294 research outputs found

### Branes in Anti de Sitter Space-Time

An intense study of the relationship between certain quantum theories of
gravity realized on curved backgrounds and suitable gauge theories, has been
originated by a remarkable conjecture put forward by Maldacena almost one year
ago. Among the possible curved vacua of superstring or M-theory, spaces having
the form of an Anti-de Sitter space-time times a compact Einstein manifold,
have been playing a special role in this correspondence, since the quantum
theory realized on them, in the original formulation of the conjecture, was
identified with the effective superconformal theory on the world volume of
parallel p-branes set on the boundary of such a space (holography). An
important step in order to verify such a conjecture and eventually generalize
it, consists in a precise definition of the objects entering both sides of the
holographic correspondence. In the most general case indeed it turns out that
important features of the field theory on the boundary of the curved
background, identified with the quantum theory of gravity in the bulk, are
encoded in the dynamics of the coinciding parallel p-branes set on the boundary
of the same space. The study of p-brane dynamics in curved space-times which
are vacua of superstring of M-theory, turns out therefore to be a relevant
issue in order to verify the existence of the holographic correspondence. In
the present paper, besides providing a hopefully elementary introduction to
Maldacena's duality,
I shall deal in a tentatively self contained way with a particular aspect of
the problem of p-brane dynamics in Anti-de Sitter space-time, discussing some
recent results.Comment: Talk given at the XII Congress of General Relativity (SIGRAV), Bari
21-25 Sept. 1998, 1 LaTeX file, 16 page

### N=8 BPS black holes preserving 1/8 supersymmetry

In the context of N=8 supergravity we consider BPS black-holes that preserve
1/8 supersymmetry. It was shown in a previous paper that, modulo U-duality
transformations of E_{7(7)} the most general solution of this type can be
reduced to a black-hole of the STU model. In this paper we analize this
solution in detail, considering in particular its embedding in one of the
possible Special K\"ahler manifold compatible with the consistent truncations
to N=2 supergravity, this manifold being the moduli space of the T^6/Z^3
orbifold, that is: SU(3,3)/SU(3)*U(3). This construction requires a crucial use
of the Solvable Lie Algebra formalism. Once the group-theoretical analisys is
done, starting from a static, spherically symmetric ans\"atz, we find an exact
solution for all the scalars (both dilaton and axion-like) and for gauge
fields, together with their already known charge-dependent fixed values, which
yield a U-duality invariant entropy. We give also a complete translation
dictionary between the Solvable Lie Algebra and the Special K\"ahler formalisms
in order to let comparison with other papers on similar issues being more
immediate. Although the explicit solution is given in a simplified case where
the equations turn out to be more manageable, it encodes all the features of
the more general one, namely it has non-vanishing entropy and the scalar fields
have a non-trivial radial dependence.Comment: 29+1 pages, 1 Latex file; a misprint in the entropy formula,
eq.(5.14), correcte

### Unusual gauged supergravities from type IIA and type IIB orientifolds

We analyse different N=4 supergravities coupled to six vector multiplets
corresponding to low-energy descriptions of the bulk sector of T6/Z2
orientifolds with p-brane in IIB (p odd) and in IIA (p even) superstrings. When
fluxes are turned on, a gauging emerges corresponding to some non-semisimple
Lie algebra related to nilpotent algebras N_p inside so(6,6), with dimension 15
+ (p-3)(9-p). The non-metric axions have Stueckelberg couplings that induce a
spontaneous breaking of gauge symmetries. In four cases the gauge algebra is
non-abelian with a non-commutative structure of the compactification torus, due
to fluxes of NS-NS and R-R forms.Comment: 13 pages, LaTe

### Evidence for a family of SO(8) gauged supergravity theories

In this note we discuss the classification of duality orbits of N = 8 gauged
supergravity models. Using tensor classifiers, we show that there is a
one-parameter family of inequivalent SO(8) gauged supergravity theories. We
briefly discuss the couplings of such models and show that, although the
maximally symmetric vacuum has the same quadratic spectrum, the supersymmetry
transformations, the couplings and the scalar potential are parameter
dependent. We also comment on the possible M-theory uplift and on the meaning
of the parameter for the dual gauge theories.Comment: 5 pages, 2 figures. v2: improved presentation. References fixe

