a bosonic background to preserve some supersymmetry . We then consider a particular model, namely $N=(2,0)$ topologically massive supergravity and impose its field equations. By making a suitable ansatz on metric functions we find a large class of solutions that include spacelike, timelike and null warped $AdS_3$ among others. Isometric quotients of spacelike and timelike squashed $AdS_3$ solutions yield extremal black holes without closed causal curves.

hep-th↗
arXiv2016

Warped anti-de Sitter in 3d (2,0) Supergravity

We comment on the ubiquity of the so-called warped anti-de Sitter spacetimes in three-dimensional (2,0) supergravity theory. By using isometry-invariant tensors and simple counting, we prove their existence for arbitrary $(2,0)$ supergravity models suitably defined close to a minimal model. We also analyze their offshell supersymmetry and the supersymmetry of two geometric orbifolds.

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arXiv2015

All timelike supersymmetric solutions of three-dimensional half-maximal supergravity

We first classify all supersymmetric solutions of the 3-dimensional half-maximal ungauged supergravity that possess a timelike Killing vector coming from the Killing spinor bilinear by considering their identification under the complexification of the local symmetry of the theory. It is found that only solutions that preserve $16/2^n, 1 \leq n \leq 3$ real supersymmetries are allowed. We then classify supersymmetric solutions under the real local symmetry of the theory and we are able to solve the equations of motion for all of them. It is shown that all such solutions can be expressed as a direct sum of solutions of the integrable Liouville and SU(3) Toda systems. This completes the construction of all supersymmetric solutions of the model since the null case has already been solved.

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arXiv2014

Effective actions of non-geometric fivebranes

An interesting consequence of string dualities is that they reveal situations where the geometry of a string background appears to be globally ill-defined, a phenomenon usually referred to as non-geometry. On the other hand, string theory contains extended objects with non-trivial monodromy around them, often dubbed defect or exotic branes in co-dimension two. We determine and examine the worldvolume actions and the couplings of certain such branes. In particular, based on specific chains of T and S-dualities, we derive the DBI and WZ actions, which describe the dynamics of type IIB fivebranes as well as their couplings to the appropriate gauge potentials associated to mixed symmetry tensors. Based on these actions we discuss how these branes act as sources of non-geometric fluxes. In one case this flux is what is usually termed Q flux, associated to a T-fold compactification, while in the S-dual case a type of non-geometry related to the Ramond-Ramond sector is encountered.

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arXiv2013

Homogeneous anisotropic solutions of topologically massive gravity with cosmological constant and their homogeneous deformations

We solve the equations of topologically massive gravity with potentially non-vanishing cosmological constant for homogeneous metrics without isotropy. We only reproduce known solutions. We also discuss their homogeneous deformations, possibly with isotropy. We show that de Sitter space and hyperbolic space cannot be infinitesimally homogeneously deformed in TMG. We clarify some of their Segre-Petrov types and discuss the warped de Sitter spacetime.

gr-qc↗
arXiv2012

The Killing superalgebra of ten-dimensional supergravity backgrounds

We construct the Killing superalgebra of supersymmetric backgrounds of ten-dimensional heterotic and type II supergravities and prove that it is a Lie superalgebra. We also show that if the fraction of supersymmetry preserved by the background is greater than 1/2, in the heterotic case, or greater than 3/4 in the type II case, then the background is locally homogeneous.

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arXiv2012

No more CKY two-forms in the NHEK

We show that in the near-horizon limit of a Kerr-NUT-AdS black hole, the space of conformal Killing-Yano two-forms does not enhance and remains of dimension two. The same holds for an analogous polar limit in the case of extremal NUT charge. We also derive the conformal Killing-Yano $p$-form equation for any background in arbitrary dimension in the form of parallel transport.

gr-qc↗
arXiv2010

From accelerating and Poincaré coordinates to black holes in spacelike warped AdS$_3$, and back

We first review spacelike stretched warped AdS$_3$ and we describe its black hole quotients by using accelerating and Poincaré coordinates. We then describe the maximal analytic extension of the black holes and present their causal diagrams. Finally, we calculate spacetime limits of the black hole phase space $(T_R,T_L)$. This is done by requiring that the identification vector $\partial_θ$ has a finite non-zero limit. The limits we obtain are the self-dual solution in accelerating or Poincaré coordinates, depending respectively on whether the limiting spacetimes are non-extremal or extremal, and warped AdS with a periodic proper time identification.

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arXiv2010

The NUT in the N=2 Superalgebra

We study how the supersymmetry algebra extension of N=2 supergravity with central charges describes the NUT charge in a duality-covariant way. The stationary BPS states of N=2 supergravity can be embedded in the flat space solution of the timelike reduced theory. Upon reduction, the Killing superalgebra extension and the global superalgebra of charges are described covariantly under the coset structure of the three-dimensional theory. The integral of the Nester-Witten form given by Gibbons and Hull for N=2 has a covariant generalization that includes the NUT charge.

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arXiv2008

On the maximal superalgebras of supersymmetric backgrounds

In this note we give a precise definition of the notion of a maximal superalgebra of certain types of supersymmetric supergravity backgrounds, including the Freund-Rubin backgrounds, and propose a geometric construction extending the well-known construction of its Killing superalgebra. We determine the structure of maximal Lie superalgebras and show that there is a finite number of isomorphism classes, all related via contractions from an orthosymplectic Lie superalgebra. We use the structure theory to show that maximally supersymmetric waves do not possess such a maximal superalgebra, but that the maximally supersymmetric Freund-Rubin backgrounds do. We perform the explicit geometric construction of the maximal superalgebra of AdS_4 x S^7 and find that is isomorphic to osp(1|32). We propose an algebraic construction of the maximal superalgebra of any background asymptotic to AdS_4 x S^7 and we test this proposal by computing the maximal superalgebra of the M2-brane in its two maximally supersymmetric limits, finding agreement.

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arXiv2006

Quantum Mechanics of the Doubled Torus

We investigate the quantum mechanics of the doubled torus system, introduced by Hull [1] to describe T-folds in a more geometric way. Classically, this system consists of a world-sheet Lagrangian together with some constraints, which reduce the number of degrees of freedom to the correct physical number. We consider this system from the point of view of constrained Hamiltonian dynamics. In this case the constraints are second class, and we can quantize on the constrained surface using Dirac brackets. We perform the quantization for a simple T-fold background and compare to results for the conventional non-doubled torus system. Finally, we formulate a consistent supersymmetric version of the doubled torus system, including supersymmetric constraints.

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