### Orientifolds, Brane Coordinates and Special Geometry

We report on the gauged supergravity analysis of Type IIB vacua on K3x T2/Z2
orientifold in the presence of D3-D7-branes and fluxes. We discuss
supersymmetric critical points correspond to Minkowski vacua and the related
fixing of moduli, finding agreement with previous analysis. An important role
is played by the choice of the symplectic holomorphic sections of special
geometry which enter the computation of the scalar potential. The related
period matrix N is explicitly given. The relation between the special geometry
and the Born--Infeld action for the brane moduli is elucidated.Comment: 24 pages, contribution to the proceedings of "DeserFest", Ann Arbor,
Michigan, 3-6 April 200

### Spontaneously broken supergravity: Old and new facts

We report on some recent investigations of the structure of the four
dimensional gauged supergravity Lagrangian which emerges from flux and
Scherk-Schwarz compactifications in higher dimensions. Special attention is
given to the gauge structure of M-theory compactified on a seven torus with
4-form and geometrical (spin connection) fluxes turned on. A class of vacua,
with flat space-time and described by ``no-scale'' supergravity models, is
analyzed.Comment: 14 pages, LaTeX file, imprecise statement correcte

### The $c$-map, Tits Satake subalgebras and the search for $\mathcal{N}=2$ inflaton potentials

In this paper we address the general problem of including inflationary models
exhibiting Starobinsky-like potentials into (symmetric) $\mathcal{N}=2$
supergravities. This is done by gauging suitable abelian isometries of the
hypermultiplet sector and then truncating the resulting theory to a single
scalar field. By using the characteristic properties of the global symmetry
groups of the $\mathcal{N}=2$ supergravities we are able to make a general
statement on the possible $\alpha$-attractor models which can obtained upon
truncation. We find that in symmetric $\mathcal{N}=2$ models group theoretical
constraints restrict the allowed values of the parameter $\alpha$ to be
$\alpha=1,\,\frac{2}{3},\, \frac{1}{3}$. This confirms and generalizes results
recently obtained in the literature. Our analysis heavily relies on the
mathematical structure of symmetric $\mathcal{N}=2$ supergravities, in
particular on the so called $c$-map connection between Quaternionic K\"ahler
manifolds starting from Special K\"ahler ones. A general statement on the
possible consistent truncations of the gauged models, leading to
Starobinsky-like potentials, requires the essential help of Tits Satake
universality classes. The paper is mathematically self-contained and aims at
presenting the involved mathematical structures to a public not only of
physicists but also of mathematicians. To this end the main mathematical
structures and the general gauging procedure of $\mathcal{N}=2$ supergravities
is reviewed in some detail.Comment: 101 pages, LaTeX sourc

### Black hole solutions to the $F_4$-model and their orbits (I)

In this paper we continue the program of the classification of nilpotent
orbits using the approach developed in arXiv:1107.5986, within the study of
black hole solutions in D=4 supergravities. Our goal in this work is to
classify static, single center black hole solutions to a specific N=2 four
dimensional "magic" model, with special K\"ahler scalar manifold ${\rm
Sp}(6,\mathbb{R})/{\rm U}(3)$, as orbits of geodesics on the
pseudo-quaternionic manifold ${\rm F}_{4(4)}/[{\rm SL}(2,\mathbb{R})\times {\rm
Sp}(6,\mathbb{R})]$ with respect to the action of the isometry group ${\rm
F}_{4(4)}$. Our analysis amounts to the classification of the orbits of the
geodesic "velocity" vector with respect to the isotropy group $H^*={\rm
SL}(2,\mathbb{R})\times {\rm Sp}(6,\mathbb{R})$, which include a thorough
classification of the \emph{nilpotent orbits} associated with extremal
solutions and reveals a richer structure than the one predicted by the
$\beta-\gamma$ labels alone, based on the Kostant Sekiguchi approach. We
provide a general proof of the conjecture made in arXiv:0908.1742 which states
that regular single center solutions belong to orbits with coinciding
$\beta-\gamma$ labels. We also prove that the reverse is not true by finding
distinct orbits with the same $\beta-\gamma$ labels, which are distinguished by
suitably devised tensor classifiers. Only one of these is generated by regular
solutions. Since regular static solutions only occur with nilpotent degree not
exceeding 3, we only discuss representatives of these orbits in terms of black
hole solutions. We prove that these representatives can be found in the form of
a purely dilatonic four-charge solution (the generating solution in D=3) and
this allows us to identify the orbit corresponding to the regular
four-dimensional metrics.Comment: 81 pages, 24 tables, new section 4.4 about the fake superpotential
added, typos corrected, references added, accepted in Nuclear Physics B.

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